asterisk users - Jun 2005 - Strange behaviour with lost internet connection

I have noticed a strange behaviour when our internet connection was
down a couple of hours last week.

What happens is that asterisk starts running *really* slow. If I type
"sip show peers" it sometimes responds correctly and shows all the
connected peers, but sometimes I get an empty list (this seems to go
in cycles). Also the connected polycom phones seems to be unable to
place any calls into asterisk in the same cycles. The phone tries to
initiate a connection to astersk, but gets no response at all.

Other sympthoms are that if I restart asterisk it takes *very* long time
for it to start. (we are talking minutes).

It seems the situation is improved when I remove the "regsiter => "
statements in my sip.conf.

I have tried doing a tcpdump to figure our what is going on but I can
see no packets going in our out during the "stalled" periods.

I am running bristuffed 1.0.6.
Our setup is one external ISDN + a couple of external SIP connections.
Internal ISDN (DECT) + several polycom IP300. Both ISDNs are using
zaphfc.
The intention is that the system should fall back to the ISDN
connection when there is no internet connection, but this sort of puts
a halt to that intention...

Any ideas on where I should start to look are welcome.

/Ola

Problem: 
> It seems the situation is improved when I remove the "regsiter =>
"
> statements in my sip.conf.
Cause:
If your internet connection is down, your DNS isn't working. IF your DNS
isn't working, it won't be able to resolve names. If it can't
resolve a
name, it will sit there trying until it times out.

Solution:
Cache names locally - /etc/hosts, or, just use the IP address in the
register string. Note, this _also_ applies to reverse lookups. Make sure
your DHCP server updates your local x.168.192.in-addr.arpa table so that
_reverse_ lookups work as well.

--Rob