source: lab.git/TipAndDoc/iproute/setroute.sh

#!/bin/sh

# set individualized routing table and policy for each network device


set -x

## INTERFACES(5)
# IFACE  physical name of the interface being processed
# METHOD method of the interface (e.g., static)
# MODE   start if run from ifup, stop if run from ifdown
# PHASE  as per MODE, but with finer granularity, distinguishing the pre-
#        up, post-up, pre-down and post-down phases.

# optional arugument to set default gateway manually
GATEWAY=$1

TID=`/sbin/ip addr show dev ${IFACE} | grep -w ${IFACE}: | tr -s ' ' | cut -d : -f 1`

if [ "${PHASE}" = "post-down" ]; then
    # delete routing table and policy and exit
    ## routing table is automatically flushed, so 'route flush' can be removed
    /sbin/ip route flush table ${TID}
    ## device has no longer any IP addr, so do not use IPADDR
    /sbin/ip rule del table ${TID} priority ${TID}
    /sbin/ip route flush cache
    echo "remove routing table and policy for ${IFACE}"
    exit
fi


# get IP address, network mask, default gateway info
IPADDR=`/sbin/ip addr show dev ${IFACE} | grep -w inet | tr -s ' ' | cut -d ' ' -f 3 | cut -d / -f 1`
if [ -z "${IPADDR}" ]; then
    # fail to bind IP address to device
    echo "${IFACE} has no IP address."
    exit
fi
NETWORK=`/sbin/ip route show dev ${IFACE} | grep -w ${IPADDR} | tr -s ' ' | cut -d ' ' -f 1`

if [ -z "${GATEWAY}" ]; then
    GATEWAY=`/sbin/ip route show dev ${IFACE} | grep -w default | tr -s ' ' | cut -d ' ' -f 3`
fi
if [ -z "${GATEWAY}" ]; then
    GATEWAY=`/sbin/ip route | grep -w default | tr -s ' ' | cut -d ' ' -f 3`
    # this may add wrong default route especially on RHEL
fi


# set routing table
/sbin/ip route add ${NETWORK} dev ${IFACE} table ${TID}
/sbin/ip route add default via ${GATEWAY} dev ${IFACE} table ${TID}

# set routing policy
/sbin/ip rule add from ${IPADDR} table ${TID} priority ${TID}

/sbin/ip route flush cache
echo "add routing table and policy for ${IFACE} on table ${TID}"