idnits 2.17.1 draft-ietf-vrrp-ipv6-spec-08.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- ** It looks like you're using RFC 3978 boilerplate. You should update this to the boilerplate described in the IETF Trust License Policy document (see https://trustee.ietf.org/license-info), which is required now. -- Found old boilerplate from RFC 3978, Section 5.1 on line 17. -- Found old boilerplate from RFC 3978, Section 5.5, updated by RFC 4748 on line 1335. -- Found old boilerplate from RFC 3979, Section 5, paragraph 1 on line 1161. -- Found old boilerplate from RFC 3979, Section 5, paragraph 2 on line 1168. -- Found old boilerplate from RFC 3979, Section 5, paragraph 3 on line 1174. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- == No 'Intended status' indicated for this document; assuming Proposed Standard Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- ** The abstract seems to contain references ([ND]), which it shouldn't. Please replace those with straight textual mentions of the documents in question. == There are 1 instance of lines with multicast IPv4 addresses in the document. If these are generic example addresses, they should be changed to use the 233.252.0.x range defined in RFC 5771 == There are 1 instance of lines with non-RFC3849-compliant IPv6 addresses in the document. If these are example addresses, they should be changed. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust Copyright Line does not match the current year == Using lowercase 'not' together with uppercase 'MUST', 'SHALL', 'SHOULD', or 'RECOMMENDED' is not an accepted usage according to RFC 2119. Please use uppercase 'NOT' together with RFC 2119 keywords (if that is what you mean). Found 'SHOULD not' in this paragraph: When a VRRP router restarts or boots, it SHOULD not send any ND messages with its physical MAC address for the IPv6 address it owns, it should only send ND messages that include Virtual MAC addresses. This may entail: == Using lowercase 'not' together with uppercase 'MUST', 'SHALL', 'SHOULD', or 'RECOMMENDED' is not an accepted usage according to RFC 2119. Please use uppercase 'NOT' together with RFC 2119 keywords (if that is what you mean). Found 'SHOULD not' in this paragraph: A VRRP router SHOULD not forward packets addressed to the IPv6 Address it becomes Master for if it is not the owner. Forwarding these packets would result in unnecessary traffic. Also in the case of LANs that receive packets they transmit (e.g., token ring) this can result in a forwarding loop that is only terminated when the IPv6 TTL expires. -- The document seems to lack a disclaimer for pre-RFC5378 work, but may have content which was first submitted before 10 November 2008. If you have contacted all the original authors and they are all willing to grant the BCP78 rights to the IETF Trust, then this is fine, and you can ignore this comment. If not, you may need to add the pre-RFC5378 disclaimer. (See the Legal Provisions document at https://trustee.ietf.org/license-info for more information.) -- The document date (February 23, 2007) is 6269 days in the past. Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) ** Obsolete normative reference: RFC 2460 (ref. 'IPv6') (Obsoleted by RFC 8200) -- Possible downref: Non-RFC (?) normative reference: ref. 'IPX' ** Obsolete normative reference: RFC 2461 (ref. 'ND') (Obsoleted by RFC 4861) -- Possible downref: Non-RFC (?) normative reference: ref. 'TKARCH' ** Obsolete normative reference: RFC 3768 (ref. 'VRRP-V4') (Obsoleted by RFC 5798) Summary: 5 errors (**), 0 flaws (~~), 6 warnings (==), 9 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group R. Hinden 3 Internet-Draft Nokia 4 Expires: August 23, 2007 J.Cruz, Editor 5 Cisco Systems 6 February 23, 2007 8 Virtual Router Redundancy Protocol for IPv6 10 12 Status of this Memo 14 By submitting this Internet-Draft, each author represents that any 15 applicable patent or other IPR claims of which he or she is aware 16 have been or will be disclosed, and any of which he or she becomes 17 aware will be disclosed, in accordance with Section 6 of BCP 79. 19 Internet-Drafts are working documents of the Internet Engineering 20 Task Force (IETF), its areas, and its working groups. Note that 21 other groups may also distribute working documents as 22 Internet-Drafts. 24 Internet-Drafts are draft documents valid for a maximum of six months 25 and may be updated, replaced, or obsoleted by other documents at any 26 time. It is inappropriate to use Internet-Drafts as reference 27 material or to cite them other than as "work in progress." 29 The list of current Internet-Drafts can be accessed at 30 http://www.ietf.org/ietf/1id-abstracts.txt. 32 The list of Internet-Draft Shadow Directories can be accessed at 33 http://www.ietf.org/shadow.html. 35 This internet draft expires on April 3, 2005. 37 Copyright Notice 39 Copyright (C) The IETF Trust (2007). 41 Abstract 43 This memo defines the Virtual Router Redundancy Protocol (VRRP) for 44 IPv6. It is version three (3) of the protocol. It is based on the 45 original version of VRRP (version 2) for IPv4 that is defined in 46 RFC2338. 48 VRRP specifies an election protocol that dynamically assigns 49 responsibility for a virtual router to one of the VRRP routers on a 50 LAN. The VRRP router controlling the IP address(es) associated with 51 a virtual router is called the Master, and forwards packets sent to 52 these IP addresses. The election process provides dynamic fail over 53 in the forwarding responsibility should the Master become 54 unavailable. The advantage gained from using VRRP for IPv6 is a 55 quicker switch over to back up routers than can be obtained with 56 standard IPv6 Neighbor Discovery [ND] mechanisms. 58 Table of Contents 60 1. Introduction................................................3 61 2. Required Features...........................................5 62 3. VRRP Overview...............................................6 63 4. Sample Configurations.......................................8 64 5. Protocol...................................................10 65 5.1 VRRP Packet Format....................................10 66 5.2 IP Field Descriptions.................................11 67 5.3 VRRP Field Descriptions...............................11 68 6. Protocol State Machine....................................13 69 6.1 Parameters per Virtual Router.........................13 70 6.2 Timers................................................13 71 6.3 State Transition Diagram..............................15 72 6.4 State Descriptions....................................15 73 7. Sending and Receiving VRRP Packets........................19 74 7.1 Receiving VRRP Packets................................19 75 7.2 Transmitting Packets..................................19 76 7.3 Virtual MAC Address...................................20 77 7.4 IPv6 Interface Identifiers............................20 78 8. Operational Issues........................................21 79 8.1 ICMPv6 Redirects......................................21 80 8.2 ND Neighbor Solicitation..............................21 81 8.3 Router Advertisements.................................21 82 8.4 Potential Forwarding Loop.............................22 83 8.5 Recommendations regarding setting priority values.....22 84 9. Operation over FDDI, Token Ring, and ATM LANE.............22 85 9.1 Operation over FDDI...................................22 86 9.2 Operation over Token Ring.............................22 87 9.3 Operation over ATM LANE...............................25 88 10. Security Considerations...................................25 89 11. Intellectual Property.....................................26 90 12. Acknowledgments...........................................26 91 13. IANA Considerations.......................................27 92 14. Normative References......................................27 93 15. Informative References....................................28 94 16. Changes from RFC2338......................................29 96 1. Introduction 98 IPv6 hosts on a LAN will usually learn about one or more default 99 routers by receiving Router Advertisements sent using the IPv6 100 Neighbor Discovery protocol [ND]. The Router Advertisements are 101 multicast periodically at a rate that the hosts will learn about the 102 default routers in a few minutes. They are not sent frequently enough 103 to rely on the absence of the router advertisement to detect router 104 failures. 