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Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- ** The document seems to lack a 1id_guidelines paragraph about the list of current Internet-Drafts. ** The document seems to lack a 1id_guidelines paragraph about the list of Shadow Directories. == 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: ---------------------------------------------------------------------------- == Line 532 has weird spacing: '...ncluded is sp...' == 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 13, 2004) is 7371 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) == Missing Reference: 'RFC 2119' is mentioned on line 136, but not defined == Unused Reference: 'RFC2119' is defined on line 1192, but no explicit reference was found in the text == Unused Reference: 'OSPF' is defined on line 1210, but no explicit reference was found in the text == Unused Reference: 'RIP' is defined on line 1212, but no explicit reference was found in the text ** Obsolete normative reference: RFC 3513 (ref. 'ADD-ARH') (Obsoleted by RFC 4291) ** Downref: Normative reference to an Informational RFC: RFC 1071 (ref. 'CKSM') ** Obsolete normative reference: RFC 2463 (ref. 'ICMPv6') (Obsoleted by RFC 4443) ** 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) ** Downref: Normative reference to an Historic RFC: RFC 1469 -- Possible downref: Non-RFC (?) normative reference: ref. 'TKARCH' ** Obsolete normative reference: RFC 2338 (ref. 'VRRP-V4') (Obsoleted by RFC 3768) Summary: 11 errors (**), 0 flaws (~~), 10 warnings (==), 4 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 INTERNET-DRAFT R. Hinden/Nokia 3 February 13, 2004 5 Virtual Router Redundancy Protocol for IPv6 7 9 Status of this Memo 11 This document is an Internet-Draft and is in full conformance with 12 all provisions of Section 10 of [RFC2026]. 14 Internet-Drafts are working documents of the Internet Engineering 15 Task Force (IETF), its areas, and its working groups. Note that 16 other groups may also distribute working documents as Internet- 17 Drafts. 19 Internet-Drafts are draft documents valid for a maximum of six months 20 and may be updated, replaced, or obsoleted by other documents at any 21 time. It is inappropriate to use Internet-Drafts as reference 22 material or to cite them other than as "work in progress." 24 To view the list Internet-Draft Shadow Directories, see 25 http://www.ietf.org/shadow.html. 27 This internet draft expires on August 18, 2004. 29 Abstract 31 This memo defines the Virtual Router Redundancy Protocol (VRRP) for 32 IPv6. It is version three (3) of the protocol. It is based on the 33 original version of VRRP (version 2) for IPv4 that is defined in 34 RFC2338. 36 VRRP specifies an election protocol that dynamically assigns 37 responsibility for a virtual router to one of the VRRP routers on a 38 LAN. The VRRP router controlling the IP address(es) associated with 39 a virtual router is called the Master, and forwards packets sent to 40 these IP addresses. The election process provides dynamic fail over 41 in the forwarding responsibility should the Master become 42 unavailable. The advantage gained from using VRRP for IPv6 is a 43 quicker switch over to back up routers than can be obtained with 44 standard IPv6 Neighbor Discovery [ND] mechanisms. 46 Table of Contents 48 1. Introduction................................................3 49 2. Required Features...........................................5 50 3. VRRP Overview...............................................6 51 4. Sample Configurations.......................................8 52 5. Protocol...................................................10 53 5.1 VRRP Packet Format....................................10 54 5.2 IP Field Descriptions.................................11 55 5.3 VRRP Field Descriptions...............................11 56 6. Protocol State Machine....................................13 57 6.1 Parameters per Virtual Router.........................13 58 6.2 Timers................................................13 59 6.3 State Transition Diagram..............................15 60 6.4 State Descriptions....................................15 61 7. Sending and Receiving VRRP Packets........................19 62 7.1 Receiving VRRP Packets................................19 63 7.2 Transmitting Packets..................................19 64 7.3 Virtual MAC Address...................................20 65 7.4 IPv6 Interface Identifiers............................20 66 8. Operational Issues........................................21 67 8.1 ICMPv6 Redirects......................................21 68 8.2 ND Neighbor Solicitation..............................21 69 8.3 Potential Forwarding Loop.............................22 70 8.4 Recommendations regarding setting priority values.....22 71 9. Operation over FDDI, Token Ring, and ATM LANE.............22 72 9.1 Operation over FDDI...................................22 73 9.2 Operation over Token Ring.............................22 74 9.3 Operation over ATM LANE...............................25 75 10. Security Considerations...................................25 76 11. Intellectual Property.....................................26 77 12. Acknowledgments...........................................26 78 13. IANA Considerations.......................................27 79 14. Normative References......................................27 80 15. Informative References....................................28 81 16. Authors' Address..........................................28 82 17. Changes from RFC2338......................................29 84 1. Introduction 86 IPv6 hosts on a LAN will usually learn about one or more default 87 routers by receiving Router Advertisements sent using the IPv6 88 Neighbor Discovery protocol [ND]. The Router Advertisements are 89 multicast periodically at a rate that the hosts will learn about the 90 default routers in a few minutes. They are not sent frequently enough 91 to rely on the absence of the router advertisement to detect router 92 failures. 94 Neighbor Discovery (ND) includes a mechanism called Neighbor 95 Unreachability Detection to detect the failure of a neighbor node 96 (router or host) or the forwarding path to a neighbor. This is done 97 by sending unicast ND Neighbor Solicitation messages to the neighbor 98 node. To reduce the overhead of sending Neighbor Solicitations, they 99 are only sent to neighbors to which the node is actively sending 100 traffic and only after there has been no positive indication that the 101 router is up for a period of time. Using the default parameters in 102 ND, it will take a host about 38 seconds to learn that a router is 103 unreachable before it will switch to another default router. This 104 delay would be very noticeable to users and cause some transport 105 protocol implementations to timeout. 