Execute command upon interface initialization?

[Peter Ankerstål]

Ido Admon wrote:
> Hello list,
> I couldn't find any way to execute an arbitrary command upon network
> interface initialization. My situations is that I have and ethernet card
> that takes DHCP from a cables provider (not a fixed IP address) and I
> need to update a DynDNS hostname everytime it does (everytime the IP
> changes).
> I couldn't find a way to execute shell commands using the rc system or
> dhclient, what did I miss?
> Sure I could just use cron but that's not very elegant.

You could use dns/ez-ipupdate. It is a daemon who updates your dyndns 
whenever your ip is changed.