[cisco-voip] UCM7 won't ACK DHCP Request for remote site phones

[Mark Holloway]

The router at the remote site is using an ip helper-address. The help address is the IP of the DHCP Server (UCM7 PUB) at the main location.  tshark/wireshark at the main location confirms the DHCP packets are in fact arriving at the main location as the phone boots.  Looking at wireshark for a phone that boots at the main location, the DHCP Discover and Request looks the same only UCM ACK's the DHCP requests and provides an all the appropriate IP information.  Considering I can take phones from the remote site and power them up at the main site with no problems but then they fail again at the remote site is very strange. Erasing the phone config on the phone or doing a factory reset doesn't help.   I'm lost.


On Dec 2, 2009, at 4:40 PM, Wes Sisk wrote:

> The remote phones would likely have a 'relay agent' set that helps to identify what IP range should be used to issue the address.  Is the relay-agent field coming through?  Is there an appropriate DHCP scope defined that covers the IP of the relay agent?
> 
> /wes
> 
> On Wednesday, December 02, 2009 6:29:55 PM, Mark Holloway <mh at markholloway.com> wrote:
>> UCM 7.1.3 is configured as DHCP server providing addresses for multiple subnets both locally and at remote branch offices.  7965 phones on same site as UCM acquire DHCP on the voice vlan just fine and register with UCM.  Phones at remote sites are not acquiring DHCP.  I ran a tshark packet capture on UCM VLAN and I see the DHCP requests from the phones at the branch sites arriving at the UCM site as expected.  Remote phones are sending DHCP Discover and DHCP Request but its as if UCM ignores the DHCP Request.  I can take the phone from one of the remote sites and physically plug into the voice vlan at the same site as UCM and it works fine. 
>> Has anyone seen this behavior? 
>> Regards,
>> Mark
>> 
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