My connection to the Internet is via Aussie Broadband and the Australian National Broadband Network. Ostensibly it's a dynamic address, but in practice it almost never changes. I have built some of my infrastructure relying on that.

When things do change (mercifully less than once a year), it requires a certain amount of reconfiguration. Here's what I need to do, based on my experience of 22 November 2018:

1. In /etc/rc.ipfw (my simplified version of /etc/rc.firewall), change the gateway IP address:

   -GW=180.150.113.90
   +GW=100.64.51.240
   

2. Stop natd.

3. Reload firewall rules.

4. Restart natd:

   natd -p 8668 -n xl0

   I think that this is necessary to ensure that things work correctly.

5. Update my DNS configuration. For reasons that I forget, but which are important, I have my local web server listening on the external interface, and that had changed:

   -aussie-gw              IN A            180.150.113.90  ; gateway to Aussie Broadband
   +aussie-gw              IN A            100.64.51.240   ; gateway to Aussie Broadband
   

6. In ~grog/public_html/php/header.php, change the local server address to be able to recognize local access:

    $islocal = preg_match (":192\.109\.197\.[0-9]:", $_SERVER ["REMOTE_ADDR"])
   -  || ($_SERVER ["REMOTE_ADDR"] == "180.150.113.90");
   +  || ($_SERVER ["REMOTE_ADDR"] == "100.64.51.240");
   

7. Update ~/bin/linkcheck to show the new remote end of the link:

    # This should be the other end of the NBN link
   -NEXTHOP=180.150.112.1
   +NEXTHOP=100.64.32.1
   

8. On remote systems, update squid) /usr/local/etc/squid/squid.conf and restart amazingly slowly:

   -acl radiation_tower src 180.150.113.90 # Aussie BB gateway
   +acl radiation_tower src 119.17.139.240 # Aussie BB gateway