Cisco ip 7920 & networking

Unanswered Question
Aug 19th, 2009

Hi I have a simple question.

Does a cisco 7920 ip phone work if he is not in the network the call manager is?

I mean the 7920 has a gateway that allows him to comunicate. But he cannot download the config file and he can not connect to callmanager.

Or the 7920 to work must be in the same vlan?


I have this problem too.
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Manuel Azevedo Wed, 08/19/2009 - 03:39


Assuming you have routing working ok:

* If you use DHCP you need to set option 150 with the IP address of Callmanager that has the TFTP server running;

* If you don't use DHCP (manual IP address) or use a DHCP that does not permit you add or change option 150, you just need to set "Use alternate TFTP" and set the IP address of the TFTP server.



Manuel Azevedo Wed, 08/19/2009 - 04:18

Assuming you use a Cisco IOS as a DHCP server:

ip dhcp pool IPTEL


option 150 ip




Assume we have two Callmanager servers with TFTP servers activated ( and In this you see option 150 has both CCMs (first and

If you use a Windows (or Callmanager 3.x and 4.x) machine that creates DHCP, you need to set the options in the DHCP configuration - either globably (for all scopes) or just on the scope you want.

If you use Callmanager (5.x, 6.x and 7.x) you can set up DHCP pools directly in the CCM and setup option 150 there as well.



languedoc Wed, 08/19/2009 - 04:20


I use dhcp, but in the phone I set up TFTP Option as static and I entered the ip addres of the call manager express.


languedoc Wed, 08/19/2009 - 04:30


In one vlan there is the call manager with cisco ip phones 7905 working properly , this call manager has a dhcp server wich gives ip address for this vlan lets say

In the other vlan we have the cisco ip phone 7920, a dhcp server wich give ip address for this vlan lets say

the communication bettwen is ensured via the gateways.

In the cisco ip phone 7920 I use dhcp, but I set up "TFTP Option" as static and I entered the ip addres of the call manager express


Manuel Azevedo Wed, 08/19/2009 - 05:05

If you have a PC on the same vlan of the phone, try this:

- Supose the IP of the CCM is and the MAC of the phone is: 123456789012

tftp get SEP12345679012.cnf.xml

Do you get the file?

Manuel Azevedo Wed, 08/19/2009 - 05:20

And if you do this on the same vlan as Callmanager you can?

If this is so, do you have any access list that limits communications between the two vlans?

Do you have the default router/gateway configured correctly for both vlans?

Can you ping from the PC to Callmanager?

languedoc Wed, 08/19/2009 - 07:52

in the same vlan as the call manager i get a file .raw but the cnf.xml does not exits. So I added a tftp in the 7920 vlan and I added the .cnf.xml. Now the telephone get the file and it is connected. The only problem is that I can talk but I can not hear.

I wonder if it is my pix who is causing me problems.



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