Multitenant Setup Does not Support Multiple Generic P2P SIP Trunks from Same Provider if Provider IP is Same

[bmwaura]

I am managing a multitenant V20 deployment that requires mapping multiple peer-to-peer SIP trunks to the same Provider IP.

To maintain isolation, we have implemented 802.1Q subinterfaces at the OS level to ensure traffic for each tenant/trunk enters the server on a distinct VLAN. While routing at the network layer is correctly partitioned—verified by successfully sourcing pings from the respective subinterfaces—3CX is failing to differentiate the trunks at the application level. Because the Provider IP is identical for all trunks, 3CX ignores the VLAN ingress and defaults to the first configured trunk in the list, effectively hijacking the traffic.

Since 3CX does not natively support binding a trunk object to a specific local interface, we are hitting an application-layer limitation where the PBX is blind to our VLAN-based separation.

Is there any way in a multitenant V20 environment to force a peer-to-peer trunk to associate its identity with the specific local interface or subinterface where the INVITE was received?

 

[KyriacosS_3CX]

Hello, does DID assignment to each trunk not isolate them per tennant for you? Still in general for Multi-Tennant, IP based trunks are not optimal. Are you exiting your network towards the Trunk provider using multiple public IPs?

 

[YiannisH_3CX]

Did you use the Generic template to create all trunks? If so you will need to disable the call source identification settings from ALL trunks given the DIDs are unique for each trunk.