Interface ID in Cisco switches and sflow

[Manuel Perdomo]

Hello,

I've configured some Cisco switches with sflow but I get some strange interface identifiers, something like this:

...
in_if : 369,098,810
out_if: 369,098,809
...
in_if : 369,098,754
out_if: 369,098,809
...

Can a mapping be performed with interface names?

Thanks,
Regards

[Neil McKee]

In the sFlow spec these are defined to be SNMP ifIndex numbers.  That means you should be able to retrieve the ifName with a query like this:

snmpget -v 2c -c <community> <agentIP> .1.3.6.1.2.1.31.1.1.1.1.<ifIndex>

Or are you saying that those numbers do not appear in the ifTable?

(Note: these are supposed to be the ifIndex numbers of the port, not a virtual sub-interface that represents, e.g. a VLAN on that port.)

The sFlow spec allows for the ifName to be shared as an optional extension to the interface-counters message, which can be helpful when SNMP is not available.  However not all vendors have added this extension:

https://sflow.org/sflow_openflow.txt

Example here:

https://github.com/sflow/host-sflow/blob/890c3e7ec116f344a4101b77d62dad6c74c6cb41/src/Linux/hsflowd.c#L566-L581

If Cisco added the extension to this agent then you should see the port names in, e.g. the sflowtool output:

https://github.com/sflow/sflowtool

------
Neil McKee
InMon Corp.

--
You received this message because you are subscribed to the Google Groups "sFlow" group.
To unsubscribe from this group and stop receiving emails from it, send an email to sflow+un...@googlegroups.com.
To view this discussion visit https://groups.google.com/d/msgid/sflow/96fb1b58-4cf0-4ec2-aa78-a5da56b38573n%40googlegroups.com.

[Manuel Perdomo]

Yes, that was what I was looking for, knowing that it is the ifindex I was able to get the name of the interfaces with "show interface snmp-ifindex"

Many thanks,

Regards