Using Linux as a router and load balancer between two DSL WAN connections

MikeyCarter · 02-18-2009, 12:37 PM

I have a netgear dual wan router and yesterday the thing locked up and went back to factory defaults. I had a backup of the settings but rather scary when I realized it's a single point of failure that I have no control over, other to buy a new one.

In the process of looking for a new router I had an epiphany. I have a spare laptop, currently with Fedora 10 on it. I started to think, if I added two USB network cards why couldn't it do the same job as the netgear. It would also have the bonus of a built in UPS.

So here's what I want the setup to do.

I want to have two USB network cards connected to two DSL Modems. I want linux to load balance the traffic between the two connections so that an even load is on each interface. The second thing I need is a way to override that based on protocol, IP and/or session. That way VPN connections don't start bouncing between the interfaces. Not to mention the routers "virtual server" scenario for inbound connections.

Does anyone know a good HOWTO doc on accomplishing this task?

acid_kewpie · 02-18-2009, 02:55 PM

in line with most of the results at the bottom of this page, lartc.org chapter 4.

SiliconViper · 04-02-2009, 12:52 AM

While it doesn't cover the full list of things you're asking, this guide on setting up a dual wan system on Linux might provide a reasonable starting point.

MikeyCarter · 04-02-2009, 08:26 AM

All of this was very helpful. I now have my server running with two PPPOE accounts and load balancing between them. (For torrents the highest speed I've seen is 958 kBytes/s.)

I even got creative and did the same for my eth0 and wan0 since NetworkManager activates both devices. Here's the main part:

Code:

########################################################
# Do a check for multiple routes on single Network
########################################################
DefaultRouteIP=$(/sbin/ip route | grep "default via" | awk {'print $3'});
DefaultRoute=$(/sbin/ip route | grep "default via" | awk {'print $5'});
DefaultMask=$(/sbin/ip route | grep "scope link" | grep "$DefaultRoute" | awk {'print $1'})
let TotalRoutes=$(/sbin/ip route | grep "scope link" | grep "$DefaultMask" | wc -l)

if [ $TotalRoutes -gt 1 -a "$DefaultRouteIP" != "" ] ; then
  echo "Found Routes: $TotalRoutes"  >> /var/log/cf_register.log
  BuildCMD="/sbin/ip route change default equalize scope global"
  for routeDev in $(/sbin/ip route | grep "scope link" | grep "$DefaultMask" | awk {'print $3'} | sort -u) ; do
    if [ "$(echo $routeDev | tr -d '[:digit:]')" == "wlan" ] ; then
      BuildCMD=$BuildCMD" nexthop via $DefaultRouteIP dev $routeDev weight 1";
    else
      BuildCMD=$BuildCMD" nexthop via $DefaultRouteIP dev $routeDev weight 2";
    fi
  done
  $BuildCMD;
  /sbin/ip route flush cache
fi

#############################################################
# Do a check for multiple ppp routes
# As in we have multiple dial in or pppoe accounts active
#############################################################
let TotalRoutes=$(/sbin/ip route | grep "scope link" | grep "ppp" | wc -l)

if [ $TotalRoutes -gt 1 ] ; then
  echo "Found Routes: $TotalRoutes"  >> /var/log/cf_register.log
  BuildCMD="/sbin/ip route change default equalize scope global"
  for routeDev in $(/sbin/ip route | grep "scope link" | grep "ppp" | awk -F"dev" {'print $2'} | awk {'print $1'} | sort -u) ; do
      BuildCMD=$BuildCMD" nexthop dev $routeDev weight 1";
  done
  $BuildCMD;
  /sbin/ip route flush cache
fi

I just inserted this code into the /etc/NetworkManager/dispatcher.d/ folder and it runs every time NetworkManager changes.

code in dispatcher.d:

Code:

#!/bin/bash

export LC_ALL=C

echo "Triggered: $(date) $*" 1>> /var/log/cf_register_nm.log 2>&1

if [ "$2" == "down" ]; then
     /usr/bin/cf_register.sh display 1>> /var/log/cf_register_nm.log 2>&1
fi

if [ "$2" == "up" ]; then
     /usr/bin/cf_register.sh display 1>> /var/log/cf_sendmail_nm.log 2>&1
fi