Cisco IP Phones and odd IP addresses

Unanswered Question
Jun 29th, 2009

OK, I thought we had this solved, but apperently we only mitigated it. For whatever reason, our Cisco IP phones are gravitating to even DHCP IP addresses.

I think it works something like this: When a phone first comes up, it grabs the first available IP address (from the DCHP server, which in our case is running on the Cisco gateway). However, when it comes time to renew, if the phone is using an odd IP address, the renewal doesn't happen and the phone is assigned the next available IP address. This process continues until all phones have even IP address. The problem is that this means the phones are forced to reset whenever their DHCP lease expires until they find their even address. And I have no idea what is wrong with the odd IP addresses.

Has anyone seen this? Is anyone using DHCP running on the Cisco IOS able to use odd IP addresses? Even if you have no clue why it's happening, either, please let me know if this is just me (because I'm seeing it at multiple sites) or if this is common with Cisco IOS DHCP servers.

I have this problem too.
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davidme Wed, 07/01/2009 - 11:18


I regularly configure DHCP on Cisco voice gateways and have never come across this problem.

As a test - what happens if you create a scope somewhere else (like on a switch) - do the phones still have this odd IP address problem?

I'm intrigued as to what is causing this...



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