107 While the ND unreachability detection could be speeded up by changing 108 the parameters to be more aggressive (note that the current lower 109 limit for this is 5 seconds), this would have the downside of 110 significantly increasing the overhead of ND traffic. Especially when 111 there are many hosts all trying to determine the reachability of a 112 one of more routers. 114 The Virtual Router Redundancy Protocol for IPv6 provides a much 115 faster switch over to an alternate default router than can be 116 obtained using standard ND procedures. Using VRRP a backup router 117 can take over for a failed default router in around three seconds 118 (using VRRP default parameters). This is done with out any 119 interaction with the hosts and a minimum amount of VRRP traffic. 121 VRRP specifies an election protocol that dynamically assigns 122 responsibility for a virtual router to one of the VRRP routers on a 123 LAN. The VRRP router controlling the IP address(es) associated with 124 a virtual router is called the Master, and forwards packets sent to 125 these IP addresses. The election process provides dynamic fail over 126 in the forwarding responsibility should the Master become 127 unavailable. 129 VRRP provides a function similar to the proprietary protocols Hot 130 Standby Router Protocol (HSRP) [HSRP] and IP Standby Protocol 131 [IPSTB]. 133 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 134 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 135 document are to be interpreted as described in [RFC 2119]. 137 1.1 Scope 139 The remainder of this document describes the features, design goals, 140 and theory of operation of VRRP for IPv6. The message formats, 141 protocol processing rules and state machine that guarantee 142 convergence to a single Virtual Router Master are presented. 143 Finally, operational issues related to MAC address mapping, handling 144 of Neighbor Discovery requests, generation of ICMPv6 redirect 145 messages, and security issues are addressed. 147 This protocol is intended for use with IPv6 routers only. VRRP for 148 IPv4 is defined in [VRRP-V4]. 150 1.2 Definitions 152 VRRP Router A router running the Virtual Router Redundancy 153 Protocol. It may participate in one or more 154 virtual routers. 156 Virtual Router An abstract object managed by VRRP that acts 157 as a default router for hosts on a shared LAN. 158 It consists of a Virtual Router Identifier and 159 an a set of associated IPv6 address(es) across 160 a common LAN. A VRRP Router may backup one or 161 more virtual routers. 163 IPv6 Address Owner The VRRP router that has the virtual router's 164 IPv6 address(es) as real interface address. 165 This is the router that, when up, will respond 166 to packets addressed to the IPv6 address(es) 167 for ICMPv6 pings, TCP connections, etc. 169 Virtual Router Master The VRRP router that is assuming the 170 responsibility of forwarding packets sent to 171 the IPv6 address(es) associated with the 172 virtual router, and answering ND requests for 173 these IPv6 address(es). Note that if the IPv6 174 address owner is available, then it will 175 always become the Master. 177 Virtual Router Backup The set of VRRP routers available to assume 178 forwarding responsibility for a virtual router 179 should the current Master fail. 181 2.0 Required Features 183 This section outlines the set of features that were considered 184 mandatory and that guided the design of VRRP. 186 2.1 IPv6 Address Backup 188 Backup of an IPv6 address(es) is the primary function of the Virtual 189 Router Redundancy Protocol. While providing election of a Virtual 190 Router Master and the additional functionality described below, the 191 protocol should strive to: 193 - Minimize the duration of black holes. 194 - Minimize the steady state bandwidth overhead and processing 195 complexity. 196 - Function over a wide variety of multiaccess LAN technologies 197 capable of supporting IPv6 traffic. 198 - Provide for election of multiple virtual routers on a network for 199 load balancing 200 - Support of multiple logical IPv6 subnets on a single LAN segment. 202 2.2 Preferred Path Indication 204 A simple model of Master election among a set of redundant routers is 205 to treat each router with equal preference and claim victory after 206 converging to any router as Master. However, there are likely to be 207 many environments where there is a distinct preference (or range of 208 preferences) among the set of redundant routers. For example, this 209 preference may be based upon access link cost or speed, router 210 performance or reliability, or other policy considerations. The 211 protocol should allow the expression of this relative path preference 212 in an intuitive manner, and guarantee Master convergence to the most 213 preferential router currently available. 215 2.3 Minimization of Unnecessary Service Disruptions 217 Once Master election has been performed then any unnecessary 218 transitions between Master and Backup routers can result in a 219 disruption in service. The protocol should ensure after Master 220 election that no state transition is triggered by any Backup router 221 of equal or lower preference as long as the Master continues to 222 function properly. 224 Some environments may find it beneficial to avoid the state 225 transition triggered when a router becomes available that is 226 preferred over the current Master. It may be useful to support an 227 override of the immediate convergence to the preferred path. 229 2.4 Efficient Operation over Extended LANs 231 Sending IPv6 packets on a multiaccess LAN requires mapping from an 232 IPv6 address to a MAC address. The use of the virtual router MAC 233 address in an extended LAN employing learning bridges can have a 234 significant effect on the bandwidth overhead of packets sent to the 235 virtual router. If the virtual router MAC address is never used as 236 the source address in a link level frame then the station location is 237 never learned, resulting in flooding of all packets sent to the 238 virtual router. To improve the efficiency in this environment the 239 protocol should: 1) use the virtual router MAC as the source in a 240 packet sent by the Master to trigger station learning; 2) trigger a 241 message immediately after transitioning to Master to update the 242 station learning; and 3) trigger periodic messages from the Master to 243 maintain the station learning cache. 245 3.0 VRRP Overview 247 VRRP specifies an election protocol to provide the virtual router 248 function described earlier. All protocol messaging is performed 249 using IPv6 multicast datagrams, thus the protocol can operate over a 250 variety of multiaccess LAN technologies supporting IPv6 multicast. 