Registering IP phone with NATeD IP address of Call Manager Ver. 6.0

Unanswered Question
Sep 25th, 2009


I have Cisco Call Manager version 6.0 running, in 'inside' zone of ASA 5520 Firewall, in my network. I'm trying to register Cisco IP phone connected in DMZ zone with CUCM running in inside zone.

To achieve CUCM connectivity, have configured static NAT in Cisco Firewall.

After this i observed IP phone got connected to CUCM and also able to download upgrade image, but it fails to register to CUCM.

Further to this IP phone show perfered CM as orginal IP address of CUCM, that not the NATed IP address. This could be because of XML file which IP phone has got from CUCM.

My Question:

1) Do NAT won't work with CUCM??

2) Is there any wayout to edit XML file, so that perfered CM could alter?

Please let me know!



I have this problem too.
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chrward Fri, 09/25/2009 - 09:03

The reason the phone is looking for the non-NAT'd CUCM IP address is because the firewall is not inspecting the TFTP traffic that is used to send the config to the phone from CUCM. The XML file contains these IP addresses. You can either see if there is a TFTP inspect you can run on the firewall to rewrite this, or use DNS names instead which a DNS server outside you NAT could use to resolve to the NAT'd IP.

Also, I think the officially supported method to accomplish what you are trying here is the PhoneProxy feature set on the ASA.



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