Re: Re: [LARTC] multipath routing problem [Shorter version] - Help

[Julian Anastasov <ja@ssi.bg>]

	Hello,

On 29 Oct 2002, Vincent Jaussaud wrote:

> I was thinking about using the metric value for this.
>
> Let's say:
>
> ip route add table dual-gw proto static 192.168.0.0/24 via GW1 dev eth1
> metric 1
> ip route add table dual-gw proto static 192.168.0.0/24 via GW2 dev eth1
> metric 2

	No, the metrics work only if the routes disappear.
This usually happens when device goes down (for example, ppp).
For gateways reachable via ARP it can't work.

	You need to define alternative routes (ip route append), see
my docs about alt routes that use same metric.

> I assume the kernel will always use the best route, that is the one with
> best metric. So that all packets will use the same route.
> If GW1 breaks, patched kernel should mark first route as dead, and force
> all further packets to use GW2 instead.

	No, dead gateway detection currently works for routes with
same metric. But even then the detection is passive and needs help
from user space. Without such checks you can expect almost random
results. OTOH, you can run your own checks and to keep only the
alive routes.

Regards

--
Julian Anastasov <ja@ssi.bg>

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