Execute a command after connecting or disconnecting?

[Bill C Riemers <briemers redhat com>]

Is there a way to automatically execute a command after opening or
closing a connection?

What I would like to do is figure out a way to run "service dnsmasq
restart" when connecting or disconnecting from openvpn.   That way my
dns will not continue to cache lookups across this action.

Currently I do this manually.   Otherwise, if for example I try to open
e-mail when not connected to work, a DNS entry to opendns will be cached
by dnsmasq, even after I am connected via vpn.


Bill