No router addresses collected on a Cisco Nexus 7000

[Morten Brekkevold]

After applying the fix for bug 777821, which was reported for a Cisco Nexus 7000 routing switch, the ipdevpoll polling job finishes, but no router addresses are found - therefore none of the router ports will show up.

The Nexus appears to support both the deprecated IP-MIB::ipAddrTable and the preferred IP-MIB::ipAddressTable (which is address-type/version agnostic). ipdevpoll appears to use only the ipAddressTable when available, but the Nexus appears to have a bug in its support for this table.

The ipAddressPrefix column in this table uses RowPointer syntax to point to a conceptual row of the IP-MIB::ipAddressPrefixTable, indicating which prefix the IP address belongs to. The Nexus switch appears to produce invalid RowPointers in the table - the OID pointers do not include a column sub-index, which causes ipdevpoll to ignore the IP/prefix entry.

The RowPointer, as defined by the SNMPv2-TC module, is described thus:

            "Represents a pointer to a conceptual row. The value is the
            name of the instance of the first accessible columnar object
            in the conceptual row.

            For example, ifIndex.3 would point to the 3rd row in the
            ifTable (note that if ifIndex were not-accessible, then
            ifDescr.3 would be used instead)."

[Morten Brekkevold (mbrekkevold)]

So, the problem here seems to be that ipdevpoll gets some results from the ipAddressTable, and therefore doesn't proceed to the ipAddrTable.

The simplest solution would be to query both, always, and merge the results.

[Morten Brekkevold (mbrekkevold)]

fix here: http://metanav.uninett.no/hg/series/3.8.x/rev/1f2881787848

[Morten Brekkevold (mbrekkevold)]

A similar issue for machine tracking data (IP/MAC mappings from IP-MIB) is described in bug 782161