routing with two ISP's

petterg · Guru Joined: 25 Mar 2004 Posts: 500 Location: Oslo, Norway

To reduce downtime I'm thinking of getting two dsl lines - from two different ISP's. That way, if one of them go down all trafic will be routed to the other one. When both are up they can share the load. (I guess this is called load balancing?)

I have some concerns about this.
With two isp's there will be two IP adresses. If a user on the local network have a open session, say a vpn connection, using webmail, ..., on an remote server - what happens if the load balancer is routing parts of the data in the same session over both connections? The remote server will see two different IP's, right? Will that break the session?

What about running ssh / mail / web servers on this type of connection? Does the servers need to be setup in any particilary way?

I was thinking of letting a gentoo box handle the routing. Is that a bad idea? How would I set it up to make this work?

anjunod · n00b Joined: 03 Jul 2004 Posts: 11

splooge · l33t Joined: 30 Aug 2002 Posts: 636

kashani · Posted: Sat Oct 22, 2005 2:51 pm Post subject:

https://forums.gentoo.org/viewtopic-t-383488-highlight-bgp.html

Here's a fairly lengthy discussion about a similar setup and the issues involved.

kashani
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petterg · Guru Joined: 25 Mar 2004 Posts: 500 Location: Oslo, Norway

So outbound connections wold work fine then? I don't need to wory that vpn and ssh connections will randomly fall down because of the loadbalancing?

For mailserver I guess the incomming routing could be solved by using two MX records?

Outbound connections are the most important.

kashani · Posted: Mon Oct 24, 2005 5:35 pm Post subject:

Yeah for the most part that would work. The only issue might be checking your email. If you hit the IP that's down you don't get in. So you'd have to play DNS roulette till you got the up IP. Chances are this won't happen often so it's not a bad solution.

kashani
_________________
Will personally fix your server in exchange for motorcycle related shop tools in good shape.

petterg · Guru Joined: 25 Mar 2004 Posts: 500 Location: Oslo, Norway

I have some problems with making this outbound routing work.

First I tried this howto
http://lartc.org/howto/lartc.rpdb.multiple-links.html

Then this one:
http://www.ssi.bg/~ja/nano.txt

All other howto's seem to be the same as one of those. Even refering to them.

The problem is that it takes "forever" to switch over from a failed line to the working one. Once it did switch over after about 2 hours. The other times I've tested I've been waiting for 24 hours before giving up. (My way of testing is to unplug one of the network cables.)
Well, outbound connections is the problem. Inbound does actually work! (In the dns record I added two records for the testserver using the same host.domain.tld - one for each of its public ip's.)

Does anyone know of any other way to do loadbalancing / failover for outbound connections? (I'm using 2.6.13 kernel)

midknight · n00b Joined: 03 Dec 2005 Posts: 2

my setup is probably a little different then yours.. i was never able to get the advanced routing to work.
i ended up using two seperate routers for the incoming lines (cisco 2514) and they both go into an old cisco 4500M
both 2514's do natting to the 10 network i use on my lan.

so my mail server has .100 and .101
both IPs are on the same physical interface

so say ISP1 comes in gets natted to .100
ISP2 has a request.. it gets natted to .101

my 4500 has 3 interfaces, one for each router and one for the lan

the lan interface has a routemap asigned..
it basically says anything with source .100 ... set next hop ISP1 gateway
anything .101 set next hop ISP2 gateway...

it has worked like a treat
both my lines are DSL.. so no BGP.

petterg · Guru Joined: 25 Mar 2004 Posts: 500 Location: Oslo, Norway