106 Neighbor Discovery (ND) includes a mechanism called Neighbor 107 Unreachability Detection to detect the failure of a neighbor node 108 (router or host) or the forwarding path to a neighbor. This is done 109 by sending unicast ND Neighbor Solicitation messages to the neighbor 110 node. To reduce the overhead of sending Neighbor Solicitations, they 111 are only sent to neighbors to which the node is actively sending 112 traffic and only after there has been no positive indication that the 113 router is up for a period of time. Using the default parameters in 114 ND, it will take a host about 38 seconds to learn that a router is 115 unreachable before it will switch to another default router. This 116 delay would be very noticeable to users and cause some transport 117 protocol implementations to timeout. 119 While the ND unreachability detection could be speeded up by changing 120 the parameters to be more aggressive (note that the current lower 121 limit for this is 5 seconds), this would have the downside of 122 significantly increasing the overhead of ND traffic. Especially when 123 there are many hosts all trying to determine the reachability of a 124 one of more routers. 126 The Virtual Router Redundancy Protocol for IPv6 provides a much 127 faster switch over to an alternate default router than can be 128 obtained using standard ND procedures. Using VRRP a backup router 129 can take over for a failed default router in around three seconds 130 (using VRRP default parameters). This is done with out any 131 interaction with the hosts and a minimum amount of VRRP traffic. 133 VRRP specifies an election protocol that dynamically assigns 134 responsibility for a virtual router to one of the VRRP routers on a 135 LAN. The VRRP router controlling the IP address(es) associated with 136 a virtual router is called the Master, and forwards packets sent to 137 these IP addresses. The election process provides dynamic fail over 138 in the forwarding responsibility should the Master become 139 unavailable. 141 VRRP provides a function similar to the proprietary protocols Hot 142 Standby Router Protocol (HSRP) [HSRP] and IP Standby Protocol 143 [IPSTB]. 145 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 146 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 147 document are to be interpreted as described in [RFC2119]. 149 1.1 Scope 151 The remainder of this document describes the features, design goals, 152 and theory of operation of VRRP for IPv6. The message formats, 153 protocol processing rules and state machine that guarantee 154 convergence to a single Virtual Router Master are presented. 155 Finally, operational issues related to MAC address mapping, handling 156 of Neighbor Discovery requests, generation of ICMPv6 redirect 157 messages, and security issues are addressed. 159 This protocol is intended for use with IPv6 routers only. VRRP for 160 IPv4 is defined in [VRRP-V4]. 162 1.2 Definitions 164 VRRP Router A router running the Virtual Router Redundancy 165 Protocol. It may participate in one or more 166 virtual routers. 168 Virtual Router An abstract object managed by VRRP that acts 169 as a default router for hosts on a shared LAN. 170 It consists of a Virtual Router Identifier and 171 an a set of associated IPv6 address(es) across 172 a common LAN. A VRRP Router may backup one or 173 more virtual routers. 175 IPv6 Address Owner The VRRP router that has the virtual router's 176 IPv6 address(es) as real interface address. 177 This is the router that, when up, will respond 178 to packets addressed to the IPv6 address(es) 179 for ICMPv6 pings, TCP connections, etc. 181 Virtual Router Master The VRRP router that is assuming the 182 responsibility of forwarding packets sent to 183 the IPv6 address(es) associated with the 184 virtual router, and answering ND requests for 185 these IPv6 address(es). Note that if the IPv6 186 address owner is available, then it will 187 always become the Master. 189 Virtual Router Backup The set of VRRP routers available to assume 190 forwarding responsibility for a virtual router 191 should the current Master fail. 193 2.0 Required Features 195 This section outlines the set of features that were considered 196 mandatory and that guided the design of VRRP. 198 2.1 IPv6 Address Backup 200 Backup of an IPv6 address(es) is the primary function of the Virtual 201 Router Redundancy Protocol. While providing election of a Virtual 202 Router Master and the additional functionality described below, the 203 protocol should strive to: 205 - Minimize the duration of black holes. 206 - Minimize the steady state bandwidth overhead and processing 207 complexity. 208 - Function over a wide variety of multiaccess LAN technologies 209 capable of supporting IPv6 traffic. 210 - Provide for election of multiple virtual routers on a network for 211 load balancing 212 - Support of multiple logical IPv6 subnets on a single LAN segment. 214 2.2 Preferred Path Indication 216 A simple model of Master election among a set of redundant routers is 217 to treat each router with equal preference and claim victory after 218 converging to any router as Master. However, there are likely to be 219 many environments where there is a distinct preference (or range of 220 preferences) among the set of redundant routers. For example, this 221 preference may be based upon access link cost or speed, router 222 performance or reliability, or other policy considerations. The 223 protocol should allow the expression of this relative path preference 224 in an intuitive manner, and guarantee Master convergence to the most 225 preferential router currently available. 227 2.3 Minimization of Unnecessary Service Disruptions 229 Once Master election has been performed then any unnecessary 230 transitions between Master and Backup routers can result in a 231 disruption in service. The protocol should ensure after Master 232 election that no state transition is triggered by any Backup router 233 of equal or lower preference as long as the Master continues to 234 function properly. 