One of our customer has two office branch in different cities and two MSS have been deployed. Following figure describe the network topology:
The extensions of MSS1 are 1xx, such as 100,101, and so on.
The extensions of MSS2 are 2xx, such as 200, 201, and so on.
With previous MSS versions, it is no problem to send/receive instant messages between local users. But it cannot send instant messages to the extensions of another SIP server.
So we upgrade MSS to V6.1.5 to support instant messages between SIP servers.
To do that, we need establish SIP trunk between these SIP servers. Once you can make calls to the extensions of another SIP server (MSS), it will be no problem to send instant messages to them.
That means we need configure MSS with (1) peer server configurations, (2) Dial plan configurations which we have described in “how to use SIP trunk” document. Please refer to following document for details of SIP trunk: