[Asterisk-Users] NAT table expiration

[Manuel Wenger]

I'm having a problem with some customers sitting behind "hopefully SIP aware" routers doing NAT. These routers translate port 5060 to something different (ie. 10001) in order to be able to connect more than one SIP client on a single NATted LAN.

Unfortunately, after a while the router seems to "forget" the NAT table, ie. which port belongs to which SIP client on the LAN. This happens with different router brands (Alcatel, Zyxel).

Maybe the expiration is set too long? Is there a common standard or a maximum recommended value for these situations? I think 60 minutes is definitely too much, 5 minutes is too short... is there a better way than "trial and error" to find out a good value for this?

Another question: in a "sip show peer" screen i see the following values

  Expire       : 27345
  Expiry       : 900

What's the difference between them?

Furthermore: if the client supports STUN or other NAT traversal methods, do I need to use them, or will Asterisk take care of everything? We always have Asterisk in the media path, so clients never talk to each other directly.

Thanks
-Manuel


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