236 Some environments may find it beneficial to avoid the state 237 transition triggered when a router becomes available that is 238 preferred over the current Master. It may be useful to support an 239 override of the immediate convergence to the preferred path. 241 2.4 Efficient Operation over Extended LANs 243 Sending IPv6 packets on a multiaccess LAN requires mapping from an 244 IPv6 address to a MAC address. The use of the virtual router MAC 245 address in an extended LAN employing learning bridges can have a 246 significant effect on the bandwidth overhead of packets sent to the 247 virtual router. If the virtual router MAC address is never used as 248 the source address in a link level frame then the station location is 249 never learned, resulting in flooding of all packets sent to the 250 virtual router. To improve the efficiency in this environment the 251 protocol should: 1) use the virtual router MAC as the source in a 252 packet sent by the Master to trigger station learning; 2) trigger a 253 message immediately after transitioning to Master to update the 254 station learning; and 3) trigger periodic messages from the Master to 255 maintain the station learning cache. 257 3.0 VRRP Overview 259 VRRP specifies an election protocol to provide the virtual router 260 function described earlier. All protocol messaging is performed 261 using IPv6 multicast datagrams, thus the protocol can operate over a 262 variety of multiaccess LAN technologies supporting IPv6 multicast. 263 Each VRRP virtual router has a single well-known MAC address 264 allocated to it. This document currently only details the mapping to 265 networks using the IEEE 802 48-bit MAC address. The virtual router 266 MAC address is used as the source in all periodic VRRP messages sent 267 by the Master router to enable bridge learning in an extended LAN. 269 A virtual router is defined by its virtual router identifier (VRID) 270 and a set of IPv6 address(es). A VRRP router may associate a virtual 271 router with its real address on an interface, and may also be 272 configured with additional virtual router mappings and priority for 273 virtual routers it is willing to backup. The mapping between VRID 274 and its IPv6 address(es) must be coordinated among all VRRP routers 275 on a LAN. However, there is no restriction against reusing a VRID 276 with a different address mapping on different LANs. The scope of 277 each virtual router is restricted to a single LAN. 279 To minimize network traffic, only the Master for each virtual router 280 sends periodic VRRP Advertisement messages. A Backup router will not 281 attempt to preempt the Master unless it has higher priority. This 282 eliminates service disruption unless a more preferred path becomes 283 available. It's also possible to administratively prohibit all 284 preemption attempts. The only exception is that a VRRP router will 285 always become Master of any virtual router associated with address it 286 owns. If the Master becomes unavailable then the highest priority 287 Backup will transition to Master after a short delay, providing a 288 controlled transition of the virtual router responsibility with 289 minimal service interruption. 291 The VRRP protocol design provides rapid transition from Backup to 292 Master to minimize service interruption, and incorporates 293 optimizations that reduce protocol complexity while guaranteeing 294 controlled Master transition for typical operational scenarios. The 295 optimizations result in an election protocol with minimal runtime 296 state requirements, minimal active protocol states, and a single 297 message type and sender. The typical operational scenarios are 298 defined to be two redundant routers and/or distinct path preferences 299 among each router. A side effect when these assumptions are violated 300 (i.e., more than two redundant paths all with equal preference) is 301 that duplicate packets may be forwarded for a brief period during 302 Master election. However, the typical scenario assumptions are 303 likely to cover the vast majority of deployments, loss of the Master 304 router is infrequent, and the expected duration in Master election 305 convergence is quite small ( << 1 second ). Thus the VRRP 306 optimizations represent significant simplifications in the protocol 307 design while incurring an insignificant probability of brief network 308 degradation. 310 4. Sample Configurations 312 4.1 Sample Configuration 1 314 The following figure shows a simple network with two VRRP routers 315 implementing one virtual router. Note that this example is provided 316 to help understand the protocol, but is not expected to occur in 317 actual practice. 319 +-----------+ +-----------+ 320 | Rtr1 | | Rtr2 | 321 |(MR VRID=1)| |(BR VRID=1)| 322 | | | | 323 VRID=1 +-----------+ +-----------+ 324 IPv6 A -------->* *<--------- IPv6 B 325 | | 326 | | 327 ------------------+------------+-----+--------+--------+--------+-- 328 ^ ^ ^ ^ 329 | | | | 330 (IPv6 A) (IPv6 A) (IPv6 A) (IPv6 A) 331 | | | | 332 +--+--+ +--+--+ +--+--+ +--+--+ 333 | H1 | | H2 | | H3 | | H4 | 334 +-----+ +-----+ +--+--+ +--+--+ 335 Legend: 336 ---+---+---+-- = Ethernet, Token Ring, or FDDI 337 H = Host computer 338 MR = Master Router 339 BR = Backup Router 340 * = IPv6 Address 341 (IPv6) = default router for hosts 343 Eliminating all mention of VRRP (VRID=1) from the figure above leaves 344 it as a typical IPv6 deployment. Each router has a link-local IPv6 345 address on the LAN interface (Rtr1 is assigned IPv6 Link-Local A and 346 Rtr2 is assigned IPv6 Link-Local B), and each host learns a default 347 route from Router Advertisements through one of the routers (in this 348 example they all use Rtr1's IPv6 Link-Local A). 350 Moving to the VRRP environment, each router has the exact same Link- 351 Local IPv6 address. Rtr1 is said to be the IPv6 address owner of 352 IPv6 A, and Rtr2 is the IPv6 address owner of IPv6 B. A virtual 353 router is then defined by associating a unique identifier (the 354 virtual router ID) with the address owned by a router. Finally, the 355 VRRP protocol manages virtual router fail over to a backup router. 357 The example above shows a virtual router configured to cover the IPv6 358 address owned by Rtr1 (VRID=1,IPv6_Address=A). When VRRP is enabled 359 on Rtr1 for VRID=1 it will assert itself as Master, with 360 priority=255, since it is the IPv6 address owner for the virtual 361 router IPv6 address. When VRRP is enabled on Rtr2 for VRID=1 it will 362 transition to Backup, with priority=100, since it is not the IPv6 363 address owner. If Rtr1 should fail then the VRRP protocol will 364 transition Rtr2 to Master, temporarily taking over forwarding 365 responsibility for IPv6 A to provide uninterrupted service to the 366 hosts. 368 Note that in this example IPv6 B is not backed up, it is only used by 369 Rtr2 as its interface address. In order to backup IPv6 B, a second 370 virtual router must be configured. This is shown in the next 371 section. 373 4.2 Sample Configuration 2 375 The following figure shows a configuration with two virtual routers 376 with the hosts splitting their traffic between them. This example is 377 expected to be common in actual practice. 379 +-----------+ +-----------+ 380 | Rtr1 | | Rtr2 | 381 |(MR VRID=1)| |(BR VRID=1)| 382 |(BR VRID=2)| |(MR VRID=2)| 383 VRID=1 +-----------+ +-----------+ VRID=2 384 IPv6 A -------->* *<---------- IPv6 B 385 | | 386 | | 387 ------------------+------------+-----+--------+--------+--------+-- 388 ^ ^ ^ ^ 389 | | | | 390 (IPv6 A) (IPv6 A) (IPv6 B) (IPv6 B) 391 | | | | 392 +--+--+ +--+--+ +--+--+ +--+--+ 393 | H1 | | H2 | | H3 | | H4 | 394 +-----+ +-----+ +--+--+ +--+--+ 395 Legend: 396 ---+---+---+-- = Ethernet, Token Ring, or FDDI 397 H = Host computer 398 MR = Master Router 399 BR = Backup Router 400 * = IPv6 Address 401 (IPv6) = default router for hosts 403 In the example above, half of the hosts have learned a default route 404 through Rtr1's IPv6 A and half are using Rtr2's IPv6 B. The 405 configuration of virtual router VRID=1 is exactly the same as in the 406 first example (see section 4.1), and a second virtual router has been 407 added to cover the IPv6 address owned by Rtr2 (VRID=2, 408 IPv6_Address=B). In this case Rtr2 will assert itself as Master for 409 VRID=2 while Rtr1 will act as a backup. This scenario demonstrates a 410 deployment providing load splitting when both routers are available 411 while providing full redundancy for robustness. 