[Asterisk-Users] How do you handle NAT?

[Matthew Boehm]

We are interested in how other people are handling NAT problems. We have 
several customers all of which have some sort of firewall/NAT device at 
their location. For simplicity sake, all customers' internal networks 
are 192.168.*.*.

Our asterisk box is on public IP not blocked by any FW/NAT.

I use QUALIFY=yes on all our customers' phones and I feel that sending 
out 80-something keep-alive packets is causing our box to crawl and 
cause bad calls.

Would SER be better in this case? Should I have phones register with SER 
instead of with Asterisk?

Thanks,
Matthew

P.S. Yes, I have read stuff on NAT on the wiki. I'm more interested in 
other real world, working, solutions.