redundant default routes?

I have a bunch of system that are on a private single-segment network.
They currently use a Linux box for a default gateway to company
network (GW A). I have another Linux box that has one NIC in the
private net and the other in the corporate (GW B). I would like a
host on the private side (client) to use host A for a gateway unless A
is not available, then use B. The client only has one NIC so I
couldn't figure out how to use multipathing. The clients are all
Linux boxes as well. How can I get the behaviour I would like.

+-------- corpnet --------+ 10.111.3.x
| |
| |
+------+------+ +------+------+
| GW A | | GW B |
+------+------+ +------+------+
| |
| |
+-------- privatenet------+
|
|
client 192.168.x.x

Thanks to anyone who has a solution.
Jay M.
Redmond, WA (and using Linux)


Jay McCanta

(E-Mail Removed) (Jay McCanta) writes:

>I would like a host on the private side (client) to use host A for a gateway
>unless A is not available, then use B.

>The client only has one NIC so I couldn't figure out how to use multipathing.
>The clients are all Linux boxes as well. How can I get the behaviour I would
>like.

One solution would be to use a routing daemon like quagga, but it's probably
a bit messy having to install that on every client.

A better idea would be to use something like VRRP (Virtual Redundency Router
protocol), where the IP address used as your default gateway will shift from
one gateway to the other, should the primary fail.

I've not played with VRRP under Linux yet, so I can't give any advice as
to the feasibility of this (but I've done enough HSRP on Cisco routers
to know the concept works).

Maybe you'll find this of interest: http://www.keepalived.org/

Cheers,

Paul.

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