413 5.0 Protocol 415 The purpose of the VRRP packet is to communicate to all VRRP routers 416 the priority and the state of the Master router associated with the 417 Virtual Router ID. 419 VRRP packets are sent encapsulated in IPv6 packets. They are sent to 420 the IPv6 multicast address assigned to VRRP. 422 5.1 VRRP Packet Format 424 This section defines the format of the VRRP packet and the relevant 425 fields in the IPv6 header. 427 0 1 2 3 428 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 429 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 430 |Version| Type | Virtual Rtr ID| Priority |Count IPv6 Addr| 431 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 432 |(rsvd) | Adver Int | Checksum | 433 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 434 | | 435 + + 436 | IPv6 Address(es) | 437 + + 438 + + 439 + + 440 + + 441 | | 442 + + 443 | | 444 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 446 5.2 IPv6 Field Descriptions 448 5.2.1 Source Address 450 The IPv6 link-local address of the interface the packet is being sent 451 from. 453 5.2.2 Destination Address 455 The IPv6 multicast address as assigned by the IANA for VRRP is: 457 FF02:0:0:0:0:0:XXXX:XXXX 459 This is a link-local scope multicast address. Routers MUST NOT 460 forward a datagram with this destination address regardless of its 461 Hop Limit. 463 5.2.3 Hop Limit 465 The Hop Limit MUST be set to 255. A VRRP router receiving a packet 466 with the Hop Limit not equal to 255 MUST discard the packet. 468 5.2.4 Next Header 470 The IPv6 Next Header protocol assigned by the IANA for VRRP is 112 471 (decimal). 473 5.3 VRRP Field Descriptions 475 5.3.1 Version 477 The version field specifies the VRRP protocol version of this packet. 478 This document defines version 3. 480 5.3.2 Type 482 The type field specifies the type of this VRRP packet. The only 483 packet type defined in this version of the protocol is: 485 1 ADVERTISEMENT 487 A packet with unknown type MUST be discarded. 489 5.3.3 Virtual Rtr ID (VRID) 491 The Virtual Router Identifier (VRID) field identifies the virtual 492 router this packet is reporting status for. 494 5.3.4 Priority 496 The priority field specifies the sending VRRP router's priority for 497 the virtual router. Higher values equal higher priority. This field 498 is an 8 bit unsigned integer field. 500 The priority value for the VRRP router that owns the IPv6 address 501 associated with the virtual router MUST be 255 (decimal). 503 VRRP routers backing up a virtual router MUST use priority values 504 between 1-254 (decimal). The default priority value for VRRP routers 505 backing up a virtual router is 100 (decimal). 507 The priority value zero (0) has special meaning indicating that the 508 current Master has stopped participating in VRRP. This is used to 509 trigger Backup routers to quickly transition to Master without having 510 to wait for the current Master to timeout. 512 5.3.5 Count IPv6 Addr 514 The number of IPv6 addresses contained in this VRRP advertisement. 515 The minimum value is 1. 517 5.3.5 Rsvd 519 This field MUST be set to zero on transmission and ignored on 520 reception. 522 5.3.6 Advertisement Interval (Adver Int) 524 The Advertisement interval is a 12-bit field that indicates the time 525 interval (in centiseconds) between ADVERTISEMENTS. The default is 526 100 centiseconds (1 second). This field is used for troubleshooting 527 misconfigured routers. 529 5.3.7 Checksum 531 The checksum field is used to detect data corruption in the VRRP 532 message. 534 The checksum is the 16-bit one's complement of the one's complement 535 sum of the entire VRRP message starting with the version field and a 536 "pseudo-header" as defined in section 8.1 of RFC2460 [IPv6]. The 537 next header field in the "pseudo-header" should be set to 112 538 (decimal) for VRRP. For computing the checksum, the checksum field 539 is set to zero. See RFC1071 for more detail [CKSM]. 541 5.3.8 IPv6 Address(es) 543 One or more IPv6 addresses associated associated with the virtual 544 router. The number of addresses included is specified in the "Count 545 IP Addr" field. The first address must be the IPv6 link-local 546 address associated with the virtual router. These fields are used 547 for troubleshooting misconfigured routers. If more than one address 548 is sent it is recommended that all routers be configured to send 549 these addresses in the same order to make it easier to do this 550 comparison. 552 6. Protocol State Machine 554 6.1 Parameters per Virtual Router 556 VRID Virtual Router Identifier. Configurable 557 item in the range 1-255 (decimal). There is 558 no default. 560 Priority Priority value to be used by this VRRP 561 router in Master election for this virtual 562 router. The value of 255 (decimal) is 563 reserved for the router that owns the IPv6 564 address associated with the virtual router. 565 The value of 0 (zero) is reserved for Master 566 router to indicate it is releasing 567 responsibility for the virtual router. The 568 range 1-254 (decimal) is available for VRRP 569 routers backing up the virtual router. The 570 default value is 100 (decimal). 572 IPv6_Addresses One or more IPv6 addresses associated with 573 this virtual router. Configured item. No 574 default. The first address must be the 575 Link-Local address associated with the 576 virtual router. 578 Advertisement_Interval Time interval between ADVERTISEMENTS 579 (centiseconds). Default is 100 centiseconds 580 (1 second). 582 Master_Adver_Interval Advertisement interval contained in 583 ADVERTISEMENTS received from the Master 584 (centiseconds). This value is saved by 585 virtual routers in Backup state and used to 586 compute Skew_Time and Master_Down_Interval. 587 The initial value is same as 588 Advertisement_Interval. 590 Skew_Time Time to skew Master_Down_Interval in 591 centiseconds. Calculated as: 593 (((256 - priority) * 594 Master_Adver_Interval) / 256). 596 Master_Down_Interval Time interval for Backup to declare Master 597 down (centiseconds). Calculated as: 599 (3 * Master_Adver_Interval) + Skew_time 601 Preempt_Mode Controls whether a higher priority Backup 602 router preempts a lower priority Master. 603 Values are True to allow preemption and 604 False to prohibit preemption. Default is 605 True. 607 Note: Exception is that the router that owns 608 the IPv6 address associated with the virtual 609 router always preempts independent of the 610 setting of this flag. 612 Accept_Mode Controls whether a virtual router in Master 613 state will accept packets addressed to the 614 address owner's IPv6 address as its own if 615 it is not the IPv6 address owner. Default 616 is False. 618 6.2 Timers 620 Master_Down_Timer Timer that fires when ADVERTISEMENT has not 621 been heard for Master_Down_Interval. 623 Adver_Timer Timer that fires to trigger sending of 624 ADVERTISEMENT based on 625 Advertisement_Interval. 