CirrusHi All,
This is a standard behavior of F5 where there is an already existing server side connection with port 5060 associated with the another client. Then for the new client the NATTED port will be always random.
ClientA:
1.2.3.4:5060 --> 1.1.2.1:5060
1.1.1.1:5060 --> 1.1.3.1:5060
ClientB:
4.3.2.1:5060 --> 1.1.2.1:5060
1.1.1.1:23010 --> 1.1.3.1:5060
Irrespective of these change in port there should not be any issue in message routing back to client from F5.
Since the server side connection mapping with source port 5060 is already used by ClientA any other client that comes later will be assigned the natted port randomly so that F5 can able to route the request back to the correct client based on connection mapping.
If there are requirements to use always source port 5060 with the server it is not possible with just plain configuration we need a combination of following
1) SIP one connect profile similar to http one connect(* conditions apply)
a) N no of client side connection entry
b) A pool of server side connection
2) SIP session persistence based on unique values likes callid, ClientIP:Port etc
3) iRule to route message from server to client based on SIP persistence records.
You can look something called as Message Routing function in 11.6.0 if that solves the purpose.
-- Syed Nazir