Callmanager behind NAT

[defash]

My Callmanager have a private IP that is Natted to a Public IP but my IP communicator at remote site can't work with it. Although the Callmanager IP appears under IP Communicator TFTP device configuration. What can prevent the IP phone at remote sites from working and how do i solve this?

[dgahm]

IP Communicator uses SSCP protocol which embeds addresses in the payload. For this to work your NAT router must have Application Layer Gateway capability. If NAT is performed by a PIX or ASA firewall you need to enable Application Inspection.

Here is a documnet on ALG:

http://www.cisco.com/en/US/products/ps6640/products_white_paper09186a00801af2b9.shtml

Configuring SCCP application inspection in an ASA:

http://www.cisco.com/en/US/products/ps6120/products_configuration_guide_chapter09186a008054c520.html#wp1148989

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