627 6.3 State Transition Diagram 629 +---------------+ 630 +--------->| |<-------------+ 631 | | Initialize | | 632 | +------| |----------+ | 633 | | +---------------+ | | 634 | | | | 635 | V V | 636 +---------------+ +---------------+ 637 | |---------------------->| | 638 | Master | | Backup | 639 | |<----------------------| | 640 +---------------+ +---------------+ 642 6.4 State Descriptions 644 In the state descriptions below, the state names are identified by 645 {state-name}, and the packets are identified by all upper case 646 characters. 648 A VRRP router implements an instance of the state machine for each 649 virtual router election it is participating in. 651 6.4.1 Initialize 653 The purpose of this state is to wait for a Startup event. If a 654 Startup event is received, then: 656 - If the Priority = 255 (i.e., the router owns the IPv6 address 657 associated with the virtual router) 659 o Send an ADVERTISEMENT 660 o Send an unsolicited ND Neighbor Advertisement with the Router 661 Flag (R) set, the Solicited Flag (S) unset, the Override flag 662 (O) set, the Target Address set to the IPv6 link-local address 663 of the Virtual Router, and the Target Link Layer address set to 664 the virtual router MAC address. 665 o Set the Adver_Timer to Advertisement_Interval 666 o Transition to the {Master} state 668 else 670 o Set Master_Adver_Interval to Advertisement_Interval 671 o Set the Master_Down_Timer to Master_Down_Interval 672 o Transition to the {Backup} state 674 endif 676 6.4.2 Backup 678 The purpose of the {Backup} state is to monitor the availability and 679 state of the Master Router. 681 While in this state, a VRRP router MUST do the following: 683 - MUST NOT respond to ND Neighbor Solicitation messages for the IPv6 684 address(es) associated with the virtual router. 686 - MUST NOT send ND Router Advertisement messages for the virtual 687 router. 689 - MUST discard packets with a destination link layer MAC address 690 equal to the virtual router MAC address. 692 - MUST NOT accept packets addressed to the IPv6 address(es) 693 associated with the virtual router. 695 - If a Shutdown event is received, then: 697 o Cancel the Master_Down_Timer 698 o Transition to the {Initialize} state 700 endif 702 - If the Master_Down_Timer fires, then: 704 o Send an ADVERTISEMENT 705 o Compute and join the Solicited-Node multicast address [ADD-ARH] 706 for the IPv6 address(es) addresses associated with the the 707 Virtual Router. 708 o Send an unsolicited ND Neighbor Advertisement with the Router 709 Flag (R) set, the Solicited Flag (S) unset, the Override flag 710 (O) set, the Target Address set to the IPv6 link-local address 711 of the Virtual Router, and the Target Link Layer address set to 712 the virtual router MAC address. 713 o Set the Adver_Timer to Advertisement_Interval 714 o Transition to the {Master} state 716 endif 718 - If an ADVERTISEMENT is received, then: 720 If the Priority in the ADVERTISEMENT is Zero, then: 722 o Set the Master_Down_Timer to Skew_Time 724 else: 726 If Preempt_Mode is False, or If the Priority in the 727 ADVERTISEMENT is greater than or equal to the local 728 Priority, then: 730 o Set Master_Adver_Interval to Adver Interval contained in 731 the ADVERTISEMENT. 732 o Reset the Master_Down_Timer to Master_Down_Interval 734 else: 736 o Discard the ADVERTISEMENT 738 endif 739 endif 740 endif 742 6.4.3 Master 744 While in the {Master} state the router functions as the forwarding 745 router for the IPv6 address associated with the virtual router. 747 While in this state, a VRRP router MUST do the following: 749 - MUST be a member of the Solicited-Node multicast address for the 750 IPv6 link-local address associated with the virtual router. 752 - MUST respond to ND Neighbor Solicitation message for the IPv6 753 address(es) associated with the virtual router. 755 - MUST send ND Router Advertisements for the virtual router. 757 - MUST respond to ND Router Solicitation message for the virtual 758 router. 760 - MUST forward packets with a destination link layer MAC address 761 equal to the virtual router MAC address. 763 - MUST accept packets addressed to the IPv6 address(es) associated 764 with the virtual router if it is the IPv6 address owner or if 765 Accept_Mode is True. Otherwise, MUST NOT accept these packets. 767 - If a Shutdown event is received, then: 769 o Cancel the Adver_Timer 770 o Send an ADVERTISEMENT with Priority = 0 771 o Transition to the {Initialize} state 773 endif 775 - If the Adver_Timer fires, then: 777 o Send an ADVERTISEMENT 778 o Reset the Adver_Timer to Advertisement_Interval 780 endif 782 - If an ADVERTISEMENT is received, then: 784 If the Priority in the ADVERTISEMENT is Zero, then: 786 o Send an ADVERTISEMENT 787 o Reset the Adver_Timer to Advertisement_Interval 789 else: 791 If the Priority in the ADVERTISEMENT is greater than the 792 local Priority, 793 or 794 If the Priority in the ADVERTISEMENT is equal to the local 795 Priority and the IPv6 Address of the sender is greater than 796 the local IPv6 Address, then: 798 o Cancel Adver_Timer 799 o Set Master_Adver_Interval to Adver Interval contained in 800 the ADVERTISEMENT. 801 o Set Master_Down_Timer to Master_Down_Interval 802 o Transition to the {Backup} state 804 else: 806 o Discard ADVERTISEMENT 808 endif 809 endif 810 endif 812 7. Sending and Receiving VRRP Packets 814 7.1 Receiving VRRP Packets 816 Performed the following functions when a VRRP packet is received: 818 - MUST verify that the IPv6 Hop Limit is 255. 819 - MUST verify the VRRP version is 3 820 - MUST verify that the received packet contains the complete VRRP 821 packet (including fixed fields, and IPv6 Address. 822 - MUST verify the VRRP checksum 823 - MUST verify that the VRID is configured on the receiving 824 interface and the local router is not the IPv6 Address owner 825 (Priority equals 255 (decimal)). 827 If any one of the above checks fails, the receiver MUST discard the 828 packet, SHOULD log the event and SHOULD indicate via network 829 management that an error occurred. 831 - MAY verify that the IPv6 Address matches the IPv6_Address 832 configured for the VRID. 834 If the above check fails, the receiver SHOULD log the event and 835 SHOULD indicate via network management that a misconfiguration was 836 detected. If the packet was not generated by the address owner 837 (Priority does not equal 255 (decimal)), the receiver MUST drop the 838 packet, otherwise continue processing. 840 - MUST verify that the Adver Interval in the packet is the same as 841 the locally configured for this virtual router 843 If the above check fails, the receiver SHOULD log the event and 844 SHOULD indicate via network management that a misconfiguration was 845 detected. However, the packet is not discarded. If the virtual 846 router is in Backup state, it uses the received Adver Interval to re- 847 calculate its Master_Down_Interval. 849 7.2 Transmitting VRRP Packets 851 The following operations MUST be performed when transmitting a VRRP 852 packet. 854 - Fill in the VRRP packet fields with the appropriate virtual 855 router configuration state 856 - Compute the VRRP checksum 857 - Set the source MAC address to Virtual Router MAC Address 858 - Set the source IPv6 address to interface link-local IPv6 address 859 - Set the IPv6 protocol to VRRP 860 - Send the VRRP packet to the VRRP IP multicast group 862 Note: VRRP packets are transmitted with the virtual router MAC 863 address as the source MAC address to ensure that learning bridges 864 correctly determine the LAN segment the virtual router is attached 865 to. 867 7.3 Virtual Router MAC Address 869 The virtual router MAC address associated with a virtual router is an 870 IEEE 802 MAC Address in the following format: 872 00-00-5E-00-02-{VRID} (in hex in internet standard bit-order) 874 The first three octets are derived from the IANA's OUI. The next two 875 octets (00-02) indicate the address block assigned to the VRRP for 876 IPv6 protocol. {VRID} is the VRRP Virtual Router Identifier. This 877 mapping provides for up to 255 VRRP routers on a network. 