[asterisk-users] strange cisco nat issue

[JR Richardson]

Hi All,

I'm running into a reoccurring nat issue, phones (Linksys, Polycom or
Cisco) behind a cisco router, 2600 series, ios 12.4.  Sometimes 2 or
more phones will have the same outside port number and will register
to Asterisk with the same port number.  As far as I can tell this is
only occurring with the SIP port, not RTP ports.

To resolve, I have to go into the router and clear the translations
for one if the phones, restart the phone and it nails up a new nat
session on a different outside port in the router.  This seems to
happen more often after some power failure on site, when many phones
reboot at the same time.

This has happened various times at different customers, large and
small, different phones, different Asterisk servers.  The only thing
common in all cases is the cisco routers.  We have tried different IOS
releases as well.  So I'm pretty certain this is an Cisco IOS bug or
maybe a router overload?  I've searched for a cisco nat bug with no
luck.

So my question is, has anyone else experienced this type of issue and
if so, is there a solution to resolve?

Thanks.

JR
-- 
JR Richardson
Engineering for the Masses