Detecting LDP Session status via SNMP

[colin.murray]

Hi, I want to monitor LDP Sessions in MPLS VPN - specifically alarm if a session goes down.

It is possible to configure SNMP traps for mpls ldp session down, but the problem is: the router tries to send the Trap label-switched!! I have seen this in the lab with Syslog - the syslog message about the ldp session going down is seen on the CLI, but it never reaches the Syslog server. When the ldp session comes back up, I get the notification on both the CLI and the syslog server.

Is there an SNMP OID I can check to see number of ldp sessions active? I think it should be mplsLdpSessionState, but it shows up as "inactive" on the Cisco SNMP Object Navigator, and I can't read it off the router (7200 ios 12.3.9b)

Is there any way I can detect if a session is down???????

Thanks.

Col.

[mmolina2]

I'm not a big SNMP guy so I honestly don't know if this is possible. Perhaps you can configure the SNMP trap source to be an interface that the syslog server doesn't reach by label switching.

[colin.murray]

Thanks for the feedback. We currently use the loopback as the trap source, but the trap is still label switched the instant it is generated. One option would be if it could repeatedly send a trap (say every 30 seconds). I don't think this is possible though, so I may have to use a script to telnet to each router and read the tdp neighbourship, but that's pretty clumsy...

[oettls]

you could use LDP advertise lists to only distribute labels for prefixes you really need to be label switched. Common would be to only advertise labels for BGP next-hops (normally PE loopback addresses).

In your case prefixes where your mgmt systems sit (trap destination) seem to be label switched.

cheers,

Stefan