ASK THE EXPERT- SNMP- clagAggPortListPorts Nexus7K

[ww9rivers]

Problem: To find members of a port-channel on a Nexus 7K running NX-OS 4.2(3)

Background notes: http://bit.ly/a9VHHE

From my reading of the CISCO-LAG-MIB, the clagAggPortListPorts on a port-channel provides a list of interfaces in that port channel:

This  object contains a list of ports currently associated with this  Aggregator in the format of  '[number_of_ports][cieIfDot1dBaseMappingPort1][...]  [cieIfDot1dBaseMappingPortn]'

However, although the Nexus 7K claims to support the CISCO-IF-EXTENSION-MIB in 4.2(3), but it does not seem to provide the cieIfDot1dBaseMappingPort object.

So, now from this:

CISCO-LAG-MIB::clagAggPortListPorts.369098873 = Hex-STRING: 00 01 03 89

I can see that the port channel has one interface in it which is cieIfDot1dBaseMappingPort 0x389 (905). How do I map that to an interface on the switch?

[Joe Clarke]

There is a bug open requesting feature parity between the Cat6K and the Nexus when it comes to the CISCO-IF-EXTENSION-MIB (CSCsr21316).  The bug is currently being worked on, but there is no ETA on when support will be added.  One other customer reported this same problem, but no good resolution was found.  I wonder if you might be able to get this data using the dot1dBasePortIfIndex from the BRIDGE-MIB.  I do not have a Nexus on which to test, but it's worth a shot.

[ww9rivers]

Joe,

Thanks for the information. That is helpful.

But unfortunately, according to the page on Nexus7K MIBs, the BRIDGE-MIB::dot1dBasePortTable is supported in 5.0(2), not in 4.x -- which does match my test. I guess I'll have to wait for a change to upgrade the code.

Regards,

--

Wei

[Scott Aitken]

Hi Rivers,

I've been searching for the same OID myself.

cieIfDot1dBaseMappingPort is at 1.3.6.1.4.1.9.9.276.1.5.1.1.1 which doesn't seem to exist on NX-OS (4.2(1)N2(1)).

One of my port channel entries in the CISCO-LAG-MIB::clagAggPortListPorts OID has the value:

0x000200930094

I worked out that there are two interfaces (0x0002), which are interface (0x0093) and interface (0x0094).

Converting these to decimal I get (147) and (148).  If I subtract 128 (not sure why), I get 19 and 20.

These correspond to Et1/19 and Et1/20.

I'm trying to work out your port number from 0x389.

It could be:

3/1/9 (probably not)

or:

4/9 (which is (0x3 + (0x89 / 0x80) = 4) / (0x89 % 0x80 = 9))

or:

7/9 (which is (0x389 / 0x80 = 7) / (0x389 % 0x80 = 9))

Are any of these correct?

Regards

Scott

[ww9rivers]

Hi, Scott,

Your finding does compute with my NX7K configuration. The port 0x389 maps to port 7/9 with your formula.

So I guess, the formula is:

     slot = floor(cieIfDot1dBaseMappingPort / 128);

     port = cieIfDot1dBaseMappingPort % 128;

128 is likely the maximum number of ports per line card at Cisco.

The thing is, without Cisco documenting 0x0093 means port 1/19, we can only call that a guess. If the BRIDGE-MIB is availabile, then the dot1dBasePort number is mapped over to ifIndex, guessing would not be needed anymore.

Thanks for the information.

--

Wei