Re[2]: [LARTC] Redundant Internet connections [Updated]

Re[2]: [LARTC] Redundant Internet connections [Updated]

[Robert Kurjata]

Hi Seth,

I cant find anything more than posting my working script for load
balancing over two links (it was for three links and I home I didn't
remove too much). It has been done strictly by the rules on
Nano-HOWTO and works. The main part is the PING section at the end.
This ensures that kernel sees dead gateways and recovers.
But of course it WILL NOT work without some kernel patching (dead
gateway detection, static routes - just use a Jumbo Patch from
http://www.ssi.bg/~ja/ ).

A final word is: the routers didn't even have to respond to pings.
They need to respond to ARPS. This stuff doesn't work properly for PPP
or PPPoE connections as they usually are NoARP.

I also have some shaping done with TC/CBQ on both links.

VERY IMPORTANT: all the testing is USELESS if you have less than 40-50
users doing lots of requests to different sites as a routes are just
cached in kernel. In my system even with 10-20 users balancing is
usually poor improving greatly with number of users - the diference
between links lowers down to 10%.

Hopefully I will get some free time to write a step-by-step howto
because it took me some time to understand the thing.

Home this helped someone, Greetings to the list
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#!/bin/bash
# This script is done by : Robert Kurjata Sep, 2003.
# feel free to use it in any usefull way

# CONFIGURATION
IP=/sbin/ip
PING=/bin/ping

#--------------- LINK PART -----------------
# EXTIFn - interface name
# EXTIPn - outgoing IP
# EXTMn  - netmask length (bits)
# EXTGWn - outgoing gateway
#-------------------------------------------

# LINK 1
EXTIF1=eth2
EXTIP1EXTM1EXTGW1
# LINK 2
EXTIF2=eth1
EXTIP2EXTM2EXTGW2
#ROUTING PART
# removing old rules and routes

echo "removing old rules"
${IP} rule del prio 50 table main
${IP} rule del prio 201 from ${EXTIP1}/${EXTM1} table 201
${IP} rule del prio 202 from ${EXTIP2}/${EXTM2} table 202
${IP} rule del prio 221 table 221
echo "flushing tables"
${IP} route flush table 201
${IP} route flush table 202
${IP} route flush table 221
echo "removing tables"
${IP} route del table 201
${IP} route del table 202
${IP} route del table 221

# setting new rules
echo "Setting new routing rules"

# main table w/o default gateway here
${IP} rule add prio 50 table main
${IP} route del default table main

# identified routes here
${IP} rule add prio 201 from ${EXTIP1}/${EXTM1} table 201
${IP} rule add prio 202 from ${EXTIP2}/${EXTM2} table 202

${IP} route add default via ${EXTGW1} dev ${EXTIF1} src ${EXTIP1} proto static table 201
${IP} route append prohibit default table 201 metric 1 proto static

${IP} route add default via ${EXTGW2} dev ${EXTIF2} src ${EXTIP2} proto static table 202
${IP} route append prohibit default table 202 metric 1 proto static

# mutipath
${IP} rule add prio 221 table 221

${IP} route add default table 221 proto static \
            nexthop via ${EXTGW1} dev ${EXTIF1} weight 2\
            nexthop via ${EXTGW2} dev ${EXTIF2} weight 3

${IP} route flush cache

while : ; do
  ${PING} -c 1 ${EXTGW1}
  ${PING} -c 1 ${EXTGW2}
  sleep 60
done

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-- 
Pozdrowienia,
 Robert Kurjata

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