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IP phones across vpn tunnel

lcaruso
Level 6
Level 6

Hi,

I just brought up a new ASA connected site which has a vpn tunnel back to a central hub site which has an AllWorx PBX. I'm told the IP phones at the new site have to be configured with the IP address of the PBX back at the central site and that this can be done with DHCP option 66.

I'm not familiar with how an IP phone gets the address of a PBX at a remote site with DHCP. Can some please shed some light on this for me?

How do I configure this? How does it work? Thanks.

1 Accepted Solution

Accepted Solutions

Hello,

The IP phone need to regester to the callserver/PBX and it all depend on Vendor how the phone gets it. We use Avaya in my environment and on the FW, we have dhcpd option 176 configured for remote office ip phones. My case , does not work with 'auto config'.

dhcpd option 176 ascii MCIPADD=10.1.20.30,10.1.20.31,MCPORT=1719,TFTPSRVR=192.168.70.100,L2QVLAN=0,VLANTEST=60

10.1.20.30/31 --> 2 Call servers.

I read somewhere that option 66 with advanced phones. It replaces option 176.

hth

MS

View solution in original post

5 Replies 5

Shrikant Sundaresh
Cisco Employee
Cisco Employee

Hi Icuraso,

As I understand, the topology is like this:

PBX ------------ (in)ASA-central(out) ============VPN============(out)ASA-remote(in)----------------- Phone

So now, on the DHCP server for IP Phone VLANs on the remote site, you would set that option 66 should be the PBX ip address.


On the Crypto maps for the L2L tunnel on remote asa, we have to make sure, that traffic is allowed from ip phones to PBX server, and vice versa at the other end. (Tunnel may need to be brought up again. Not sure.)

-Shrikant

PS: Please mark the question resolved, if it has been answered, and please rate helpful posts as well. Thanks.

Hi,

Sorry for the delay in responding.

I have all a spoke site that is working that I did not configure, but it is not using DHCP option 66. All it has is DHCP auto config outside.

Both the hub site and all spoke sites allow all address within their subnets in the nat exemption and interesting traffic crypto maps.

Does DHCP auto config outside have a similiar effect as option 66 for these ip phones?

Hello,

The IP phone need to regester to the callserver/PBX and it all depend on Vendor how the phone gets it. We use Avaya in my environment and on the FW, we have dhcpd option 176 configured for remote office ip phones. My case , does not work with 'auto config'.

dhcpd option 176 ascii MCIPADD=10.1.20.30,10.1.20.31,MCPORT=1719,TFTPSRVR=192.168.70.100,L2QVLAN=0,VLANTEST=60

10.1.20.30/31 --> 2 Call servers.

I read somewhere that option 66 with advanced phones. It replaces option 176.

hth

MS

thanks for your reply. I had not seen that configuration previously.

are you aware of cases that do work with dhcp autoconfig even if your case does not?

Hi,

I guess the 'auto config' works with 'VPN' enabled phones. Not with regular phones. Find the 'administration guide' for the phones you use, it should have all the necessary information on 'dhcp' options.

Hth

MS

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