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How to routing SIP/RTP traffic from PBX to a specific router

Hi all this is my first post hope posting on the right group, if not please let me know.


We recently installed a new data line and now all traffic are going out through the new line. The problem is that we have a Panasonic PBX on that remote site with SIP Trunk associated to other data line from another ISP. Since the changes our SIP Trunk on the PBX can no longer authenticate so, it's down. The PBX still working but via ISDN.

Due to complicated reasons I can't move the SIP Trunk to the new data line.

I asked the ISP who owns the SIP Trunk for solutions and they said I only need to forward all SIP/RTP traffic to their modem/router.


Well, I don't know how to do it.


How can I forward only SIP and RTP traffic to the SIP Trunk modem?

Can you guys help? I really appreciate your help here.


See PDF attached with the topology.


Many Thanks,

Everyone's tags (1)

Based on your visio you would

Based on your visio you would point the sip trunk on the panasonic PBX to the providers sip trunk address and just make sure your routers are setup to route(static route maybe?) to the correct Modem.


Hi Shawnlund,Thanks for your

Hi Shawnlund,

Thanks for your reply. All configurations on the PBX are correct, it was working fine before we route all traffic through other ISP router.

- The only traffic that need to be send to the SIP Trunk modem is SIP and RTP traffic. Everything else should follow the normal path through ISP1 router.

- SIP Trunk modem/router is locked by ISP2 and only allow voice traffic. So I can't remote to the PBX through ISP2.

- How can I identify SIP/RTP traffic coming from the PBX and reroute them to the SIP Trunk modem/router?


VIP Advisor

Hi, Looks to be a routing



Looks to be a routing problem more than IP telephony. On your edge router which route the traffic to both ISPs (I think it is 1941) you need to configure policy-based routing (PBR) and apply it on the ingress interface which is facing your LAN.


ip access-list name Match-VoIP-Traffic

per udp any any rang 16384 32767

per udp any rang 16384 32767 any

per udp any any eq 5060

per tcp any any eq 5060

per udp any eq 5060 any

per tcp any eq 5060 any

per udp any any eq 5061

per tcp any any eq 5061

per udp any eq 5061 any

per tcp any eq 5061 any


route-map permit Route-VoIP-Traffic

match ip address Match-VoIP-Traffic

set ip next-hop ***SIP ISP Gateway IP Address***



ip policy route-map Route-VoIP-Traffic


Hi Mohammed Al Baqari, Many

Hi Mohammed Al Baqari,


Many Thanks for your post, I will try the PBR as you mentioned ASAP and let you know the outcome. The funny thing is that today I started to read Route Maps and Policying-Based Routing to see if it could help me with this problem. :)



Hi Mohammed Al Baqari, When

Hi Mohammed Al Baqari,


When you say

set ip next-hop ***SIP ISP Gateway IP Address***

are you refering to the Gateway of the ISP 2 SIP Trunk Modem?

I applied the PBR on the ingress interface of my 1941 router and I can see the matches with show route-map command but my SIP Trunk still not able to register.

I want to make sure all configurations from my side are correct before I complain to ISP 2.



VIP Advisor

Hi, I don't understand your

Hi, I don't understand your topology to confirm your gateway. This should be the which is sending to ISP2.


In you access-list try to include CUCM IP address to any and then try to ping your SIP modem and see if reachable.


Hi Mohammed Al Baqari,the

Hi Mohammed Al Baqari,

the next-hop was correct but I'm affraid the problem I have is related with the Provider which I already raised a ticket with it. Let see what they say.


Hi Mohammed Al Baqari,I founf

Hi Mohammed Al Baqari,

I founf the source of the problem, no need for the PBR implementation.

A while ago we maed a change on R2 which included shuting down VLAN 1 and creating a transit VLAN99. Unfortunately we didn't include that VLAN on the NAT. The traffic was going in one direction only. Also the PBX settings had to be changed.


Thank you all for your help and support.

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