NAT Configuration for Dual WAN Router

Sun Dec 18 14:17:55 UTC 2005

Assuming your providers give you a new modem which is already NAT'ing the
LAN side of the modem and you are plugging that into multiple NIC's on your
linux router like;

-modem-pub -> modem-priv -> linux-eth0
-modem-pub -> modem-priv -> linux-eth1
-linux-eth3 -> LAN switch

1) Configure VRRP (http://sourceforge.net/projects/vrrpd/) on eth0 and eth1
WAN side on the linux router.  You should be able to configure the weighting
on each interface equally so that they 'load share' (I've done this in
FreeBSD).

2) Set the default gateway on the linux router to the VRRP interface (IP
that is shared between eth0 and eth1).

This would be a very scalable and reliable solution for this type of
network.  I've never tried it, but let me know if it works!

On 12/14/05, Joe Johnson <nanog at sendjoeanemail.com> wrote:
>
>
> I've been trying over and over to figure this one out, but I'm just
> hitting
> the end of my wits.  We have a remote office that can only get 768Kbps
> DSL,
> which they've not totally maxed out.  So management's solution now is to
> buy
> a second DSL line, but they won't let me buy a dual WAN router (in case
> they
> add a 3rd DSL line).
>
> I've found some great articles on how to get the interfaces working with 2
> default gateways (I used this:
>
> http://www.linuxquestions.org/linux/answers/Networking/Spanning_Multiple_DSL
> s) and that is all running fine.  It alternates every few minutes which
> WAN
> port is used when I traceroute yahoo.com (which is fine) and everything is
> connecting fine from the router.  However, I can't figure out how to get
> NAT
> running on the server for the 2 WAN ports for clients inside the LAN.  I
> can
> NAT to 1 DSL, but that is useless.
>
> What I am looking for is a tutorial in how to do this or a pointer to
> someone who can help.  Anyone know of a resource for this?
>
>
>
> Joe Johnson
> joe at sendjoeanemail.com
>
>
>
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