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New Member

ISP router issues.


I am good friends with the head engineer of my ISP (Cable modem) provider.

Starting about a month ago, we both noticed an oddity. It happens twice a week usually. What happens is:

1. Anyone can get out to the 'net on the VLANs just fine

2. Any business customer (myself included) running INCOMING services like web/DNS, etc. is not working...looks like there is some odd ARP issue.

Example, I get out to the ne just fine from my LAN, but folks wishing to access my webservers (NAT'd in the LAN) cannot...they ping me and get "TTL expired".

My buddy then clears the ARP cache on the 7206 that serves all of us, and it's fine.

Anyone have any idea what the problem may be? We are stumped.

  • Other Network Infrastructure Subjects
Cisco Employee

Re: ISP router issues.

the TTL expired is an indication that there is a routing loop between 2 devices.

If the routing table is ok, the CEF table (if cef enabled) could be corrupted.

Clearing the arp cache will clear the cef table.

There are a bunch of known CEF bugs like this.

Make sure the 7206 runs one of the latest version.


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