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Right, this might be a long one, so bare with me...

I have 2 machines, lets call them local1 and cloud1. local1 has 3 Nics: 2 connected directly to cable modems with public IPS (call them eth0 and eth1) and 1 connected to my LAN connection (eth2). cloud1 has a single nic (eth0) and is connected directly to the internet (1Gb/s link in a datacenter). eth0 and eth1 on local both have default gateways and send their traffic over either, depending on which IP is making the request. There are 2 OpenVPN P2P tunnels created, each using one of the public IPs from the modems, and connect to cloud1 over its public ip. This creates 2 tunnels, tun0 and tun1 on each box. they get ips 10.8.0.1/2 on tun0 (respectively) and 3/4 on tun1. 1 and 3 are on cloud, 2 and 4 are local.

the local box has its default route set to use both 1 and 3 (Debian 8.3 with whatever kernel is in the box) and that works "correctly" trace route shows me hitting both 1 and 3 at different times). but on cloud1, for it to get back to my local network (192.168.1.0/24) it has a route, but only through 10.8.0.2... nothing comes back over 10.8.0.4...

watching traffic monitors, i can see traffic going out over tun1 in house, but nothing (or very little) coming back in, while tun0 has lots of traffic coming both in and out...

So, after all that, the question: I know how to set multiple default gateways using linux, but how do i set multiple non default gateways: for example:

ip route add 192.168.1.0/24 via 10.8.0.2 (works)
ip route add 192.168.1.0/24 via 10.8.0.4 (tells me it already exists)

Network forwarding is set on both boxes and i would like to do this without NAT or Masquerading... Also, 192.168.1.0/24 is a DMZ Network, so there are further upstream firewalls for other machines...

Thanks.

  • I think that's not possible as, although you call it gateway, you are setting up static routes. – sysfiend May 24 '16 at 7:02
  • @Alex yea, its a static route, but the end point would be a gateway, right? I have been looking to see if BGP or ECMP would work, but though this might be the easier option... might be wrong... – TiernanO May 24 '16 at 7:17
  • I wouldn't call it gateway as gateway is used make reference to a route where to go when you don't know how to get to other network. – sysfiend May 24 '16 at 7:56
  • @Alex that box doesn't know how to get to the other network: its got a public ip (37.x.y.z) and has 2 tuns to 10.8.0.0/24... for it to get to 192.168.1.0/24, it needs to use 10.8.0.2 or 10.8.0.4... currently it uses just 2... that sounds like the definition of a gateway to me... – TiernanO May 24 '16 at 8:26
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So, for anyone reading, i have managed to solve this. Zebra's Static Routes which allows me to have 2 routes for the one subnet. I had to remove the original route on the cloud box, and then zebra took over and all traffic is sent between those 2, equally... happy days!

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