CISCO 2811 Router and MPLS

rahe010797 · ‎02-06-2015

I have a 2811 router connected to a MPLS (MetroNet) fibre switch via a CISCO 2950 switch. The local and remote routers have tunnel interfaces to connect over the link. The circuit works most of the time but occasionally drops instantaneously and comes right back up. Is this normal for MPLS ? The only log indication are a few outgoing dropped packets on the tunnels at either end. There is no indication of a physical interface problem.

I have changed cables, ports, forced all ports to 100MB/FDX and even taken out the 2950 temporarily but the problem gets worse, without the 2950 i.e. the link stays down until the MPLS switch or physical interface is reset. We have changed the MPLS switch but the same thing happens. There does not appear to be a capacity problem on the 2811 or 2950 although I have only checked CPU and memory.

Has anyone seen this problem, particularly in a real time processing environment ? I have run out of things to try and the provider just says the circuit is fine.

Ronald

Leo Laohoo · ‎02-06-2015

The circuit works most of the time but occasionally drops instantaneously and comes right back up. Is this normal for MPLS ? The only log indication are a few outgoing dropped packets on the tunnels at either end. There is no indication of a physical interface problem.

Can you draw your network diagram here? In your diagram, can you also point out which are is managed by your ISP?

Peter Paluch · ‎02-07-2015

Hi Ronald and Leo,

Please allow me to join.

Ronald, in addition to the diagram Leo requested and which will help us understand your network setup, is it actually possible for you to attach the running-config of your router (sensitive info removed of course)?

Also, you say that the only indication of the circuit going down and coming back up is a few dropped packets on a tunnel endpoint. Can you post the output of the command by which you have determined that packet losses are occurring? By the way, what tunnels are you using - GRE? There are no tunnel interfaces with respect to MPLS (save for Traffic Engineering).

You also say that the "link stays down" - how do you determine that?

Best regards,
Peter

rahe010797 · ‎02-09-2015

I have attached a text file with the relevant sections of the 2811 and 2950 configs. I have snmp 3 active on the link and can see when the traffic goes to zero and an alarm raised when ip sla (icmp echo) does not get a response from the remote end.

The tunnel interfaces are GRE. The drops are shown in the show interface output as shown on the attached text file. The 2811 and 2950 are ours the ISP Fibre switch is not.

Again theer is no indication of a physical fault on the local or remote end. The config on the remote end mirrors the local end except the remote router is a 1941 and there is no remote 2950 switch.