251 Each VRRP virtual router has a single well-known MAC address 252 allocated to it. This document currently only details the mapping to 253 networks using the IEEE 802 48-bit MAC address. The virtual router 254 MAC address is used as the source in all periodic VRRP messages sent 255 by the Master router to enable bridge learning in an extended LAN. 257 A virtual router is defined by its virtual router identifier (VRID) 258 and a set of IPv6 address(es). A VRRP router may associate a virtual 259 router with its real address on an interface, and may also be 260 configured with additional virtual router mappings and priority for 261 virtual routers it is willing to backup. The mapping between VRID 262 and its IPv6 address(es) must be coordinated among all VRRP routers 263 on a LAN. However, there is no restriction against reusing a VRID 264 with a different address mapping on different LANs. The scope of 265 each virtual router is restricted to a single LAN. 267 To minimize network traffic, only the Master for each virtual router 268 sends periodic VRRP Advertisement messages. A Backup router will not 269 attempt to preempt the Master unless it has higher priority. This 270 eliminates service disruption unless a more preferred path becomes 271 available. It's also possible to administratively prohibit all 272 preemption attempts. The only exception is that a VRRP router will 273 always become Master of any virtual router associated with address it 274 owns. If the Master becomes unavailable then the highest priority 275 Backup will transition to Master after a short delay, providing a 276 controlled transition of the virtual router responsibility with 277 minimal service interruption. 279 The VRRP protocol design provides rapid transition from Backup to 280 Master to minimize service interruption, and incorporates 281 optimizations that reduce protocol complexity while guaranteeing 282 controlled Master transition for typical operational scenarios. The 283 optimizations result in an election protocol with minimal runtime 284 state requirements, minimal active protocol states, and a single 285 message type and sender. The typical operational scenarios are 286 defined to be two redundant routers and/or distinct path preferences 287 among each router. A side effect when these assumptions are violated 288 (i.e., more than two redundant paths all with equal preference) is 289 that duplicate packets may be forwarded for a brief period during 290 Master election. However, the typical scenario assumptions are 291 likely to cover the vast majority of deployments, loss of the Master 292 router is infrequent, and the expected duration in Master election 293 convergence is quite small ( << 1 second ). Thus the VRRP 294 optimizations represent significant simplifications in the protocol 295 design while incurring an insignificant probability of brief network 296 degradation. 298 4. Sample Configurations 300 4.1 Sample Configuration 1 302 The following figure shows a simple network with two VRRP routers 303 implementing one virtual router. Note that this example is provided 304 to help understand the protocol, but is not expected to occur in 305 actual practice. 307 +-----------+ +-----------+ 308 | Rtr1 | | Rtr2 | 309 |(MR VRID=1)| |(BR VRID=1)| 310 | | | | 311 VRID=1 +-----------+ +-----------+ 312 IPv6 A -------->* *<--------- IPv6 B 313 | | 314 | | 315 ------------------+------------+-----+--------+--------+--------+-- 316 ^ ^ ^ ^ 317 | | | | 318 (IPv6 A) (IPv6 A) (IPv6 A) (IPv6 A) 319 | | | | 320 +--+--+ +--+--+ +--+--+ +--+--+ 321 | H1 | | H2 | | H3 | | H4 | 322 +-----+ +-----+ +--+--+ +--+--+ 323 Legend: 324 ---+---+---+-- = Ethernet, Token Ring, or FDDI 325 H = Host computer 326 MR = Master Router 327 BR = Backup Router 328 * = IPv6 Address 329 (IPv6) = default router for hosts 331 Eliminating all mention of VRRP (VRID=1) from the figure above leaves 332 it as a typical IPv6 deployment. Each router has a link-local IPv6 333 address on the LAN interface (Rtr1 is assigned IPv6 Link-Local A and 334 Rtr2 is assigned IPv6 Link-Local B), and each host learns a default 335 route from Router Advertisements through one of the routers (in this 336 example they all use Rtr1's IPv6 Link-Local A). 338 Moving to the VRRP environment, each router has the exact same Link- 339 Local IPv6 address. Rtr1 is said to be the IPv6 address owner of 340 IPv6 A, and Rtr2 is the IPv6 address owner of IPv6 B. A virtual 341 router is then defined by associating a unique identifier (the 342 virtual router ID) with the address owned by a router. Finally, the 343 VRRP protocol manages virtual router fail over to a backup router. 345 The example above shows a virtual router configured to cover the IPv6 346 address owned by Rtr1 (VRID=1,IPv6_Address=A). When VRRP is enabled 347 on Rtr1 for VRID=1 it will assert itself as Master, with 348 priority=255, since it is the IPv6 address owner for the virtual 349 router IPv6 address. When VRRP is enabled on Rtr2 for VRID=1 it will 350 transition to Backup, with priority=100, since it is not the IPv6 351 address owner. If Rtr1 should fail then the VRRP protocol will 352 transition Rtr2 to Master, temporarily taking over forwarding 353 responsibility for IPv6 A to provide uninterrupted service to the 354 hosts. 356 Note that in this example IPv6 B is not backed up, it is only used by 357 Rtr2 as its interface address. In order to backup IPv6 B, a second 358 virtual router must be configured. This is shown in the next 359 section. 361 4.2 Sample Configuration 2 363 The following figure shows a configuration with two virtual routers 364 with the hosts splitting their traffic between them. This example is 365 expected to be common in actual practice. 367 +-----------+ +-----------+ 368 | Rtr1 | | Rtr2 | 369 |(MR VRID=1)| |(BR VRID=1)| 370 |(BR VRID=2)| |(MR VRID=2)| 371 VRID=1 +-----------+ +-----------+ VRID=2 372 IPv6 A -------->* *<---------- IPv6 B 373 | | 374 | | 375 ------------------+------------+-----+--------+--------+--------+-- 376 ^ ^ ^ ^ 377 | | | | 378 (IPv6 A) (IPv6 A) (IPv6 B) (IPv6 B) 379 | | | | 380 +--+--+ +--+--+ +--+--+ +--+--+ 381 | H1 | | H2 | | H3 | | H4 | 382 +-----+ +-----+ +--+--+ +--+--+ 383 Legend: 384 ---+---+---+-- = Ethernet, Token Ring, or FDDI 385 H = Host computer 386 MR = Master Router 387 BR = Backup Router 388 * = IPv6 Address 389 (IPv6) = default router for hosts 391 In the example above, half of the hosts have learned a default route 392 through Rtr1's IPv6 A and half are using Rtr2's IPv6 B. The 393 configuration of virtual router VRID=1 is exactly the same as in the 394 first example (see section 4.1), and a second virtual router has been 395 added to cover the IPv6 address owned by Rtr2 (VRID=2, 396 IPv6_Address=B). In this case Rtr2 will assert itself as Master for 397 VRID=2 while Rtr1 will act as a backup. This scenario demonstrates a 398 deployment providing load splitting when both routers are available 399 while providing full redundancy for robustness. 