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Re: [OSPF] SR 612546021 - SNMP responses for the "ospfNbrTable" mib variable

[followups to cs-ospf]

Hi Joe,

Responses inline:

Anirban Karmakar (akarmaka) wrote:

Adding ospf mailer list


*From:* Joe Reekers (jreekers)
*Sent:* Friday, October 02, 2009 9:01 PM
*To:* cs-snmp (mailer list); cse-tac-snmp(mailer list)
*Subject:* SR 612546021 - SNMP responses for the "ospfNbrTable" mib variable


*2nd try - expanding audience*


7206VXR IOS 12.3(22)


Hi Team.
I need some assistance with this case. Polling of the "ospfNbrTable" mib variable is yeilding an improper response. I believe that the SNMP response should match with the router show command as seen by dumping OSPF neighbours. 

For example,
On a router (Bucaramanga), they have the following OSPF neighbours as seen from the router CLI: 

cobuar1#sh ip ospf neigh
Neighbor ID Pri State Dead Time Address Interface
172.28.4.40 1 FULL/DR 00:00:30 10.166.28.6 ATM3/0.19046 10.10.66.32 0 FULL/ - 00:00:37 10.10.66.32 Serial2/0:0 10.10.66.32 0 FULL/ - 00:00:39 10.10.66.32 Serial2/4:0 


However the IP addresses show up as 0.0.0.0 in SNMP queries on ospfNbrTable

These results should match with entries under "Address" column above:
ospf.ospfNbrTable.ospfNbrEntry.ospfNbrIpAddr.10.166.28.6.0 : IpAddress: 10.166.28.6 

ospf.ospfNbrTable.ospfNbrEntry.ospfNbrIpAddr.0.0.0.0.21 : IpAddress: 0.0.0.0
ospf.ospfNbrTable.ospfNbrEntry.ospfNbrIpAddr.0.0.0.0.23 : IpAddress: 0.0.0.0

These results should match with entries under "Neighbor ID" column above.
ospf.ospfNbrTable.ospfNbrEntry.ospfNbrRtrId.10.166.28.6.0 : IpAddress: 172.28.4.40
ospf.ospfNbrTable.ospfNbrEntry.ospfNbrRtrId.0.0.0.0.21 : IpAddress: 10.10.66.32 ospf.ospfNbrTable.ospfNbrEntry.ospfNbrRtrId.0.0.0.0.23 : IpAddress: 10.10.66.32 

This MIB object states the following:

ospfNbrIpAddr OBJECT-TYPE
       SYNTAX       IpAddress
       MAX-ACCESS   read-only -- read-only since originally an
                              -- SMIv1 index
       STATUS       current
       DESCRIPTION
          "The IP address this neighbor is using in its
          IP source address.  Note that, on addressless
          links, this will not be 0.0.0.0 but the
          address of another of the neighbor's interfaces."

       ::= { ospfNbrEntry 1 }
At first, I thought this may be CSCdz53031, but that's been ruled-out based on the show tech received that doesn't show unused ospf process definitions. 


So, my questions are:
1. In the first poll, you see that the IP is included in the poll, but the instance is "0", but it returns a value...is that the correct way to poll this object?
(ex. ospf.ospfNbrTable.ospfNbrEntry.ospfNbrIpAddr.10.166.28.6.0 : IpAddress: 10.166.28.6) 

What I think is being displayed here is the table index, defined as:

INDEX { ospfNbrIpAddr, ospfNbrAddressLessIndex }
It so happens that the first interface is numbered, so ospfNbrAddressLessIndex will be 0 as specified in the MIB: 

    ospfNbrAddressLessIndex OBJECT-TYPE
        SYNTAX   InterfaceIndex
        MAX-ACCESS   read-only
        STATUS   current
        DESCRIPTION
           "On an interface having an  IP  Address,  zero.
           On  addressless  interfaces,  the corresponding
           value of ifIndex in the Internet Standard  MIB.
           On  row  creation, this can be derived from the
           instance."
2. In the other two polls, the IP in the poll is 0.0.0.0, but the instances match the ifTable, yet the information returned is also 0.0.0.0...would that be expected??
(ex. ospf.ospfNbrTable.ospfNbrEntry.ospfNbrIpAddr.0.0.0.0.21 : IpAddress: 0.0.0.0 ospf.ospfNbrTable.ospfNbrEntry.ospfNbrIpAddr.0.0.0.0.23 : IpAddress: 0.0.0.0)
I agree this looks fishy. If I had to guess, I'd say the code in this area was never updated when we moved from rfc 1253 to rfc 1850. In the older version of the MIB the definition was: 

     ospfNbrIpAddr OBJECT-TYPE
         SYNTAX   IpAddress
         ACCESS   read-write
         STATUS   mandatory
         DESCRIPTION
            "The IP address of this neighbor."
         ::= { ospfNbrEntry 1 }

So, for unnumbered interfaces this is returned as 0.0.0.0.

Feel free to file a bug against ospf for this.

Regards,
Paul
I guess I'm not understanding what should be polled and returned as compared to what they are actually seeing here. 


Files:
Show Tech: http://wwwin-tools.cisco.com/casekwery/getAttachment?id=30975569&download=Y <http://wwwin-tools.cisco.com/casekwery/getAttachment?id=30975569&download=Y>
IfTable walk: http://wwwin-tools.cisco.com/casekwery/getAttachment?id=30975562&download=Y <http://wwwin-tools.cisco.com/casekwery/getAttachment?id=30975562&download=Y>
Word Doc with some additional data: http://wwwin-tools.cisco.com/casekwery/getAttachment?id=30942401&download=Y <http://wwwin-tools.cisco.com/casekwery/getAttachment?id=30942401&download=Y> 


Thanks in advance for your help.


-Joe