[LARTC] Redundant Internet connections

["Seth J. Blank" <sblank@cms-forex.com>]

I have a firewall with two redundant internet connections coming in 
(eth0 and eth1) and an intranet behind eth2.

What I am trying to do is have data off of eth2 split evenly between 
eth0 and eth1, and if one interface goes down, to fully utilize the other.

What I'm trying to do is have all data from eth0 be passed on to eth2 
(unless it's stopped by the firewall), same with eth1, and all data from 
eth2 be split evenly between eth0 and eth1.

currently I have the following routes and rules to accomplish this:

ip route add 10.0.0.0/8 via GATEWAY0 table 1 proto static
ip route add 10.0.0.0/8 via GATEWAY1 table 2 proto static

ip route add default table default scope global nexthop via GATEWAY0 dev 
eth0 weight 1 nexthop via GATEWAY1 dev eth1 weight 1

ip rule add pref 1500 iif eth0 table 1
ip rule add pref 1501 iif eth1 table 2
ip rule add pref 100 iif eth2 table default

This does NOT work properly.
 From localhost, everything works perfectly. I can bring up and down 
interfaces and everything works properly and transparently.
But, from the intranet, everything stops. With a different default route:
ip route add default via GATEWAY0 dev eth0 table default
everything is fine from both localhost and the intranet. Same with 
GATEWAY1 eth1.

Can anyone offer advice on how to resolve this problem?
The only way I can think of so far is a remarkably simple but stupid 
hack, where I just ping -I eth0 GATEWAY0 and ping -I eth1 GATEWAY1 every 
thirty seconds or so and switch default routes if an interface is down. 
This obviously does not solve the problem, nor allow bandwidth to be 
shared across both lines.

Any help would be greatly appreciated.

Seth J. Blank
Systems Operations
Capital Market Services, LLC



_______________________________________________
LARTC mailing list / LARTC@mailman.ds9a.nl
http://mailman.ds9a.nl/mailman/listinfo/lartc HOWTO: http://lartc.org/