It can be even more tricky - if you use standard signaling/RAS ports, some routers work as an ALG (Application Level Gateway) for H.323 and mess up with signaling/RAS messages. The most funny thing is that "feature" is usually not documented at all in many such routers.
----- Original Message ----- From: "Siderite" <Siderite@xxxxx>
Sent: Saturday, January 29, 2005 12:36 PM
For a few days now I am bombarding Michal with questions regarding the failure of about 1 call out of 3 in a setup like this: Gw1->CiscoGk->GnuGK->Gw2
Of course, it was not his fault, but mine, or rather my IP setup. You see, the setup is more linke this:
Gw1->AR450 router->CiscoGk->Ar450 router->GnuGK->AR450 router->Gw2
And the router had a firewall! Now, the firewall is correctly configured, all the IPs in this setup are configured as trusted and all traffic from and to them is untouched (or should not be touched) by the firewall.
By disabling the firewall the failure did not occur again.
I am posting this so that other don't bump into it and not know what to do. This is how the problem looks like:
In a call LRQ/LCF are exchanged, then CiscoGK is trying to connect to GnuGK to channel the call. In some of the cases, the connection is not established. What appears in the GnuGK logs is only LRQ/LCF and then nothing. The call is not even logged. What appears in the detailed TCP dumps is that a connection tried to be established (in the normal three-way-handshake) but the third ACK packet is malformed and the connection is reset. A RST with sequence number 0 is issued from the GnuGK computer.
The computer is running GnuGK 2.2.1 and Slackware 10. The router is AR450 by Allied Telesyn GW1 and CiscoGk are Cisco. GW2 I don't know what it is and it doesn't matter, as the call never goes through in a bad scenario.
Phew :( Now I am getting a lot of 34,3,17,41 errors in the calls, but at least the calls are being logged and I can move on.
Thanks Michal for being so helpful!
-- Siderite <Siderite@xxxxx>
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