mark,
lets sat your proxy gets an initial request with pre-loaded route header
Route: <sip:proxy.foo.bar>
assuming that proxy.foo.bar is hostname of the proxy and not any of the
domains that the proxy is responsible for, my understanding is that
alias is the only way to make the proxy to realize that the route
specifies this proxy if your listen lines contain ip addresses.
i'm further assuming (not knowing) that if you add a port to alias, then
the proxy will not consider the route specifying itself if the request
came to another port than the one added to alias.
someone who knows the internals of loose_route function, could tell if
the above is true or not.
-- juha