Crazy thing: No dialtone from a SPA 3102 inside the same network.

Question

Hi folks: We have a couple of SPA-3102 connected to two POTS Bellsouth lines. Both 3102 are registering fine with our SIP server and also register the phone line.
The crazy thing is this: If we try to get dialtone calling from an IP phone (SPA922) LOCATED IN THE SAME LOCAL NETWORK (I.E: In the office) to the 3102 number, we get no dialtone.
If i try co call the same 3102 from a softphone (x-lite) also in the office, we still get no dialtone.
But if i try to call the spa from other network than the office, (I.e: My home), i´m getting the dialtone!!!  I tried it with both the 922 IP Phone and the x-lite softphone and works fine.
Also, we tried to call the 3102 from other IP phone in our office in Mexico, and also works fine.
Our network topology in the office:  Motorola´s Netopia 3347-02 with Bellsouth xDSL internet service. Two Linksys EZXS16W swithes, and a mix of laptops, PCs, servers, IPPhones (SPA922 and 942) and printers connected to these switches
Any idea ??
Thanks in advance.
Martin

Answer 1

If the in-office X-Lite is accessing the SPA-3102 on its private IP, try the public IP, or vice-versa.
I'm presuming that the SPA-3102 has a static private address, the Netopia is forwarding some UDP ports to the 3102, and that you are accessing the 3102 directly (not through a server such as Asterisk).  In this case, access from the LAN via the public IP may fail, because many routers don't handle 'hairpinning' correctly.  Access via the private IP may fail, because the client is being confused by the NAT mapping being applied by the 3102.  You can use Wireshark on the machine running X-Lite to see what's happening in each case.
If your situation is other than the above, please provide the details:  Accessed via server?  If so, is server on LAN or outside?  What software?  Do you have administrative control over it?  Does your router have a SIP ALG?  Is it being used in this path?  What port forwarding or other special setup on router?  What NAT mapping parameters on SPA-3102?  What have you seen with Wireshark?  What remedial actions have you tried, with what results?  Do you have multiple static public IPs?  If so, is there a spare one?
Message Edited by Stew on 05-05-2008 10:48 AM