Redundant network paths

We have two sites and two connections between the sites. Theyre both
unreliable (directional wireless).

I'm trying to make them redundant so packet loss is minimum. Something
like Etherchannel will be great, but the connections are at layer 3, no
switch functionality. So we get two IP addresses on each site to use as
gateways.

I've heard of using two static routes with the same metric, but linux
gets hung up on one route (the last one). RIP has a nasty timeout, so
maybe an OSPF implementation can help.

If no downtime at all is impossible, I'll accept upto half a second of
disconnection until the router starts routing through the other route.
What can I do to use two routes redundantly as reliably as possible? If
I cant do it in Linux, I'm open to openbsd and cisco 2500 routers.

Ghazan Haider wrote:

> We have two sites and two connections between the sites. They're both
> unreliable (directional wireless).
>
> I'm trying to make them redundant so packet loss is minimum. Something
> like Etherchannel will be great, but the connections are at layer 3, no
> switch functionality. So we get two IP addresses on each site to use as
> gateways.

Have you investigated bonding in active-backup mode?
http://prdownloads.sourceforge.net/b...g.txt?download
(I've never used it.)

Bonding looks conspicuously like Etherchannel in software, on layer 2.
The problem is I have dual IP interfaces on layer 3, each connection
gives me an IP address to use as gateway. I wonder if I can have a
Linux machine with 4 network cards, routing goes through pairs of
cards, and two cards towards our network are 'bonded'. But this would
really work if it was the ethernet connection at layer 1 or 2 that went
down, since packets would then be sent to the other connection. The
layer 1/2 ethernet connection will not go down since its the connection
between the nodes that will go down. The only notification is route not
found, or route not available or something similar on layer3.

I'll keep reading it to check if it can do layer3. I think the VRRPd2
was made specifically because theres nothing in Linux for layer3 (maybe
a fancy zebra OSPF setup). VRRP has terrible recovery times (90
seconds), CARP sounds much better, but I'm still fishing.

Ghazan Haider wrote:
> Bonding looks conspicuously like Etherchannel in software, on layer 2.
> The problem is I have dual IP interfaces on layer 3, each connection
> gives me an IP address to use as gateway. I wonder if I can have a
> Linux machine with 4 network cards, routing goes through pairs of
> cards, and two cards towards our network are 'bonded'. But this would
> really work if it was the ethernet connection at layer 1 or 2 that went
> down, since packets would then be sent to the other connection. The
> layer 1/2 ethernet connection will not go down since its the connection
> between the nodes that will go down. The only notification is route not
> found, or route not available or something similar on layer3.
>
> I'll keep reading it to check if it can do layer3. I think the VRRPd2
> was made specifically because theres nothing in Linux for layer3 (maybe
> a fancy zebra OSPF setup). VRRP has terrible recovery times (90
> seconds), CARP sounds much better, but I'm still fishing.

The Linux Advanced Routing & Traffic Control site might provide
some useful information?

http://lartc.org/

iproute2 can be used to configure multipath routes, but, again,
I've never used them.

http://lartc.org/manpages/ip.txt
http://www.policyrouting.org/iproute2.doc.html

Regards.