Changed external IP needs to set in sip.conf in Asterisk

[getrav]

I have a Dual WAN setup to ensure we always have Internet Access.

Due to the way Asterisk works, if the external IP address changes, we need to set it in sip.conf.
If you don't then you will not be able to register with your telephone provider.

The setting in sip.conf is known as "externip=x.x.x.x"

What is the best way to get this info from the router?  I know we can use DDNS but this can take up to 10 minutes to update.  Many of the servers have limits to how many times you can poll for an IP update.
You could be loosing business while your users wait for this info to update.

[getrav]

I tried a few things but I am not sure if it will help a lot.
I setup a DynDNS Client and set it to monitor the Gateway instead of a particular gateway.
I changed the cron job every minute:

1    *    *    *    *    root    /usr/bin/nice -n20 /etc/rc.dyndns.update
originally it was 1 hour and 1 minute:
1    1    *    *    *    root    /usr/bin/nice -n20 /etc/rc.dyndns.update

Still, I can't get it to update in 1 minute.  What am I missing?

[phil.davis]

That cron entry starting "1 1" runs at 01:01 each day - only once per day. For every minute you want:
*/1  *  *  *  *  root /usr/bin/nice -n20 /etc/rc.dyndns.update