[asterisk-users] Strange asterisk message "Remote host can't match request NOTIFY..."

[Bruce Komito]

For some time, I've been getting the following messages continuously from
one of the LANs that I have a number of phones on:

[Nov 10 10:09:51] WARNING[32945]: chan_sip.c:12543 handle_response: Remote host can't match request NOTIFY to call '6da3b2c278c4e3d067c0cbe801097a32 at 216.162.162.37'. Giving up.

Although the message doesn't specifically mention a SIP extension by name,
I have determined these messages are coming from a number of ZIP2 phones
attempting to subscribe to message waiting service.  One reason I'm
pretty sure about this is that the MWI light on the ZIP2s doesn't light
when it should.

The phones are connected behind a Cisco router running NAT.  I have other
ZIP2 phones on other networks that do not have this problem, and I have
other non-ZIP2 phones on this network that also do not have this problem.
As a result, I have concluded that it is some combination of factors
having to do with the ZIP2 AND Cisco NAT together, but beyond that, I
haven't a clue.

Has anyone ever seen a message like this, and/or understand the cause and,
better yet, the solution?

TIA!

Bruce Komito
WPTI Telecom
775-236-5815