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Cisco 871 stops forwarding traffic

I'm running a Cisco 871 router in a LAN WAN setup. Nat, site-to-site VPN, Firewalling, etc. The problem is that the router stops forwarding traffic at random. The only way to fix this issue is to reboot the router using the console / powerswitch. Symptoms are as following:

  • Router response times suddenly go through the roof (up to 1000 msec) until, after a few minutes, the router becomes totally unresponsive.
  • After the router crashes, it cannot be pinged at all.
  • When I connect a console cable to the router, I can use it like normal.
    • show proc cpu hist -> normal cpu load.
    • counters on interfaces do not increment.
    • logging does not show any strange output.
    • shut/no shut on an interface has no success
    • ping from the router to another device does not work.

I've tried several advsecurity IOS versions, 124-15T 124-24T. All the versions have the same symptoms.

Anyone any idea?

Everyone's tags (3)
Cisco Employee

Re: Cisco 871 stops forwarding traffic

I suggest you open a TAC SR to troubleshoot this.

Some other troubleshooting options:

- disable cef and ping.

- check input queues in show int. maybe it's wedged, you would see something like Input queue:76/75

- check buffers in show buffers : are there failures ?, is the total counter unusually high?

- is IOS 15.0 also failing?