879 7.4 IPv6 Interface Identifiers 881 IPv6 Routers running VRRP MUST create their Interface Identifiers in 882 the normal manner (e.g., RFC2464 "Transmission of IPv6 Packets over 883 Ethernet"). They MUST NOT use the Virtual Router MAC address to 884 create the Modified EUI-64 identifiers. 886 This VRRP specification describes how to advertise and resolve the 887 VRRP routers IPv6 link local address into the Virtual Router MAC 888 address. 890 8. Operational Issues 892 8.1 ICMPv6 Redirects 894 ICMPv6 Redirects may be used normally when VRRP is running between a 895 group of routers [ICMPv6]. This allows VRRP to be used in 896 environments where the topology is not symmetric (e.g., the VRRP 897 routers do not connect to the same destinations). 899 The IPv6 source address of an ICMPv6 redirect should be the address 900 the end host used when making its next hop routing decision. If a 901 VRRP router is acting as Master for virtual router(s) containing 902 addresses it does not own, then it must determine which virtual 903 router the packet was sent to when selecting the redirect source 904 address. One method to deduce the virtual router used is to examine 905 the destination MAC address in the packet that triggered the 906 redirect. 908 8.2 ND Neighbor Solicitation 910 When a host sends an ND Neighbor Solicitation message for the virtual 911 router IPv6 address, the Master virtual router MUST respond to the ND 912 Neighbor Solicitation message with the virtual MAC address for the 913 virtual router. The Master virtual router MUST NOT respond with its 914 physical MAC address. This allows the client to always use the same 915 MAC address regardless of the current Master router. 917 When a Master virtual router sends an ND Neighbor Solicitation 918 message for a host's IPv6 address, the Master virtual router MUST 919 include the virtual MAC address for the virtual router if it sends a 920 source link-layer address option in the neighbor solicitation 921 message. It MUST NOT use its physical MAC address in the source 922 link-layer address option. 924 When a VRRP router restarts or boots, it SHOULD not send any ND 925 messages with its physical MAC address for the IPv6 address it owns, 926 it should only send ND messages that include Virtual MAC addresses. 927 This may entail: 929 - When configuring an interface, VRRP routers should send an 930 unsolicitated ND Neighbor Advertisement message containing the 931 virtual router MAC address for the IPv6 address on that interface. 933 - At system boot, when initializing interfaces for VRRP operation; 934 delay all ND Router and Neighbor Advertisements and Solicitation 935 messages until both the IPv6 address and the virtual router MAC 936 address are configured. 938 8.3 Router Advertisements 940 When a backup VRRP router has become Master for a virtual router, it 941 is responsible for sending Router Advertisements for the virtual 942 router as specified in section 6.4.3. The backup routers must be 943 configured to send the same Router Advertisement options as the 944 address owner. 946 Router Advertisement options that advertise special services (e.g., 947 Home Agent Information Option) that are present in the address owner, 948 should not be sent by the address owner unless the backup routers are 949 prepared to assume these services in full and have a complete and 950 synchronized database for this service. 952 8.4 Potential Forwarding Loop 954 A VRRP router SHOULD not forward packets addressed to the IPv6 955 Address it becomes Master for if it is not the owner. Forwarding 956 these packets would result in unnecessary traffic. Also in the case 957 of LANs that receive packets they transmit (e.g., token ring) this 958 can result in a forwarding loop that is only terminated when the IPv6 959 TTL expires. 961 One such mechanism for VRRP routers is to add/delete a reject host 962 route for each adopted IPv6 address when transitioning to/from MASTER 963 state. 965 8.5 Recommendations regarding setting priority values 967 A priority value of 255 designates a particular router as the "IPv6 968 address owner". Care must be taken not to configure more than one 969 router on the link in this way for a single VRID. 971 Routers with priority 255 will, as soon as they start up, preempt all 972 lower priority routers. Configure no more than one router on the 973 link with priority 255, especially if preemption is set. If no 974 router has this priority, and preemption is disabled, then no 975 preemption will occur. 977 When there are multiple Backup routers, their priority values should 978 be uniformly distributed. For example, if one Backup routers has the 979 default priority of 100 and another BR is added, a priority of 50 980 would be a better choice for it than 99 or 100 to facilitate faster 981 convergence. 983 9. Operation over FDDI, Token Ring, and ATM LANE 985 9.1 Operation over FDDI 987 FDDI interfaces remove from the FDDI ring frames that have a source 988 MAC address matching the device's hardware address. Under some 989 conditions, such as router isolations, ring failures, protocol 990 transitions, etc., VRRP may cause there to be more than one Master 991 router. If a Master router installs the virtual router MAC address 992 as the hardware address on a FDDI device, then other Masters' 993 ADVERTISEMENTS will be removed from the ring during the Master 994 convergence, and convergence will fail. 996 To avoid this an implementation SHOULD configure the virtual router 997 MAC address by adding a unicast MAC filter in the FDDI device, rather 998 than changing its hardware MAC address. This will prevent a Master 999 router from removing any ADVERTISEMENTS it did not originate. 1001 9.2 Operation over Token Ring 1003 Token ring has several characteristics that make running VRRP 1004 difficult. These include: 1006 - In order to switch to a new master located on a different bridge 1007 token ring segment from the previous master when using source 1008 route bridges, a mechanism is required to update cached source 1009 route information. 1011 - No general multicast mechanism supported across old and new token 1012 ring adapter implementations. While many newer token ring adapters 1013 support group addresses, token ring functional address support is 1014 the only generally available multicast mechanism. Due to the 1015 limited number of token ring functional addresses these may 1016 collide with other usage of the same token ring functional 1017 addresses. 1019 Due to these difficulties, the preferred mode of operation over token 1020 ring will be to use a token ring functional address for the VRID 1021 virtual MAC address. Token ring functional addresses have the two 1022 high order bits in the first MAC address octet set to B'1'. They 1023 range from 03-00-00-00-00-80 to 03-00-02-00-00-00 (canonical format). 