Hi,

We're currently in the process of mapping our networks out. We're using a combination of SNMP to collect various bits of data, then throwing it all at graphviz to produce a webpage we can show people to prove its not the network when a server stops responding due to some idiot turning it off (again).

This is all fine, but we've now been asked to highlight which are the root ports on the various switches. I have no idea why, I've just been told to sort it out.

I've trawled through the Cisco MIB page and found a couple of things that looked promising, but always got an empty return when queried, so does anyone know what I need to query to get the root port of a specific instance.

Thanks in advance

J

you could have different root ports for different vlans on the same switch in the specific instance.

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1.3.6.1.2.1.17.2.7 dot1dStpRootPort looks promising.

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What Infinite said. For other instances, you'll need to specify the context in the community string.

E.g. If your community string is 'private' and you want to find the root port in vlan 100, then poll with the community 'private@100'.

Also, you should look into the Cisco STP extensions MIB, which gives you a lot more information than bridge MIB.

That's one of the ones I tried and got no response, however...


Doing the above gets it to respond with a port identifier

Thanks gents, now got to work out how to make the diagram look like it came out of visio...

Cheers

J

Edit: First I've got to work out how the result from the above (26) is indexed to anything that resembles an ifIndex or ifDesc.

I thought it returned an ifIndex from IF-MIB. Isn't that what you're looking for?

If I query the dot1dStpRootPort I get this:

The root port on vlan 10 is g0/2, which I can believe is the 26th port, if I query the IF-MOB stuff, I get
What I'm looking for now is a link between the two.

Sorry if this is obvious & I'm being stupid, SNMP is kind of new to me.

Cheers

J

I believe 26 refers to the STP interface index, which is mapped to the ifTable.ifIndex in another table in one of the STP mibs. Not sure which but can look it up after my commute.

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Ahh, interesting. It happened to be the same on old IOS, but is now different on newer IOS where ifIndex == entityMIB index.

Ok, better add in checking the IOS to decide what to query as well then, this looked so easy on paper...

Cheers

J

Well I'm sure there is a table somewhere that correlates the index in bridge MIB with the ifindex in ifmib. You just have to find it. . Start digging through the MIB. Cisco has a nice MIB browser tool. Just google for Cisco MIB browser and then search for BRIDGE-MIB, or your specific OID. The MIB should specify what will be returned as a result.