NAT Problem with SIP Connections on 878

Unanswered Question
Jan 8th, 2009


we are using SIP to connect SIP phones to a SIP solution in our datacenter. The connections are build with Cisco 878 routers. We are making NAT on these routers.

We are using the following software:


Sometimes calls are not be established. I can see the following to NAT entrys for one source port:

sh ip nat trans

udp x.x.x.y:5005 x.x.x.x:10001 x.x.x.x:10001

udp x.x.x.y:5005 x.x.x.x:10057 x.x.x.x:10057

udp x.x.x.y:1050 x.x.x.x:5060 x.x.x.x:5060

udp x.x.x.y:1054 x.x.x.x:10184 x.x.x.x:10184

udp x.x.x.y:1055 x.x.x.x:10185 x.x.x.x:10185

udp x.x.x.y:1053 x.x.x.x:5060 x.x.x.x:5060

If these two nat entrys for one source port and IP combination the call can not be build up.

Did somebody had the same problem?

Is that a software problem?

Thanks and best regards,


I have this problem too.
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