[ILUG] Routing question

[Niall O Broin]

On Mon, May 20, 2002 at 05:02:22PM +0100, Thomas Bridge wrote:

> >I manage an office which has an Internet connection via a leased line.
> >However, bandwidth on this line is somewhat expensive. I'm planning to
> >install a DSL line (so obviously, the office isn't in Ireland :-( ) and use
> >that for most of the outgoing traffic. But how best to do it ? Can I add two
> >default routes to the clients, the route through the DSL machine having a
> >lower metric than that through the leased line ? Or should I make all the
> >clients have a default router to the DSL box, and then have that box's
> >default route be through the DSL connection except when the DSL is not
> >available for whatever reason, in which case it would route via the box on
> >the leased line. As I am doing NAT on the current firewall (connected to
> >the leased line) and I'll be doing NAT on the DSL box is that likely to
> >cause me some confusion ?
> 
> I'm already confused :)
> 
> If have this right, you want the traffice to go out over the DSL except if 
> it goes down at which point you want to go it over the leased line.

That's right.

> Are you planning to use the same set of IP addresses regardless of which 
> link?   Or does the source IP address of the traffic depend on which 
> interface the traffic is NAT'd through?

I don't much mind - as it's all NAT'd traffic anyway, I really don't care
with what source address it goes out. And I'm not concerned about failouver
- if the DSL goes down, and an existing connection is lost, so be it.
Certainly wouldn't be worth trying to do anything else. I'm open to how to
physically implement this too - whether to add another NIC to the existing
firewall and connect that to the DSL box (AFAIK it's PPPoE) or to use a
separate box. (I could tell you that the DSL line is an ISDN + DSL line and
that we're going to use the ISDN part for yet another route but as it's not
germane to the discussion, I won't :-) (it's for a point to point link))




Niall