Sip peer trunk not working




The situation is there are two sites which using UCM6510 pabx where i named it as site A (KPC) and site B (NDWT). The problem is Site A can peer with site B but site B cannot peer with site A. After hundreds of time checking, there is no differences in term of config between site A and site B. The funny things is site B can ping and tracert to the site A.

Is there any suggestion or recommendation for troubleshooting?


Catch packets on both UCM and see if packet receive to destination, and if yes why it is rejected (code).


Also look for the IP seen and used by each site to communicate with the other. Look in the contact and connect headers.


I believe you should also make sure you’ve got the external IP address configured in each device.

PBX Settings -> SIP Settings -> NAT -> External Host.



After several times doing troubleshooting, i’ve just discover that the problem occurs related to load balance masquerade configuration on firewall (mikrotik brand). The masquerade configuration need to be disabled and ip route need to be added.