1024 However, unlike multicast addresses, there is only one unique 1025 functional address per bit position. The functional addresses 1026 addresses 03-00-00-10-00-00 through 03-00-02-00-00-00 are reserved 1027 by the Token Ring Architecture [TKARCH] for user-defined 1028 applications. However, since there are only 12 user-defined token 1029 ring functional addresses, there may be other non-IP protocols using 1030 the same functional address. Since the Novell IPX [IPX] protocol uses 1031 the 03-00-00-10-00-00 functional address, operation of VRRP over 1032 token ring will avoid use of this functional address. In general, 1033 token ring VRRP users will be responsible for resolution of other 1034 user-defined token ring functional address conflicts. 1036 VRIDs are mapped directly to token ring functional addresses. In 1037 order to decrease the likelihood of functional address conflicts, 1038 allocation will begin with the largest functional address. Most non- 1039 IP protocols use the first or first couple user-defined functional 1040 addresses and it is expected that VRRP users will choose VRIDs 1041 sequentially starting with 1. 1043 VRID Token Ring Functional Address 1044 ---- ----------------------------- 1045 1 03-00-02-00-00-00 1046 2 03-00-04-00-00-00 1047 3 03-00-08-00-00-00 1048 4 03-00-10-00-00-00 1049 5 03-00-20-00-00-00 1050 6 03-00-40-00-00-00 1051 7 03-00-80-00-00-00 1052 8 03-00-00-01-00-00 1053 9 03-00-00-02-00-00 1054 10 03-00-00-04-00-00 1055 11 03-00-00-08-00-00 1057 Or more succinctly, octets 3 and 4 of the functional address are 1058 equal to (0x4000 >> (VRID - 1)) in non-canonical format. 1060 Since a functional address cannot be used used as a MAC level source 1061 address, the real MAC address is used as the MAC source address in 1062 VRRP advertisements. This is not a problem for bridges since packets 1063 addressed to functional addresses will be sent on the spanning-tree 1064 explorer path [802.1D]. 1066 The functional address mode of operation MUST be implemented by 1067 routers supporting VRRP on token ring. 1069 Additionally, routers MAY support unicast mode of operation to take 1070 advantage of newer token ring adapter implementations that support 1071 non-promiscuous reception for multiple unicast MAC addresses and to 1072 avoid both the multicast traffic and usage conflicts associated with 1073 the use of token ring functional addresses. Unicast mode uses the 1074 same mapping of VRIDs to virtual MAC addresses as Ethernet. However, 1075 one important difference exists. ND request/reply packets contain the 1076 virtual MAC address as the source MAC address. The reason for this is 1077 that some token ring driver implementations keep a cache of MAC 1078 address/source routing information independent of the ND cache. 1079 Hence, these implementations need have to receive a packet with the 1080 virtual MAC address as the source address in order to transmit to 1081 that MAC address in a source-route bridged network. 1083 Unicast mode on token ring has one limitation that should be 1084 considered. If there are VRID routers on different source-route 1085 bridge segments and there are host implementations that keep their 1086 source-route information in the ND cache and do not listen to 1087 gratuitous NDs, these hosts will not update their ND source-route 1088 information correctly when a switch-over occurs. The only possible 1089 solution is to put all routers with the same VRID on the same source- 1090 bridge segment and use techniques to prevent that bridge segment from 1091 being a single point of failure. These techniques are beyond the 1092 scope this document. 1094 For both the multicast and unicast mode of operation, VRRP 1095 advertisements sent to 224.0.0.18 should be encapsulated as described 1096 in [RFC1469]. 1098 9.3 Operation over ATM LANE 1100 Operation of VRRP over ATM LANE on routers with ATM LANE interfaces 1101 and/or routers behind proxy LEC's are beyond the scope of this 1102 document. 1104 10. Security Considerations 1106 VRRP for IPv6 does not currently include any type of authentication. 1107 Earlier versions of the VRRP (for IPv4) specification included 1108 several types of authentication ranging from none to strong. 1109 Operational experience and further analysis determined that these did 1110 not provide sufficient security to overcome the vulnerability of 1111 misconfigured secrets causing multiple masters to be elected. Due to 1112 the nature of the VRRP protocol, even if VRRP messages are 1113 cryptographically protected, it does not prevent hostile routers from 1114 behaving as if they are a VRRP master, creating multiple masters. 1115 Authentication of VRRP messages could have prevented a hostile router 1116 from causing all properly functioning routers from going into backup 1117 state. However, having multiple masters can cause as much disruption 1118 as no routers, which authentication cannot prevent. Also, even if a 1119 hostile router could not disrupt VRRP, it can disrupt ARP and create 1120 the same effect as having all routers go into backup. 1122 It should be noted that these attacks are not worse and are a subset 1123 of the attacks that any node attached to a LAN can do independently 1124 of VRRP. The kind of attacks a malicious node on a LAN can do 1125 include promiscuously receiving packets for any router's MAC address, 1126 sending packets with the router's MAC address as the source MAC 1127 addresses in the L2 header to tell the L2 switches to send packets 1128 addressed to the router to the malicious node instead of the router, 1129 send redirects to tell the hosts to send their traffic somewhere 1130 else, send unsolicited ND replies, answer ND requests, etc., etc. 1131 All of this can be done independently of implementing VRRP. VRRP 1132 does not add to these vulnerabilities. 1134 Independent of any authentication type VRRP includes a mechanism 1135 (setting TTL=255, checking on receipt) that protects against VRRP 1136 packets being injected from another remote network. This limits most 1137 vulnerabilities to local attacks. 1139 VRRP does not provide any confidentiality. Confidentiality is not 1140 necessary for the correct operation of VRRP and there is no 1141 information in the VRRP messages that must be kept secret from other 1142 nodes on the LAN. 1144 If SEcure Neighbor Discovery (SEND) [SEND] is deployed, VRRP 1145 authentication could be usefully added, because misconfiguration of 1146 secrets will not be an issue. Routers with different secrets will 1147 have different IP addresses, and therefore there will be no issue 1148 with multiple masters with the same IP (and MAC) addresses. Also, 1149 SEND will prevent malicious routers from sending misleading ND 1150 messages. 1152 11. Intellectual Property 1154 The IETF takes no position regarding the validity or scope of any 1155 Intellectual Property Rights or other rights that might be claimed to 1156 pertain to the implementation or use of the technology described in 1157 this document or the extent to which any license under such rights 1158 might or might not be available; nor does it represent that it has 1159 made any independent effort to identify any such rights. Information 1160 on the procedures with respect to rights in RFC documents can be 1161 found in BCP 78 and BCP 79. 