401 5.0 Protocol 403 The purpose of the VRRP packet is to communicate to all VRRP routers 404 the priority and the state of the Master router associated with the 405 Virtual Router ID. 407 VRRP packets are sent encapsulated in IPv6 packets. They are sent to 408 the IPv6 multicast address assigned to VRRP. 410 5.1 VRRP Packet Format 412 This section defines the format of the VRRP packet and the relevant 413 fields in the IPv6 header. 415 0 1 2 3 416 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 1 417 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 418 |Version| Type | Virtual Rtr ID| Priority |Count IPv6 Addr| 419 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 420 |(rsvd) | Adver Int | Checksum | 421 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 422 | | 423 + + 424 | IPv6 Address(es) | 425 + + 426 + + 427 + + 428 + + 429 | | 430 + + 431 | | 432 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 434 5.2 IPv6 Field Descriptions 436 5.2.1 Source Address 438 The IPv6 link-local address of the interface the packet is being sent 439 from. 441 5.2.2 Destination Address 443 The IPv6 multicast address as assigned by the IANA for VRRP is: 445 FF02:0:0:0:0:0:XXXX:XXXX 447 This is a link-local scope multicast address. Routers MUST NOT 448 forward a datagram with this destination address regardless of its 449 Hop Limit. 451 5.2.3 Hop Limit 453 The Hop Limit MUST be set to 255. A VRRP router receiving a packet 454 with the Hop Limit not equal to 255 MUST discard the packet. 456 5.2.4 Next Header 458 The IPv6 Next Header protocol assigned by the IANA for VRRP is 112 459 (decimal). 461 5.3 VRRP Field Descriptions 463 5.3.1 Version 465 The version field specifies the VRRP protocol version of this packet. 466 This document defines version 3. 468 5.3.2 Type 470 The type field specifies the type of this VRRP packet. The only 471 packet type defined in this version of the protocol is: 473 1 ADVERTISEMENT 475 A packet with unknown type MUST be discarded. 477 5.3.3 Virtual Rtr ID (VRID) 479 The Virtual Router Identifier (VRID) field identifies the virtual 480 router this packet is reporting status for. 482 5.3.4 Priority 484 The priority field specifies the sending VRRP router's priority for 485 the virtual router. Higher values equal higher priority. This field 486 is an 8 bit unsigned integer field. 488 The priority value for the VRRP router that owns the IPv6 address 489 associated with the virtual router MUST be 255 (decimal). 491 VRRP routers backing up a virtual router MUST use priority values 492 between 1-254 (decimal). The default priority value for VRRP routers 493 backing up a virtual router is 100 (decimal). 495 The priority value zero (0) has special meaning indicating that the 496 current Master has stopped participating in VRRP. This is used to 497 trigger Backup routers to quickly transition to Master without having 498 to wait for the current Master to timeout. 500 5.3.5 Count IPv6 Addr 502 The number of IPv6 addresses contained in this VRRP advertisement. 503 The minimum value is 1. 505 5.3.5 Rsvd 507 This field MUST be set to zero on transmission and ignored on 508 reception. 510 5.3.6 Advertisement Interval (Adver Int) 512 The Advertisement interval is a 12-bit field that indicates the time 513 interval (in centiseconds) between ADVERTISEMENTS. The default is 514 100 centiseconds (1 second). This field is used for troubleshooting 515 misconfigured routers. 517 5.3.7 Checksum 519 The checksum field is used to detect data corruption in the VRRP 520 message. 522 The checksum is the 16-bit one's complement of the one's complement 523 sum of the entire VRRP message starting with the version field and a 524 "pseudo-header" as defined in section 8.1 of RFC2460 [IPv6]. The 525 next header field in the "pseudo-header" should be set to 112 526 (decimal) for VRRP. For computing the checksum, the checksum field 527 is set to zero. See RFC1071 for more detail [CKSM]. 529 5.3.8 IPv6 Address(es) 531 One or more IPv6 addresses associated associated with the virtual 532 router. The number of addresses included is specified in the "Count 533 IP Addr" field. The first address must be the IPv6 link-local 534 address associated with the virtual router. These fields are used 535 for troubleshooting misconfigured routers. 537 6. Protocol State Machine 539 6.1 Parameters per Virtual Router 541 VRID Virtual Router Identifier. Configurable 542 item in the range 1-255 (decimal). There is 543 no default. 545 Priority Priority value to be used by this VRRP 546 router in Master election for this virtual 547 router. The value of 255 (decimal) is 548 reserved for the router that owns the IPv6 549 address associated with the virtual router. 550 The value of 0 (zero) is reserved for Master 551 router to indicate it is releasing 552 responsibility for the virtual router. The 553 range 1-254 (decimal) is available for VRRP 554 routers backing up the virtual router. The 555 default value is 100 (decimal). 557 IPv6_Addresses One or more IPv6 addresses associated with 558 this virtual router. Configured item. No 559 default. The first address must be the 560 Link-Local address associated with the 561 virtual router. 563 Advertisement_Interval Time interval between ADVERTISEMENTS 564 (centiseconds). Default is 100 centiseconds 565 (1 second). 567 Skew_Time Time to skew Master_Down_Interval in 568 centiseconds. Calculated as: 570 (((256 - Priority) / 256) * 571 Advertisement_Interval) 573 Master_Down_Interval Time interval for Backup to declare Master 574 down (centiseconds). Calculated as: 576 (3 * Advertisement_Interval) + Skew_time 578 Preempt_Mode Controls whether a higher priority Backup 579 router preempts a lower priority Master. 580 Values are True to allow preemption and 581 False to prohibit preemption. Default is 582 True. 584 Note: Exception is that the router that owns 585 the IPv6 address associated with the virtual 586 router always preempts independent of the 587 setting of this flag. 589 Accept_Mode Controls whether a virtual router in Master 590 state will accept packets addressed to the 591 address owner's IPv6 address as its own if 592 it is not the IPv6 address owner. Default 593 is False. 595 6.2 Timers 597 Master_Down_Timer Timer that fires when ADVERTISEMENT has not 598 been heard for Master_Down_Interval. 600 Adver_Timer Timer that fires to trigger sending of 601 ADVERTISEMENT based on 602 Advertisement_Interval. 