[CentOS] iproute create policy routes after reboot

Robin Mordasiewicz robin at bullseye.tv
Sun Oct 30 03:55:23 UTC 2005

On Fri, 28 Oct 2005, Robin Mordasiewicz wrote:

> Which files do I need to edit in order to initialize a route after a reboot.
> I have a 802.1q tagged VLAN interface which I need to create a rule, and a 
> route for.
> I see on my CentOs 4.2 box that in /etc/iproute2 there are the following 
> files. I realize that I can add my tables to /etc/iproute2/rt_tables, but 
> when I want to create a rule I am not sure where to put the information for 
> the next reboot.

I wrote the following /sbin/ifup-local script. Mebbe someone has something 
to say...

<snip /sbin/ifup-local>
# Robin Mordasiewicz <robin at bullseye.tv>
# The following script is copied and pasted together from the existing
# network startup scripts found on RedHat-AS/CentOS

# This custom script is run last. This is called by the ifup-post script
# on a RedHat/CentOS based system.
# This script will add a routing table and a rule for each VLAN interface
# so that when responding to traffic from a box with multiple tagged VLAN
# interfaces the proper VLAN tags are added.

# The problem is that Linux repsonds to traffic based on the routing
# table, which means that packets which are sent out the device which the
# default gateway is configured will be tagged with the wrong VLAN

# The only devices that this script should act on are tagged VLAN
# interfaces Tagged VLAN interfaces will be in the form bond0.xxx, or
# eth0.xxx. Other regular devices such as lo, eth0, or bond0 should not
# require this script to run

# This requires that you have a "GATEWAY=x.x.x.x", "TABLE=???", and
# optionally a "PRIORITY=xx" configured in the interface config,
# ie. /etc/sysconfig/network-scripts/ifcfg-bondx.xxx,
# or /etc/sysconfig/network-scripts/ifcfg-ethx.xxx

# It is also required that your tables are properly listed in
# /etc/iproute2/rt_tables

# For more information read the following websites.
# http://www.linuxjournal.com/article/7291
# http://lartc.org/howto/lartc.rpdb.html
if echo ${1} | LANG=C egrep -v '(:)' | LANG=C egrep -q \
           '(eth|bond)[0-9][0-9]*\.[0-9][0-9]?[0-9]?[0-9]?'; then
     . /etc/init.d/functions

     cd /etc/sysconfig/network-scripts
     . network-functions

     [ -f ../network ] && . ../network


     [ -z "${CONFIG}" ] && {
         echo $"Usage: ifup <device name>" >&2
         exit 1

     need_config ${CONFIG}

     [ -f "${CONFIG}" ] || {
         echo $"$0: configuration for ${1} not found." >&2
         echo $"Usage: ifup-local <device name>" >&2
         exit 1


     if [ -z "$TABLE" -o -z "$GATEWAY" ]; then
         exit 0

     VID="`echo ${DEVICE} | \
         LANG=C egrep '(eth|bond)[0-9]+\.[0-9][0-9]?[0-9]?[0-9]?$' | \
         LANG=C sed 's/^[a-z0-9]*\.//g;s/^0*//'`"
     PHYSDEV="`echo ${DEVICE} | \
         LANG=C egrep '(eth|bond)[0-9]+\.[0-9][0-9]?[0-9]?[0-9]?$' | \
         LANG=C sed 's/\.[a-z0-9]*$//g'`"

     if [ -z ${PRIORITY} ]; then
     action $"Setting default route ${GATEWAY} for table: ${TABLE}" \
        /sbin/ip route replace default via ${GATEWAY} dev ${DEVICE} \
            table ${TABLE}

     while `ip rule list | LANG=C egrep -q \
       "from ${IPADDR} lookup ${TABLE}"`; do
           /sbin/ip rule delete from ${IPADDR} lookup ${TABLE}

     action $"Setting Source ${IPADDR} to use routing table: ${TABLE}" \
         /sbin/ip rule add from ${IPADDR} table ${TABLE} \
             priority ${PRIORITY}


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