1163 Copies of IPR disclosures made to the IETF Secretariat and any 1164 assurances of licenses to be made available, or the result of an 1165 attempt made to obtain a general license or permission for the use of 1166 such proprietary rights by implementers or users of this 1167 specification can be obtained from the IETF on-line IPR repository at 1168 http://www.ietf.org/ipr. 1170 The IETF invites any interested party to bring to its attention any 1171 copyrights, patents or patent applications, or other proprietary 1172 rights that may cover technology that may be required to implement 1173 this standard. Please address the information to the IETF at 1174 ietf-ipr@ietf.org. 1176 The IETF has been notified of intellectual property rights claimed in 1177 regard to some or all of the specification contained in this 1178 document. For more information consult the online list of claimed 1179 rights. 1181 12. Acknowledgments 1183 This specification is based on RFC2238. The authors of RFC2238 are 1184 S. Knight, D. Weaver, D. Whipple, R. Hinden, D. Mitzel, P. Hunt, P. 1185 Higginson, M. Shand, and A. Lindem. 1187 The author of this document would also like to thank Erik Nordmark, 1188 Thomas Narten, Steve Deering, Radia Perlman, Danny Mitzel, Mukesh 1189 Gupta, Don Provan, Mark Hollinger, John Cruz, and Melissa Johnson for 1190 their helpful suggestions. 1192 13. IANA Considerations 1194 VRRP for IPv6 needs an IPv6 link-local scope multicast address 1195 assigned by the IANA for this specification. The IPv6 multicast 1196 address should be of the following form: 1198 FF02:0:0:0:0:0:XXXX:XXXX 1200 The values assigned address should be entered into section 5.2.2. 1202 A convenient assignment of this link-local scope multicast would be: 1204 FF02:0:0:0:0:0:0:12 1206 as this would be consistent with the IPv4 assignment for VRRP. 1208 The IANA should also reserve a block of IANA Ethernet unicast 1209 addresses from: 1211 00-00-5E-00-02-00 to 00-00-5E-00-02-FF in hex 1213 for VRRP for IPv6. Similar assignments are documented in: 1215 http://www.iana.org/assignments/ethernet-numbers 1217 14. Normative References 1219 [802.1D] International Standard ISO/IEC 10038: 1993, ANSI/IEEE Std 1220 802.1D, 1993 edition. 1222 [ADD-ARH] Hinden, R., S. Deering, "IP Version 6 Addressing 1223 Architecture", RFC4291, February 2006. 1225 [ICMPv6] Conta, A., S. Deering, M. Gupta, "Internet Control Message 1226 Protocol (ICMPv6) for the Internet Protocol Version 6 1227 (IPv6) Specification", RFC4443, March 2006. 1229 [IPv6] Deering, S., R. Hinden, "Internet Protocol, Version 6 1230 (IPv6) Specification", RFC2460, December 1998. 1232 [IPX] Novell Incorporated., "IPX Router Specification", Version 1233 1.10, October 1992. 1235 [ND] Narten, T., E. Nordmark, W. Simpson, "Neighbor Discovery 1236 for IP Version 6 (IPv6)", RFC2461, December 1998. 1238 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1239 Requirement Levels", RFC2119, BCP0014, March 1997. 1241 [SEND] Arkko, J., Kempf, J., Sommerfeld, B., Zill, B. and P. 1242 Nikander, "SEcure Neighbor Discovery (SEND)", RFC3971, 1243 March 2005. 1245 [TKARCH] IBM Token-Ring Network, Architecture Reference, Publication 1246 SC30-3374-02, Third Edition, (September, 1989). 1248 [VRRP-V4] Hinder, R., "Virtual Router Redundancy Protocol (VRRP)", 1249 RFC3768, April 2004. 1251 15. Informative References 1253 [HSRP] Li, T., B. Cole, P. Morton, D. Li, "Cisco Hot Standby 1254 Router Protocol (HSRP)", RFC2281, March 1998. 1256 [IPSTB] Higginson, P., M. Shand, "Development of Router Clusters to 1257 Provide Fast Failover in IP Networks", Digital Technical 1258 Journal, Volume 9 Number 3, Winter 1997. 1260 [CKSM] Braden, R., D. Borman, C. Partridge, "Computing the 1261 Internet Checksum", RFC1071, September 1988. 1263 [RFC1469] Pusateri, T., "IP Multicast over Token Ring Local Area 1264 Networks", RFC1469, June 1993. 1266 16. Changes from RFC2338 1268 - Added new subsection (8.3) that provided more detail on sending ND 1269 Router Advertisements. 1270 - Added new subsection (8.5) with recommendations about setting 1271 priority values and it's relationship to the preempt flag. 1272 - Changed rules for receiving VRRP packets to not drop the packet if 1273 the Adver Interval is not consistent with the local configuration 1274 for the virtual router. Only log and notify network management. 1275 Moreover, use the Master's Adver Interval to compute 1276 Master_Down_Interval and Skew_Time. 1277 - Reduced granularity of the Advertisement_Interval to centiseconds 1278 (i.e., 1/100 of a second). Changes include: 1279 o Made Adver Int field in the header 12-bits to allow range from 1280 1 to 4096 centiseconds. 1281 o Change Skew_Timer calculation to skew over one 1282 Advertisement_Interval. 1283 - Added switch (Accept_Mode) to control whether a virtual router in 1284 Master state will accept packets addresses to the address owner's 1285 IPv6 address as its own if it is not the IPv6 address owner. 1286 - Changed VMAC assignments to a separate block of IANA Ethernet 1287 addresses and added this to the IANA considerations section. 1288 - Removed different authentication methods, header fields, and 1289 updated the security considerations section to explain the reasons 1290 for doing this. 1291 - General rewrite to change protocol to provide virtual router 1292 functionality from IPv4 to IPv6. Specific changes include: 1293 o Increment VRRP version to 3. 1294 o Change packet format to support an 128-bit IPv6 address. 1295 o Rewrote text to specify IPv6 Neighbor Discovery mechanisms 1296 instead of ARP. 1297 o Changed state machine actions to use Neighbor Discovery 1298 mechanisms. This includes sending unsolicited Neighbor 1299 Advertisements, Receiving Neighbor Solicitations, joining the 1300 appropriate solicited node multicast group, sending Router 1301 Advertisements, and receiving Router Solicitations. 1302 - Revised the section 4 examples text with a clearer description of 1303 mapping of IPv6 address owner, priorities, etc. 1304 - Clarify the section 7.1 text describing address list validation. 1305 - Corrected text in Preempt_Mode definition. 1306 - Changed authentication to be per Virtual Router instead of per 1307 Interface. 1308 - Added new subsection (9.3) stating that VRRP over ATM LANE is 1309 beyond the scope of this document. 1310 - Clarified text describing received packet length check. 1312 - Clarified text describing received authentication check. 1313 - Clarified text describing VRID verification check. 1314 - Added new subsection (8.3) describing need to not forward packets 1315 for adopted IPv6 addresses. 1316 - Added clarification to the security considerations section. Added 1317 reference to SEND. 1318 - Added reference for computing the internet checksum. 1319 - Updated references and author information. 1321 Full Copyright Statement 1323 Copyright (C) The IETF Trust (2007). 1325 This document is subject to the rights, licenses and restrictions 1326 contained in BCP 78, and except as set forth therein, the authors 1327 retain all their rights. 1329 This document and the information contained herein are provided on an 1330 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS 1331 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND 1332 THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS 1333 OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF 1334 THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED 1335 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 1337 Authors' Addresses 1339 Robert Hinden 1340 Nokia, Inc. 1341 313 Fairchild Drive 1342 Mountain View, CA 94043 1343 USA 1345 Phone: +1 650 625-2004 1346 EMail: bob.hinden@nokia.com 1348 John Cruz 1349 Cisco Systems, Inc. 1350 3600 Cisco Way 1351 San Jose, CA 95134 1352 USA 1354 Phone: +1 408 527 1034 1355 Email: johcruz@cisco.com