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Webcast-Catalyst9k
New Member

uBR arp-cache, setting up CPE static IP

We're implementing static IP's for residential cm customers. Max cpe on docsis file is set to 5. User implements IP on their cpe equip't. and fails to connect.

Pings to the IP hit at 50% success.

Resetting CPE host, and resetting cm on the uBR (7246vxr) change nothing..

However, initiating a ping from the uBR to the cpe IP gives us 100% ping success and connectivity.

Question is, among others - is this ping updating the arp relating to the particular cm in the cpe is connected to? Why is this working once ping'd and nothing else?

I have seen similar effect when issuing the "clear arp-cache" command; but why is the simple 'ping' having such an effect?

Customer is attempting to run a Linksys router attached to the cm, to do some soho-type tasks (vpn, etc.) and am trying to get a handle on the dynamics of what is changing when we set up the statics in relation to the uBR.

Any info/experience in this area is most appreciated.

Thnks

3 REPLIES
New Member

Re: uBR arp-cache, setting up CPE static IP

Check into these commands

Cable Interface config mode:

no cable arp

cable source verify

It sounds like you have no cable arp enabled. I would leave it that way, as it forces your customers to use dhcp - you can give them a static ip at the dhcp server if they want it.

HTH,

Justin

New Member

Re: uBR arp-cache, setting up CPE static IP

don't see either statements in the config; pretty much just no ip mroute-cache is all.

New Member

Re: uBR arp-cache, setting up CPE static IP

further troubleshooting this issue, we have found that running a "ping" doesn't cure it every time.

What we have found is that we can get the linksys to dole dhcp to the cpe, and can ping the uBR 100% from the cpe but cannot get a solid ping to the 7206 connected to the uBR (i7206 is internet gateway). Pinging the interface on the 7206 which is directly connected to the uBR results in 50% loss.

Undoubtedly, this is an issue with arp between the uBR and the 7206.

Any ideas?

Thanks for any assist.

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