FreeBSD network failover

[Randy Bush]

>>> I have a nat'd box which obviously has an internal and external ip
>>> address. The box has a third interface which is configured to a
>>> DSL connection. My goal is for that interface to be activated if
>>> the external side fails so that outbound traffic still flows. Any
>>> of you know of a way to accomplish this regardless of the type of
>>> failure.
 >> what routing protocols are involved?
> Its just IP and nat and there is an IPSec tunnel in place. I need to
> know that if the ISP goes out the DSL connection will be able to do
> certain things, like say sending an email to a pager letting us know
> that the main connection went down.

freebsd does not allow metrics on static routes, which would be the 
'normal' hack.  i.e. you can not have two default routes with different 
weights.

so you may be left with a scripted hack which pings, or otherwise 
checks, the next hops of the two exits and adds/deletes default routes 
appropriately.

randy