604 6.3 State Transition Diagram 606 +---------------+ 607 +--------->| |<-------------+ 608 | | Initialize | | 609 | +------| |----------+ | 610 | | +---------------+ | | 611 | | | | 612 | V V | 613 +---------------+ +---------------+ 614 | |---------------------->| | 615 | Master | | Backup | 616 | |<----------------------| | 617 +---------------+ +---------------+ 619 6.4 State Descriptions 621 In the state descriptions below, the state names are identified by 622 {state-name}, and the packets are identified by all upper case 623 characters. 625 A VRRP router implements an instance of the state machine for each 626 virtual router election it is participating in. 628 6.4.1 Initialize 630 The purpose of this state is to wait for a Startup event. If a 631 Startup event is received, then: 633 - If the Priority = 255 (i.e., the router owns the IPv6 address 634 associated with the virtual router) 636 o Send an ADVERTISEMENT 637 o Send an unsolicited ND Neighbor Advertisement with the Router 638 Flag (R) set, the Solicited Flag (S) unset, the Override flag 639 (O) set, the Target Address set to the IPv6 link-local address 640 of the Virtual Router, and the Target Link Layer address set to 641 the virtual router MAC address. 642 o Set the Adver_Timer to Advertisement_Interval 643 o Transition to the {Master} state 645 else 647 o Set the Master_Down_Timer to Master_Down_Interval 648 o Transition to the {Backup} state 650 endif 652 6.4.2 Backup 654 The purpose of the {Backup} state is to monitor the availability and 655 state of the Master Router. 657 While in this state, a VRRP router MUST do the following: 659 - MUST NOT respond to ND Neighbor Solicitation messages for the IPv6 660 address(es) associated with the virtual router. 662 - MUST NOT send ND Router Advertisement messages for the virtual 663 router. 665 - MUST discard packets with a destination link layer MAC address 666 equal to the virtual router MAC address. 668 - MUST NOT accept packets addressed to the IPv6 address(es) 669 associated with the virtual router. 671 - If a Shutdown event is received, then: 673 o Cancel the Master_Down_Timer 674 o Transition to the {Initialize} state 676 endif 678 - If the Master_Down_Timer fires, then: 680 o Send an ADVERTISEMENT 681 o Compute and join the Solicited-Node multicast address [ADD-ARH] 682 for the IPv6 address(es) addresses associated with the the 683 Virtual Router. 684 o Send an unsolicited ND Neighbor Advertisement with the Router 685 Flag (R) set, the Solicited Flag (S) unset, the Override flag 686 (O) set, the Target Address set to the IPv6 link-local address 687 of the Virtual Router, and the Target Link Layer address set to 688 the virtual router MAC address. 689 o Set the Adver_Timer to Advertisement_Interval 690 o Transition to the {Master} state 692 endif 694 - If an ADVERTISEMENT is received, then: 696 If the Priority in the ADVERTISEMENT is Zero, then: 698 o Set the Master_Down_Timer to Skew_Time 700 else: 702 If Preempt_Mode is False, or If the Priority in the 703 ADVERTISEMENT is greater than or equal to the local 704 Priority, then: 706 o Reset the Master_Down_Timer to Master_Down_Interval 708 else: 710 o Discard the ADVERTISEMENT 712 endif 713 endif 714 endif 716 6.4.3 Master 718 While in the {Master} state the router functions as the forwarding 719 router for the IPv6 address associated with the virtual router. 721 While in this state, a VRRP router MUST do the following: 723 - MUST be a member of the Solicited-Node multicast address for the 724 IPv6 link-local address associated with the virtual router. 726 - MUST respond to ND Neighbor Solicitation message for the IPv6 727 address(es) associated with the virtual router. 729 - MUST send ND Router Advertisements for the virtual router. 731 - MUST respond to ND Router Solicitation message for the virtual 732 router. 734 - MUST forward packets with a destination link layer MAC address 735 equal to the virtual router MAC address. 737 - MUST accept packets addressed to the IPv6 address(es) associated 738 with the virtual router if it is the IPv6 address owner or if 739 Accept_Mode is True. Otherwise, MUST NOT accept these packets. 741 - If a Shutdown event is received, then: 743 o Cancel the Adver_Timer 744 o Send an ADVERTISEMENT with Priority = 0 745 o Transition to the {Initialize} state 747 endif 749 - If the Adver_Timer fires, then: 751 o Send an ADVERTISEMENT 752 o Reset the Adver_Timer to Advertisement_Interval 754 endif 756 - If an ADVERTISEMENT is received, then: 758 If the Priority in the ADVERTISEMENT is Zero, then: 760 o Send an ADVERTISEMENT 761 o Reset the Adver_Timer to Advertisement_Interval 763 else: 765 If the Priority in the ADVERTISEMENT is greater than the 766 local Priority, 767 or 768 If the Priority in the ADVERTISEMENT is equal to the local 769 Priority and the IPv6 Address of the sender is greater than 770 the local IPv6 Address, then: 772 o Cancel Adver_Timer 773 o Set Master_Down_Timer to Master_Down_Interval 774 o Transition to the {Backup} state 776 else: 778 o Discard ADVERTISEMENT 780 endif 781 endif 782 endif 784 7. Sending and Receiving VRRP Packets 786 7.1 Receiving VRRP Packets 788 Performed the following functions when a VRRP packet is received: 790 - MUST verify that the IPv6 Hop Limit is 255. 791 - MUST verify the VRRP version is 3 792 - MUST verify that the received packet contains the complete VRRP 793 packet (including fixed fields, and IPv6 Address. 794 - MUST verify the VRRP checksum 795 - MUST verify that the VRID is configured on the receiving 796 interface and the local router is not the IPv6 Address owner 797 (Priority equals 255 (decimal)). 799 If any one of the above checks fails, the receiver MUST discard the 800 packet, SHOULD log the event and SHOULD indicate via network 801 management that an error occurred. 803 - MAY verify that the IPv6 Address matches the IPv6_Address 804 configured for the VRID. 806 If the above check fails, the receiver SHOULD log the event and 807 SHOULD indicate via network management that a misconfiguration was 808 detected. If the packet was not generated by the address owner 809 (Priority does not equal 255 (decimal)), the receiver MUST drop the 810 packet, otherwise continue processing. 812 - MUST verify that the Adver Interval in the packet is the same as 813 the locally configured for this virtual router 815 If the above check fails, the receiver SHOULD log the event and 816 SHOULD indicate via network management that a misconfiguration was 817 detected. 819 7.2 Transmitting VRRP Packets 821 The following operations MUST be performed when transmitting a VRRP 822 packet. 