There are two places where one is prompted for TRUNK NAME.
First in setting up a trunk, and again in inbound routing.
However I believe that these to are not necessarily the same. on the inbound routing it appears to refer to the DNIS of the inbound call. In trunk name it can be indpendent of the inbound call completely.
At the trunk name prompt in the trunks section you give names to trunks. Let's say a, b and c.
Now in inbound routing you can limit your route to calls coming from specific trunks. E.g. if you enter a here, the route will be valid for calls from trunk a only. We could have made a selector box in inbound routing.
You can also write addresses you want to be reached at from outside into the trunk name of inbound routes. E.g. supernettel-sales then the route would be valid for people calling the SIP URI supernettel-sales@pbx.i-p-tel.com (or supernettel-sales@217.195.32.11 til the nameserver is setup correctly).