Unable to Ping private Cable Modem IPs from the CMTS

Unanswered Question
Aug 25th, 2008
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We're having a problem on our cable network.

I'm unable to ping modems directly from the CMTS to the modem private IPs.

As a result we're seeing a number of modems unable to get past init(d) during initialization because the CMTS cant communicate with them.

Double checked DHCP and that does not see the DHCP requests as it normally should.

What makes this issue more complicated is that we're able to ping to these modems private IPs from other locations within the network.

Tracing to the non-routable modem IP shows the CMTS as the hop just before the modem as one would expect.

We see CPE traffic to and from the Internet and I'm able to communicate with the modems at the docsis layer (ping docsis )

After reloading the CMTS, we regain the ability to ping modems and they are able to communicate to DHCP once again at least for a few days.

This has happened on / off for the last few weeks. Things work great for a while then everything goes down hill.

Cisco Internetwork Operating System Software

IOS (tm) 7200 Software (UBR7200-K8PU2-M), Version 12.3(21a)BC1, RELEASE SOFTWARE (fc1

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