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7960's not accepting DHCP

We have CCM running 3.3(4) and new 7960 phones right out of the box will not accept the DHCP address and register witht hte CCM from across the campus. If I take the phone to the building with the CCM, it registers with DHCP and the CCM and then can be taken to any other building and register just fine. We have Option 150 applied for the buildings we are trying to register from, but teh sniffer trace show a NAC of the dhcp offering. Any ideas???

Community Member

Re: 7960's not accepting DHCP

Are other phones in this building working ok?

Is there a DHCP server on this building's voice vlan, or are you using IP HELPER-ADDRESS?

Have you tried putting a PC on an access port for that vlan to see if it can get an address?

Also (depending on which switches you're using), I once had a problem where i had been using 802.1q trunking and native vlan for most ports with phones attached to them, and accidentally set the same for my DHCP server. even though the IP HELPER-ADDRESS was set correctly it still caused DHCP leases not to get through. Make sure your DHCP server is on an access port.


Community Member

Re: 7960's not accepting DHCP

This bit me also... We moved our DHCP server from Win2k to Win2003, and once I unpluged a phone and reconnected it, it would not obtain an address any more. Existing phones were renewing fine... I checked my DHCP logs and it was issuing NACKS for the data vlan. I check my server's port and I had the Voice vlan also assigned. I removed it and boom the phone pulled an ip and registered...

Best I can think is the Win2003 NIC drivers started trying to talk on both vlans...

What fun...

Community Member

Re: 7960's not accepting DHCP

Hi Don,

It isnt clear when you say that the phones are not registering with DHCP - is it that they are not getting IP address from the DHCP server, or is it that they are not getting the TFTP server address and not registering with the Callmanager?

If the issue is that, when you plug in the phone to the switchport in this building (where u dont have the CM), it doesnt get an address from the DHCP and register with the CM, then please check the switchport configuration.

Why don't you paste the switch configuration?

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