Jan Janak writes:
The gateway should check if the request is coming
from the IP and port
of the trusted proxy server and in addition to that it should verify
that the Request-URI contains the IP (not hostname) and port that belongs
to the gateway.
just to let people know, cisco ios gws do NOT check host part of
request-uri belongs to itself and thus happily process any invite they
receive. as far as i know, there is currently no way to configure such
a check in ios gws.
-- juha