Problem on Cisco 871

Unanswered Question
Nov 20th, 2008
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Hi, all, I've a little problem.

I configured my 871 to take IP address from the WAN interface, a D-link modem.

The modem send via DHCP the information that the router needs to operate.

...all still works, but, I've this error in the log:

Looping packet detected and dropped -src=my public IP dst= d-link modem) hl=20 tl=604 prot=17 sport=68 dport=67inFastEthernet4, nexthop=mypublicIP

This error every 2 minuts! After a day the router needs to reset because I can't surfing the web and I can't reach him via telnet or web browser.

The problem can be the DHCP? (port 67 and 68 mumble)....


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mihanlin Sun, 11/23/2008 - 01:58
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This is typically a problem with the configuration on your router.

A very common cause is a misconfiguration of an IP helper address for DHCP. The helper address should be the same address as that of the server of the intended service. Putting the address of the router in the helper address causes a routing loop to be created.

I've also seen this with static routes pointing to itself. So, I recommend you check that aswell.




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