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New Member

IP Phones in Different Subnets

I have an interesting problem in that I have to put some IP phones in a different subnet than the CCM is in. My main core switch knows the location of all the subnets but I cannot connect a phone to the call manager if it is in a different subnet. Cisco TAC says it should work but are unable to tell me how.

Any ideas??

I also need to get this resolved to set up a 7960 running through a VPN. How are other people handling IP info for this?


Alan White

Systems Engineer SBC

Cisco Employee

Re: IP Phones in Different Subnets

You say the switch knows the location of all the subnets but how are you routing in between the subnets? Do you have a router connected to the switch providing trunking/encapsultion of vlans?

Any access-lists on the router that could be blocking ports TCP (2000-2002) and UDP (16384-32767) between the subnets?

Can you place a PC on each subnet and ping to each other?

Outside of that, I have 220+ phones on our network that I don't think there are more than 30 on the same subnet and all works great. I'd check your access-lists and make sure you are routing in between subnets correctly.


Re: IP Phones in Different Subnets

If you do have a sounds for me like you didnt set ip helper adress for your dhcp server in the interface of each VLAN.

New Member

Re: IP Phones in Different Subnets

Hello Alan,

This I have exactly that running. Routing is needed between subnets/networks....then setup DHCP with a scope for the new network/subnet....configure it to provide the basics such as ip/mask/gateway...but also setup option 67/150 to provide the IP address/name of the Callmanager server (not 100% sure of the option numbers as I am away from the office and don't have my notes). DNS resolution can also cause problems if there is not an entry for ciscocm1 as this is the default name the IP phones try to resolve to. Once you have those configs....use DHCP to check for the IP address being granted....then check from the phone's status menu to see how far it is can check the network settings on the phone to see if the DHCP settings are taking affect.

Jason Black

Technical Support Advisor

Telus National Systems

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