Routing Tricks

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Weighted Routing

(aka Load Balancing, Net Balancing)

What is Weighted Routing Simply put, distributing network traffic over multiple paths based on load.

EXAMPLE 1: You have two DSL connections incoming and you distribute your connection traffic between them.

EXAMPLE 2: You have a 1.5Mbs DSL connection and a 3MBs cable connection, therefore you set up your routing to send 1/3 of the traffic out the DSL connection and 2/3 out the cable connection.


How do I do it?

Niels Horn has written a slick little script to do the weighted routing for you. He has given me permission to copy it here.


#!/bin/bash
#
# bal_local		Load-balance internet connection over two local links 
#
# Version:		1.0.0 - Fri, Sep 26, 2008
#
# Author:		Niels Horn <niels.horn(at symbol)gmail.com>
#
#
# Set devices:
DEV1=${1-eth0}	# default eth0
DEV2=${2-ppp0}	# default ppp0
#
# Get IP addresses of our devices:
ip1=`ifconfig $DEV1 | grep inet | awk '{ print $2 }' | awk -F: '{ print $2 }'`
ip2=`ifconfig $DEV2 | grep inet | awk '{ print $2 }' | awk -F: '{ print $2 }'`
#
# Get default gateway for our devices:
gw1=`route -n | grep $DEV1 | grep '^0.0.0.0' | awk '{ print $2 }'`
gw2=`route -n | grep $DEV2 | grep '^0.0.0.0' | awk '{ print $2 }'`
#
echo "$DEV1: IP=$ip1 GW=$gw1"
echo "$DEV2: IP=$ip2 GW=$gw2"
#
### Definition of routes ###
#
# Check if tables exists, if not -> create them:
if [ -z "`cat /etc/iproute2/rt_tables | grep '^251'`" ] ; then
	echo "251	rt_dev1" >> /etc/iproute2/rt_tables
fi
if [ -z "`cat /etc/iproute2/rt_tables | grep '^252'`" ] ; then
	echo "252	rt_dev2" >> /etc/iproute2/rt_tables
fi
#
# Define routing tables:
ip route add default via $gw1 table rt_dev1
ip route add default via $gw2 table rt_dev2
#
# Create rules:
ip rule add from $ip1 table rt_dev1
ip rule add from $ip2 table rt_dev2
#
# If we already have a 'nexthop' route, delete it:
if [ ! -z "`ip route show table main | grep 'nexthop'`" ] ; then
	ip route del default scope global
fi
#
# Balance links based on routes:
ip route add default scope global nexthop via $gw1 dev $DEV1 weight 1 nexthop via $gw2 dev $DEV2 weight 1
#
# Flush cache table:
ip route flush cache  
#
# All done...

To use the script, copy it to /usr/local/bin, make it executable with 'chmod +x' and call it with: Code:

bal_local <dev1> <dev2>

filling in <dev1> and <dev2> with your network-devices. If you call the script without any parameters, it tries to balance eth0 and ppp0 (because this works in my case ).

HERE IS HIS ORIGINAL POSTING

(ALSO, I copied a copy of his permission on my DISCUSSION page)