824 - Fill in the VRRP packet fields with the appropriate virtual 825 router configuration state 826 - Compute the VRRP checksum 827 - Set the source MAC address to Virtual Router MAC Address 828 - Set the source IPv6 address to interface link-local IPv6 address 829 - Set the IPv6 protocol to VRRP 830 - Send the VRRP packet to the VRRP IP multicast group 832 Note: VRRP packets are transmitted with the virtual router MAC 833 address as the source MAC address to ensure that learning bridges 834 correctly determine the LAN segment the virtual router is attached 835 to. 837 7.3 Virtual Router MAC Address 839 The virtual router MAC address associated with a virtual router is an 840 IEEE 802 MAC Address in the following format: 842 00-00-5E-00-02-{VRID} (in hex in internet standard bit-order) 844 The first three octets are derived from the IANA's OUI. The next two 845 octets (00-02) indicate the address block assigned to the VRRP for 846 IPv6 protocol. {VRID} is the VRRP Virtual Router Identifier. This 847 mapping provides for up to 255 VRRP routers on a network. 849 7.4 IPv6 Interface Identifiers 851 IPv6 Routers running VRRP MUST create their Interface Identifiers in 852 the normal manner (e.g., RFC2464 "Transmission of IPv6 Packets over 853 Ethernet"). They MUST NOT use the Virtual Router MAC address to 854 create the Modified EUI-64 identifiers. 856 This VRRP specification describes how to advertise and resolve the 857 VRRP routers IPv6 link local address into the Virtual Router MAC 858 address. 860 8. Operational Issues 862 8.1 ICMPv6 Redirects 864 ICMPv6 Redirects may be used normally when VRRP is running between a 865 group of routers [ICMPv6]. This allows VRRP to be used in 866 environments where the topology is not symmetric (e.g., the VRRP 867 routers do not connect to the same destinations). 869 The IPv6 source address of an ICMPv6 redirect should be the address 870 the end host used when making its next hop routing decision. If a 871 VRRP router is acting as Master for virtual router(s) containing 872 addresses it does not own, then it must determine which virtual 873 router the packet was sent to when selecting the redirect source 874 address. One method to deduce the virtual router used is to examine 875 the destination MAC address in the packet that triggered the 876 redirect. 878 8.2 ND Neighbor Solicitation 880 When a host sends an ND Neighbor Solicitation message for the virtual 881 router IPv6 address, the Master virtual router MUST respond to the ND 882 Neighbor Solicitation message with the virtual MAC address for the 883 virtual router. The Master virtual router MUST NOT respond with its 884 physical MAC address. This allows the client to always use the same 885 MAC address regardless of the current Master router. 887 When a Master virtual router sends an ND Neighbor Solicitation 888 message for a host's IPv6 address, the Master virtual router MUST 889 include the virtual MAC address for the virtual router if it sends a 890 source link-layer address option in the neighbor solicitation 891 message. It MUST NOT use its physical MAC address in the source 892 link-layer address option. 894 When a VRRP router restarts or boots, it SHOULD not send any ND 895 messages with its physical MAC address for the IPv6 address it owns, 896 it should only send ND messages that include Virtual MAC addresses. 897 This may entail: 899 - When configuring an interface, VRRP routers should send an 900 unsolicitated ND Neighbor Advertisement message containing the 901 virtual router MAC address for the IPv6 address on that interface. 903 - At system boot, when initializing interfaces for VRRP operation; 904 delay all ND Router and Neighbor Advertisements and Solicitation 905 messages until both the IPv6 address and the virtual router MAC 906 address are configured. 908 8.3 Potential Forwarding Loop 910 A VRRP router SHOULD not forward packets addressed to the IPv6 911 Address it becomes Master for if it is not the owner. Forwarding 912 these packets would result in unnecessary traffic. Also in the case 913 of LANs that receive packets they transmit (e.g., token ring) this 914 can result in a forwarding loop that is only terminated when the IPv6 915 TTL expires. 917 One such mechanism for VRRP routers is to add/delete a reject host 918 route for each adopted IPv6 address when transitioning to/from MASTER 919 state. 921 8.4 Recommendations regarding setting priority values 923 A priority value of 255 designates a particular router as the "IPv6 924 address owner". Care must be taken not to configure more than one 925 router on the link in this way for a single VRID. 927 Routers with priority 255 will, as soon as they start up, preempt all 928 lower priority routers. Configure no more than one router on the 929 link with priority 255, especially if preemption is set. If no 930 router has this priority, and preemption is disabled, then no 931 preemption will occur. 933 When there are multiple Backup routers, their priority values should 934 be uniformly distributed. For example, if one Backup routers has the 935 default priority of 100 and another BR is added, a priority of 50 936 would be a better choice for it than 99 or 100 to facilitate faster 937 convergence. 939 9. Operation over FDDI, Token Ring, and ATM LANE 941 9.1 Operation over FDDI 943 FDDI interfaces remove from the FDDI ring frames that have a source 944 MAC address matching the device's hardware address. Under some 945 conditions, such as router isolations, ring failures, protocol 946 transitions, etc., VRRP may cause there to be more than one Master 947 router. If a Master router installs the virtual router MAC address 948 as the hardware address on a FDDI device, then other Masters' 949 ADVERTISEMENTS will be removed from the ring during the Master 950 convergence, and convergence will fail. 952 To avoid this an implementation SHOULD configure the virtual router 953 MAC address by adding a unicast MAC filter in the FDDI device, rather 954 than changing its hardware MAC address. This will prevent a Master 955 router from removing any ADVERTISEMENTS it did not originate. 957 9.2 Operation over Token Ring 959 Token ring has several characteristics that make running VRRP 960 difficult. These include: 962 - In order to switch to a new master located on a different bridge 963 token ring segment from the previous master when using source 964 route bridges, a mechanism is required to update cached source 965 route information. 967 - No general multicast mechanism supported across old and new token 968 ring adapter implementations. While many newer token ring adapters 969 support group addresses, token ring functional address support is 970 the only generally available multicast mechanism. Due to the 971 limited number of token ring functional addresses these may 972 collide with other usage of the same token ring functional 973 addresses. 975 Due to these difficulties, the preferred mode of operation over token 976 ring will be to use a token ring functional address for the VRID 977 virtual MAC address. Token ring functional addresses have the two 978 high order bits in the first MAC address octet set to B'1'. They 979 range from 03-00-00-00-00-80 to 03-00-02-00-00-00 (canonical format). 