irb and dhcp problems

Unanswered Question
Dec 22nd, 2007

HI all

I have 2x cisco routers connected back to back with an ethernet connection to my cable modem. The router connected to my cable modem is configured with irb and setup as a transparent IPS. The second router is configured with the new cbac zone based firewall which then connects to my Private network.

The setup works fine for a number of days then I find I cannot connect to the internet. When I look at the router connected to my LAN it has no ip address. With debugging I can see the DHCP requests but I am getting no replies. If I plug my cable modem directly into my first router (bypassing the irb router) it gets an address no problem. I can then reconnect the irb router and it works fine again for a period of time.

When its in the failed state I see the arp table on the irb router shows my public IP address as incomplete and debugging on my first router shows no UDP packets recieved yet I see plenty on the IRB router.

Does anyone know what the problem is or how I can look at the mac addresses in the UDP packets? Is there any other tables I should be looking at?

Thanks

I have this problem too.
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htarra Fri, 12/28/2007 - 12:42

i think you cannot seeing udp, but you can see a lot of tcp. Not to say that this is unusual. This tcp traffic seems to be occurring on network .Looks like a UDP packet get sent to the Ciscoworks server on port 16236. But what should it contain? After re-initializing UT table yesterday, only 1 username populates out of thousands of entries (MAC addresses).

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