Understanding vlan interface counters

[m-menozzi]

One customer is blaming that on a MSFC card the statistics shown on the show interface vlan output (in terms of received and transmitted packet) are not real.

He doubts that what is shown there are really all frames received by this VLAN.

For what I see on docs the statistic on the MSFC VLAN interfaces should show every packet received even if is hardware switched by the PFC.

Is it true or is the customer right, this time ?

Thanks

Marco

[wkumari]

I think your customer is smoking something (but who knows, mebe he is right and we are smoking something!), I have never heard this...

You could look at the interface counters in the VLAN and add up the numbers and compare them to the MSFC...

[m-menozzi]

Well probably you are right. Infact I have just been told from him that he's not afraid about tx/rx packets but he doesn't understand the input/output rate counters that in his opinion should be higher.

Marco

[tracey.marshall]

My customer has a similar problem. It occurred when the Catalyst 6509 SE was upgraded from 12.1(11b)E4 to 12.1(13)E. They used to use "show interface vlan" but are finding that the packet/byte counts are too low. The "show vlan counters" command was introduced in 12.1(13)E and it seems to give better results. I am now trying to find out if there is an oid for this command so that my customer can use this with their snmp manager. Anyone have any info on this?

[t.baranski]

Marco, can you show me where in the docs it says that the VLAN counters should reflect all packets even if the packets never make it to the MSFC (i.e., if MLS is being used)? I ask because I've ran into counter issues as well, and just assumed that VLAN counters aren't reliable because of things like MLS.

[m-menozzi]

I don't find this page anymore, I'm sorry for that.

At the beginning I thought the same as you: I supposed that only candidate packets should be present on the VLAN interface counters especially on 6x00 where MLS is enabled by default with CEF.

Instead I found that page that right now I'm not able to find anymore (I spent one hour to search it and I'm afraid that I didn't save the URL before), where it was sentenced that the show interface should include all traffic also the one mls switched.

Marco

[bsaul]

I have come across this issue on the 65xx w/MSFC. What I found to be the best is to look at the physical ports (ie. on the "switch" side). I have found hat these counters are correct.

As for the Vlan counters: MLS is enabled by default on the 65xxx w/MSFC and therefore only the first packet it forwarded to the MSFC and then an entry is created in the MLS cache and L2 switched from that point on. You can change/adjust all the MLS settings to tweak your performance. If you have a large network you will want to take a good hard look at the aging time. We got almost 25% CPU time back from an adjustment to our aging policy.