980 However, unlike multicast addresses, there is only one unique 981 functional address per bit position. The functional addresses 982 addresses 03-00-00-10-00-00 through 03-00-02-00-00-00 are reserved 983 by the Token Ring Architecture [TKARCH] for user-defined 984 applications. However, since there are only 12 user-defined token 985 ring functional addresses, there may be other non-IP protocols using 986 the same functional address. Since the Novell IPX [IPX] protocol uses 987 the 03-00-00-10-00-00 functional address, operation of VRRP over 988 token ring will avoid use of this functional address. In general, 989 token ring VRRP users will be responsible for resolution of other 990 user-defined token ring functional address conflicts. 992 VRIDs are mapped directly to token ring functional addresses. In 993 order to decrease the likelihood of functional address conflicts, 994 allocation will begin with the largest functional address. Most non- 995 IP protocols use the first or first couple user-defined functional 996 addresses and it is expected that VRRP users will choose VRIDs 997 sequentially starting with 1. 999 VRID Token Ring Functional Address 1000 ---- ----------------------------- 1001 1 03-00-02-00-00-00 1002 2 03-00-04-00-00-00 1003 3 03-00-08-00-00-00 1004 4 03-00-10-00-00-00 1005 5 03-00-20-00-00-00 1006 6 03-00-40-00-00-00 1007 7 03-00-80-00-00-00 1008 8 03-00-00-01-00-00 1009 9 03-00-00-02-00-00 1010 10 03-00-00-04-00-00 1011 11 03-00-00-08-00-00 1013 Or more succinctly, octets 3 and 4 of the functional address are 1014 equal to (0x4000 >> (VRID - 1)) in non-canonical format. 1016 Since a functional address cannot be used used as a MAC level source 1017 address, the real MAC address is used as the MAC source address in 1018 VRRP advertisements. This is not a problem for bridges since packets 1019 addressed to functional addresses will be sent on the spanning-tree 1020 explorer path [802.1D]. 1022 The functional address mode of operation MUST be implemented by 1023 routers supporting VRRP on token ring. 1025 Additionally, routers MAY support unicast mode of operation to take 1026 advantage of newer token ring adapter implementations that support 1027 non-promiscuous reception for multiple unicast MAC addresses and to 1028 avoid both the multicast traffic and usage conflicts associated with 1029 the use of token ring functional addresses. Unicast mode uses the 1030 same mapping of VRIDs to virtual MAC addresses as Ethernet. However, 1031 one important difference exists. ND request/reply packets contain the 1032 virtual MAC address as the source MAC address. The reason for this is 1033 that some token ring driver implementations keep a cache of MAC 1034 address/source routing information independent of the ND cache. 1035 Hence, these implementations need have to receive a packet with the 1036 virtual MAC address as the source address in order to transmit to 1037 that MAC address in a source-route bridged network. 1039 Unicast mode on token ring has one limitation that should be 1040 considered. If there are VRID routers on different source-route 1041 bridge segments and there are host implementations that keep their 1042 source-route information in the ND cache and do not listen to 1043 gratuitous NDs, these hosts will not update their ND source-route 1044 information correctly when a switch-over occurs. The only possible 1045 solution is to put all routers with the same VRID on the same source- 1046 bridge segment and use techniques to prevent that bridge segment from 1047 being a single point of failure. These techniques are beyond the 1048 scope this document. 1050 For both the multicast and unicast mode of operation, VRRP 1051 advertisements sent to 224.0.0.18 should be encapsulated as described 1052 in [RFC1469]. 1054 9.3 Operation over ATM LANE 1056 Operation of VRRP over ATM LANE on routers with ATM LANE interfaces 1057 and/or routers behind proxy LEC's are beyond the scope of this 1058 document. 1060 10. Security Considerations 1062 VRRP for IPv6 does not currently include any type of authentication. 1063 Earlier versions of the VRRP (for IPv4) specification included 1064 several types of authentication ranging from none to strong. 1065 Operational experience and further analysis determined that these did 1066 not provide any real measure of security. Due to the nature of the 1067 VRRP protocol, even if VRRP messages are cryptographically protected, 1068 it does not prevent hostile routers from behaving as if they are a 1069 VRRP master, creating multiple masters. Authentication of VRRP 1070 messages could have prevented a hostile router from causing all 1071 properly functioning routers from going into backup state. However, 1072 having multiple masters can cause as much disruption as no routers, 1073 which authentication cannot prevent. Also, even if a hostile router 1074 could not disrupt VRRP, it can disrupt ARP and create the same effect 1075 as having all routers go into backup. 1077 It should be noted that these attacks are not worse and are a subset 1078 of the attacks that any node attached to a LAN can do independently 1079 of VRRP. The kind of attacks a malicious node on a LAN can do 1080 include promiscuously receiving packets for any routers MAC address, 1081 sending packets with the routers MAC address as the source MAC 1082 addresses in the L2 header to tell the L2 switches to send packets 1083 addressed to the router to the malicious node instead of the router, 1084 send redirects to tell the hosts to send their traffic somewhere 1085 else, send unsolicited ND replies, answer ND requests, etc., etc. 1086 All of this can be done independently of implementing VRRP. VRRP 1087 does not add to these vulnerabilities. 1089 Independent of any authentication type VRRP includes a mechanism 1090 (setting TTL=255, checking on receipt) that protects against VRRP 1091 packets being injected from another remote network. This limits most 1092 vulnerabilities to local attacks. 1094 VRRP does not provide any confidentiality. Confidentiality is not 1095 necessary for the correct operation of VRRP and there is no 1096 information in the VRRP messages that must be kept secret from other 1097 nodes on the LAN. 1099 11. Intellectual Property 1101 The IETF takes no position regarding the validity or scope of any 1102 intellectual property or other rights that might be claimed to 1103 pertain to the implementation or use of the technology described in 1104 this document or the extent to which any license under such rights 1105 might or might not be available; neither does it represent that it 1106 has made any effort to identify any such rights. Information on the 1107 IETF's procedures with respect to rights in standards-track and 1108 standards-related documentation can be found in BCP-11. Copies of 1109 claims of rights made available for publication and any assurances of 1110 licenses to be made available, or the result of an attempt made to 1111 obtain a general license or permission for the use of such 1112 proprietary rights by implementors or users of this specification can 1113 be obtained from the IETF Secretariat. See the IETF IPR web page at 1114 http://www.ietf.org/ipr.html for additional information. 