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Date:      Thu, 3 May 2001 15:26:18 -1000
From:      "Wai Chan" <waichan@hpu.edu>
To:        "Ted Mittelstaedt" <tedm@toybox.placo.com>
Cc:        <freebsd-net@FreeBSD.ORG>, <freebsd-questions@FreeBSD.ORG>
Subject:   RE: outgoing traffic load balancing with multiple ISP
Message-ID:  <LNEJKGADPHKMLOFLNLFLCEENFAAA.waichan@hpu.edu>
In-Reply-To: <988936570.3af1f97a333bf@mail.freebsd-corp-net-guide.com>

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Our old network admin signed a stupid 5 years contract with ISP 1 (the ISP 1
uses ISP 2 for next hop), and we added ISP 2 when the new network admin
arrived (this network admin is smarter becuase he only signed 1 year
contract with ISP 2).  We cannot get rid of ISP 1 because of the stupid
contract.  Anyway, stand BGP/route load balancing doesn't work very well for
us because all the traffic goes out and in through ISP 2.

We don't want to leave ISP 1's pipe empty.  If the outgoing traffic is using
the IP provided by ISP 1, then the returned traffic will be using ISP 1
provided pipe.  It applies to ISP 2 also.  That's why I am trying to force
half of the traffic (http) use ISP 1 provided IP, and the other half use ISP
2 provided IP.

Thanks!

best wishes,
Wai Chan

-----Original Message-----
From: Ted Mittelstaedt [mailto:tedm@toybox.placo.com]
Sent: Thursday, May 03, 2001 02:36 PM
To: Wai Chan
Cc: freebsd-net@FreeBSD.ORG; freebsd-questions@FreeBSD.ORG
Subject: Re: outgoing traffic load balancing with multiple ISP


Quoting Wai Chan <waichan@hpu.edu>:

> I have two ISPs (two different serial links to my router).  I want 50%
> of
> all outgoing traffic go through ISP 1 with ISP 1 provided IP address as
> source address, and the other 50% of all outgoing traffic go through ISP
> 2
> with ISP 2 provided IP address as source address.
>

Is there any reason you can't just build a second router and plug
the serial link from the second ISP into it, then take the inside
interfaces of both routers and plug them into the same hub, and run multiple
address ranges on the hub?  Then put half of your systems on one IP range
and half of them on the other.

I realize that your not going to divide the traffic up 50% this way but
the problem is (and was just thashed over in this list less than a week
ago) that ISP #1 cannot route IP numbers supplied by ISP #2, and ISP #2
cannot route IP numbers supplied by ISP #1, unless you have been given
entire netblocks by both ISP's and are running BGP with both and are
advertising those netblocks.  Even then, load balancing is a tricky problem
because it's almost entirely dependent on the destination IP numbers that
traffic from your servers is going to.  If you were multihomed with your own
AS
in the manner you would find that in most cases, traffic is going to favor
one
interface over the other.  Generally, if your careful in picking your feeds
it's not going to be worse than 60/40 one way or the other, but if you do
something like using a very well connected network for one link and a poorly
connected network for the other, it can be as bad as 90/10.

Have you investigated bonding or multilink with one of your ISP's?  There's
also a way to multiplex T1's together that some ISP's support.

Ted Mittelstaedt                      tedm@toybox.placo.com
Author of:          The FreeBSD Corporate Networker's Guide
Book website:         http://www.freebsd-corp-net-guide.com


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