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Re: NAT Configuration for Dual WAN Router

  • From: My Name
  • Date: Sun Dec 18 09:19:49 2005
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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@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@sendjoeanemail.com






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