ip refresh, resolv.conf and local scripts on startup?

[Jack Barnett]

I have a script that updates some dynamic DNS records (can be run as
non-root if needed).

It needs to be run on startup - after network is configured and after
rc.firewall (it'll get blocked if it's run before the firewall is setup).

What is a good place to put this?  I could put it at the end of rc.firewall,
but is there a better place to put it?

Also how do I refresh a dynamic IP without rebooting?

Sometimes my cable modem gets messed up and under windows I just do:
ipconfig /release
ipconfig /renew

and it gets new IP and sets everything up.  In FreeBSD is there a way to
reconfigure everything without rebooting?

(rc.firewall uses this to get network info:
        onet=`ifconfig xl0 | grep "inet " | awk '{print $6}'`
        oip=`ifconfig xl0 | grep "inet " | awk '{print $2}'`
Meaning, rc.firewall would also have to be re-ran if the IP is new).
[also to make things more complicated, I think I need a rule in
rc.firewallto allow for DHCP clients to go out?  It gets blocked on
external interface
when firewall comes up??]

Also how do I override /etc/resolv.conf?  DHCP client configures it I think
and sets it up to point to my ISP DNS servers (which suck) and would like to
give it mine instead of there, but it keeps getting over written on startup
when it gets a DHCP lease?

thanks.