[Asterisk-Users] port number keeps changing

[Matt Lawson]

We have an asterisk installation that's on a residential-grade DSL and 
its port number (as visible from the outside) keeps changing, every time 
it registers.  fuser indicates that asterisk is only using port 4569 for 
IAX2 (as it should), but when it goes out over the Internet, the port 
number is reported as something in the 10000's and it changes every time.

Obviously, this is a network issue of some type, but can anyone explain 
more precisely why this happens and how to stop it?  We have some other 
installations that stay put on port 4569 like they're supposed to. 
 Network issues aren't my area of expertise.

Thanks.