1116 The IETF invites any interested party to bring to its attention any 1117 copyrights, patents or patent applications, or other proprietary 1118 rights which may cover technology that may be required to practice 1119 this standard. Please address the information to the IETF Executive 1120 Director. 1122 The IETF has been notified of intellectual property rights claimed in 1123 regard to some or all of the specification contained in this 1124 document. For more information consult the online list of claimed 1125 rights. 1127 12. Acknowledgments 1129 This specification is based on RFC2238. The authors of RFC2238 are 1130 S. Knight, D. Weaver, D. Whipple, R. Hinden, D. Mitzel, P. Hunt, P. 1131 Higginson, M. Shand, and A. Lindem. 1133 The author of this document would also like to thank Erik Nordmark, 1134 Thomas Narten, Steve Deering, Radia Perlman, Danny Mitzel, Mukesh 1135 Gupta, Don Provan, and Mark Hollinger for their helpful suggestions. 1137 13. IANA Considerations 1139 VRRP for IPv6 needs an IPv6 link-local scope multicast address 1140 assigned by the IANA for this specification. The IPv6 multicast 1141 address should be of the following form: 1143 FF02:0:0:0:0:0:XXXX:XXXX 1145 The values assigned address should be entered into section 5.2.2. 1147 A convenient assignment of this link-local scope multicast would be: 1149 FF02:0:0:0:0:0:0:12 1151 as this would be consistent with the IPv4 assignment for VRRP. 1153 The IANA should also reserve a block of IANA Ethernet unicast 1154 addresses from: 1156 00-00-5E-00-02-00 to 00-00-5E-00-02-FF in hex 1158 for VRRP for IPv6. Similar assignments are documented in: 1160 http://www.iana.org/assignments/ethernet-numbers 1162 14. Normative References 1164 [802.1D] International Standard ISO/IEC 10038: 1993, ANSI/IEEE Std 1165 802.1D, 1993 edition. 1167 [ADD-ARH] Hinden, R., S. Deering, "IP Version 6 Addressing 1168 Architecture", RFC3513, April 2003. 1170 [CKSM] Braden, R., D. Borman, C. Partridge, "Computing the 1171 Internet Checksum", RFC1071, September 1988. 1173 [ICMPv6] Conta, A., S. Deering, "Internet Control Message Protocol 1174 (ICMPv6) for the Internet Protocol Version 6 (IPv6)", 1175 RFC2463, December 1998. 1177 [IPv6] Deering, S., R. Hinden, "Internet Protocol, Version 6 1178 (IPv6) Specification", RFC2460, December 1998. 1180 [IPX] Novell Incorporated., "IPX Router Specification", Version 1181 1.10, October 1992. 1183 [ND] Narten, T., E. Nordmark, W. Simpson, "Neighbor Discovery 1184 for IP Version 6 (IPv6)", RFC2461, December 1998. 1186 [RFC1469] Pusateri, T., "IP Multicast over Token Ring Local Area 1187 Networks", RFC1469, June 1993. 1189 [RFC2026] Bradner, S., "The Internet Standards Process -- Revision 1190 3", RFC2026, BCP00009, October 1996. 1192 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1193 Requirement Levels", RFC2119, BCP0014, March 1997. 1195 [TKARCH] IBM Token-Ring Network, Architecture Reference, Publication 1196 SC30-3374-02, Third Edition, (September, 1989). 1198 [VRRP-V4] Knight, S., et. al., "Virtual Router Redundancy Protocol", 1199 RFC2338, April 1998. 1201 15. Informative References 1203 [HSRP] Li, T., B. Cole, P. Morton, D. Li, "Cisco Hot Standby 1204 Router Protocol (HSRP)", RFC2281, March 1998. 1206 [IPSTB] Higginson, P., M. Shand, "Development of Router Clusters to 1207 Provide Fast Failover in IP Networks", Digital Technical 1208 Journal, Volume 9 Number 3, Winter 1997. 1210 [OSPF] Moy, J., "OSPF version 2", RFC2328, STD0054, April 1998. 1212 [RIP] Malkin, G., "RIP Version 2", RFC2453, STD0056, November 1213 1998. 1215 16. Author's Address 1217 Robert Hinden 1218 Nokia 1219 313 Fairchild Drive 1220 Mountain View, CA 94043 1221 USA 1223 Phone: +1 650 625-2004 1224 EMail: bob.hinden@nokia.com 1226 17. Changes from RFC2338 1228 - Added new subsection (8.4) with recommendations about setting 1229 priority values and it's relationship to the preempt flag. 1230 - Changed rules for receiving VRRP packets to not drop the packet if 1231 the Adver Interval is not consistent with the local configuration 1232 for the virtual router. Only log and notify network management. 1233 - Reduced granularity of the Advertisement_Interval to centiseconds 1234 (i.e., 1/100 of a second). Changes include: 1235 o Made Adver Int field in the header 12-bits to allow range from 1236 1 to 4096 centiseconds. 1237 o Change Skew_Timer calculation to skew over one 1238 Advertisement_Interval. 1239 - Added switch (Accept_Mode) to control whether a virtual router in 1240 Master state will accept packets addresses to the address owner's 1241 IPv6 address as its own if it is not the IPv6 address owner. 1242 - Changed VMAC assignments to a separate block of IANA Ethernet 1243 addresses and added this to the IANA considerations section. 1244 - Removed different authentication methods, header fields, and 1245 updated the security considerations section to explain the reasons 1246 for doing this. 1247 - General rewrite to change protocol to provide virtual router 1248 functionality from IPv4 to IPv6. Specific changes include: 1249 o Increment VRRP version to 3. 1250 o Change packet format to support an 128-bit IPv6 address. 1251 o Rewrote text to specify IPv6 Neighbor Discovery mechanisms 1252 instead of ARP. 1253 o Changed state machine actions to use Neighbor Discovery 1254 mechanisms. This includes sending unsolicited Neighbor 1255 Advertisements, Receiving Neighbor Solicitations, joining the 1256 appropriate solicited node multicast group, sending Router 1257 Advertisements, and receiving Router Solicitations. 1258 - Revised the section 4 examples text with a clearer description of 1259 mapping of IPv6 address owner, priorities, etc. 1260 - Clarify the section 7.1 text describing address list validation. 1261 - Corrected text in Preempt_Mode definition. 1262 - Changed authentication to be per Virtual Router instead of per 1263 Interface. 1264 - Added new subsection (9.3) stating that VRRP over ATM LANE is 1265 beyond the scope of this document. 1266 - Clarified text describing received packet length check. 1267 - Clarified text describing received authentication check. 1268 - Clarified text describing VRID verification check. 1269 - Added new subsection (8.3) describing need to not forward packets 1270 for adopted IPv6 addresses. 1271 - Added clarification to the security considerations section. 1272 - Added reference for computing the internet checksum. 1273 - Updated references and author information.