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VRF-Aware SNMP on Brocade VDX

SNMP was not designed with VRFs in mind. Querying the routing table via SNMP did not take into account the idea of having multiple routing tables. But clearly it’s something people want to do, so some clever engineers figured out how to shoe-horn VRF contexts in. This week a customer asked me how to query the routing table for the non-default VRF on Brocade VDX switches. Here’s how to do it:

VRF Configuration

I’m using a Brocade 6940 running NOS 7.0.1 here. Note that SNMP configuration changed around NOS 6.x, so if you’re running something older this may work differently.

For this lab I have Loopback 1 in the default VRF, with an IP of 50.50.50.50/32. I’ve created another VRF called “internet”, and put Loopback 2 in that VRF, with IP 60.60.60.60/32. Now I have two different routing tables:

Default SNMP Configuration

Basic SNMP configuration looks like this:

If we poll the inetCidrRouteTable OID (1.3.6.1.2.1.4.24.7), we can see results for the default VRF:

VRF-Aware SNMP

OK, so how do we poll the ‘internet’ VRF routing table?

We need to configure multiple SNMP server context to VRF mapping. Here’s a minimal configuration (added to our earlier config):

Now we can poll our switch using the community string internet, and we’ll get results for that VRF:

Easy as that.

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