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Ubr10K Arp issue

  When upgrading to 12.2(33)SCC3 code we started seeing customers who have ASA and sonicwall firewalls having arp issues with static IP's sitting behind the firewall on there DMZ's  When looking into this we noticed it is only on our MC20x20 card that it appears to be happening on.  Is this an issue with these firealls and proxy arp or could it be the arp filtering that is automatically configured when migrating ot the SCC3 code.


Cisco Employee

Re: Ubr10K Arp issue

Hi Jeremy,

The MC2020 and the MC520 cards should not play a role in the way the ARP requests and replied are handled, that process is left to the CMTS route processor. It is possible there are some configuration settings which may be causing issues with the ARP behavior.

Can you tell me more about the issue? Is it happening consistently with those static CPE IPs? Does it work for 60 minutes then stop working? Is it always the same issue?

If you can post the interface bundle configuration I can take a look.

Couple possible points to look into:

1. Cable arp filters (defaults to 3 every 2 seconds for request and replies)

2. "Cable source-verify [dhcp]" and "no cable arp" - changes the behavior of how CPE ip addresses make it into the CMTS ARP table

3. "Cable trust"  - Affects the way the CPE IP makes it into the ARP table.

Lastly, if you have a valid service contract I strongly suggest you open a TAC Service Request as they can commit a Cisco engineer to working with you.



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