08-26-2013 07:01 AM - last edited on 03-25-2019 03:39 PM by ciscomoderator
Good morning.
I have following example schema
SIP PHONE -> CISCO 887 -> SIP GATEWAY
1) SIP phone register on SIP gateway and send
REGISTER sip:sip.gateway.com SIP/2.0
Via: SIP/2.0/UDP 10.111.111.6:5060;branch=z9hG4bK-t8pe125htptd;rport
......
2) Everything fine but after packet pass through NAT on Cisco 887 it look like
REGISTER sip:sip.gateway.com SIP/2.0
Via: SIP/2.0/UDP 2.2.2.2:1025;branch=z9hG4bK-t8pe125htptd;rport
.......
but packet itself go from port 1024
Due to it gateway register PHONE in accordance with field VIA and port 1025 and all incoming calls to phone go to port 1025
which never reach phone.
3) looking on nat table
udp 2.2.2.2:1024 10.111.111.6:5060 sip.gateway.com:5060 sip.gateway.com:5060
udp 2.2.2.2:1025 10.111.111.6:5060 sip.gateway.com:5061 sip.gateway.com:5061
udp 2.2.2.2:1025 10.111.111.6:5060 sip.gateway.com:5060 sip.gateway.com:5060
Is it possible to do something to force Cisco router not to do this mess ? I.e not to change port number in VIA header.
08-27-2013 07:04 PM
Hmmmm ... I've seen something like this. Particularly when you run SIP firmwre 9.X. Downgrade your phone's firmware to 8.X.
08-28-2013 12:52 AM
Thanks for answer. But it is not related to phones.
It is more related that broken sip alg in lastest version of IOS 15.3
08-28-2013 04:10 PM
Thanks for answer. But it is not related to phones.
It is more related that broken sip alg in lastest version of IOS 15.3
Errrr ... I don't think so.
I have, at home, CP-7970 and a 880 router. When I first ran my 7970 with 9.X firmware, it wouldn't register with my Voice SP. When I did "sh ip nat trans | i
Disabled ALG on the router, still no result. Enabled port forwarding, doesn't work.
In the end, I downgraded the 7970 to 8.X firmware and rolled-back the changes I made to the router and everything works.
Now, I've got an Asterisk in a Raspberry Pi with my 7970 and a handful of 7960. Works a treat!
Don't even bother reading this response.
08-28-2013 05:38 PM
Leo, from my understanding, the OP is not using a Cisco phone at all.
08-28-2013 06:50 PM
You're right, Paolo.
Somehow I had the impression he was.
08-29-2013 12:36 AM
Thanks for reply.
Sorry but I am really not undertand why you speak about phones . It is BUG in Cisco ios 15.3
Because when i returned to IOS 15.2 all started to work.
I still trying to find out is it possible to force CISCO SIP NAT ALG to be compatible with RFC 3261.
08-29-2013 04:09 AM
What you should do is to contact the TAC so that the bug in 15.3 can be identified and fixed.
08-29-2013 06:29 AM
Hi. Thanks again for your answer.
Yeah i understand it.
But for me much better to force router to avoid such behavior at all. Because such SIP ALG issues happens not first time. I seen such issue at least couple of IOS versions. In one version it broken, next fixed, after couple of monthes they break it again etc.
08-29-2013 01:15 PM
That is normal with Cisco software.
If you have a version that works, just use it.
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