[asterisk-users] Cisco 7970 behind NAT

Jeremiah Millay jeremiah at rockriver.net
Thu Sep 21 07:18:55 MST 2006

Shortly after I sent this e-mail I got it figured out. In sip.conf I had 
to put nat=no. The phone config also need to have all NAT features 
turned off. It was strange because I was sniffing the packets for the 
registration and saw no authentication information coming from the phone 
(with a really high source port number I might add), then I turned off 
NAT in sip.conf and did a reload and all of a sudden the phone was 
registered. This is the opposite of what I do for my 7960s running the 
7.4 SIP image.
After I got the 7970 working I had a 7961 running the 8.0.2SR1 unified 
image and had to do the same thing. The config files and settings for 
phones running the newer Cisco SIP software all require these 
parameters. Just an F.Y.I.

> The problem is that the 7970 phones by default are listening for replies
> to their register requests on port 5060.  Unfortunately, the phone sends
> them out from random ports.  So, if you have nat=yes on the sip peer in
> asterisk then the asterisk will send the reply to the port the request
> came from and not 5060.
> The only deployment we have done of these phones with NAT involved was
> for 2 executives at a branch office.  In order to get the phones working
> we had to set the XML configs for the phones to send the external IP
> address of the firewall (you'll need a static IP for this to work) and
> to request replies on a custom port other than 5060.  We then gave the
> phones DHCP reservations so they would always get the same private IP
> and mapped the custom sip ports through the firewall to each of the 2
> phones.  The sip peers in asterisk then had nat=no.  Kind of a kludge
> but since there were only two 7970 phones it was manageable.  The other
> cisco phones don't seem to have this problem.
> Perhaps somebody out there knows a way to make the 7970 phones accept
> SIP responses back to the originating port.  I wasted several hours but
> couldn't figure it out.
> -Evan

Rock River Internet                            Jeremiah Millay
202 W. State St, 8th Floor              jeremiah at rockriver.net
Rockford, IL 61101                      815-968-9888 Ext. 2202
USA                                               fax 968-6888

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