Pings to LAN interface of router much higher than WAN interface.

[willb1]

Running into a strange issue that started a few days ago. Noticed higher than usual latency between our branch offices. Running various ping tests I noticed that pings to the WAN (GE0/0) interface are much lower than the LAN (GE0/1) interface on our external 2901 router; a 35+ms difference. This router has a basic config & has been in place for several years. It's well past its hardware refresh date, so replacing it certainly is an option. 

Checking the CPU & memory usage reveals nothing out of the ordinary. Attached is a sanitized config & sh int txt file.

[Philip D'Ath]

Nothing stands out as wrong to me. Perhaps try giving it a reboot.

[willb1]

I should have noted that I did reboot the router. I did not, however, completely disconnect the power then power it back on.

[Joseph W. Doherty]

This is ping from the "outside"? It appears transiting the 2901, from the outside, takes an additional 35ms?

Why the inside interface egress policy with a shaper? (Actually your posted conf and interface stats don't appear to agree on what interface is being shaped.)

If you shaper is on the outside interface (which you interface stats seem to shoe), it might be pinging the outside interface, from the outside, doesn't hit the shaper, but pinging anything beyond that shapes the ping's reply. Possibly that accounts for the additional delay.

[willb1]

Yes, the pings are from the outside. I'll double check the shaper policy but that was put in place after the issue began occurring.

[Joseph W. Doherty]

Intesting.

Well, remember with Cisco devices, they give low priority to dealing with ping replies. I.e. this might be perfectly "normal". However, your diagram shows the same results when pinging through the firewall. If that's correct, it seems strange indeed the router would add so much latency.

[willb1]

We haven't had this issue in the past. We have a basic connectivity monitor setup which graphs the latency between our sites. Several days ago the latency for all locations jumped. Initially I thought it was an issue with my provider, but after discovering the increased latency described above, it looks like that router is having issues.

[Joseph W. Doherty]

If you can work it into a maintenance window, you might try reloading the router.

I've only encountered it very rarely, but I have seen Cisco device become "sick", in that they continue to work mostly, by not doing everything correctly. For such, a reload often restored correct operation.

[willb1 · Accepted solution]

I cycled the power on the router but am still seeing the high latency. I've ordered a replacement. Thank you everyone for your suggestions!