ddwrt-split-gateway-328595.sh

#!/bin/sh
# installation: copy/paste this script into shell (telnet/ssh) window

WANUP_DIR="/jffs/etc/config"
WANUP_SCRIPT="$WANUP_DIR/alt-gtwy.wanup"

mkdir -p $WANUP_DIR

cat << "EOF" > $WANUP_SCRIPT
#!/bin/sh
set -x # uncomment/comment to enable/disable debug mode
(
TID='200'

ALT_GTWY='192.168.1.88'

# source IPs to be routed via 192.168.1.1
SOURCE_IP='
192.168.3.177
192.168.3.178
192.168.3.179
192.168.3.180
192.168.3.181
192.168.3.182
192.168.3.183
192.168.3.184
192.168.3.185
192.168.3.186
192.168.3.187
'

# required for serialization when reentry is possible
LOCK="/tmp/$(basename $0).lock"
acquire_lock() { while ! mkdir $LOCK >/dev/null 2>&1; do sleep 10; done; }
release_lock() { rmdir $LOCK >/dev/null 2>&1; }

# optional (allows recovery period of two minutes)
#sleep 120

# wait for *reliable* internet connection
while ! ping -qc1 -w3 8.8.8.8 >/dev/null 2>&1; do sleep 3; done; sleep 10

# one instance at a time
acquire_lock

# catch premature exit and cleanup
trap 'release_lock; exit 1' SIGHUP SIGINT SIGTERM

# cleanup from possible prior execution
{
ip route del   0.0.0.0/1 via $ALT_GTWY
ip route del 128.0.0.0/1 via $ALT_GTWY
while ip rule del from 0/0 to 0/0 table $TID 2>/dev/null; do :; done
ip route flush table $TID
ip route flush cache
} 2>/dev/null

# copy main routing table to alternate
ip route | while read route; do ip route add $route table $TID; done

# override main routing table w/ alternate gateway
ip route add   0.0.0.0/1 via $ALT_GTWY
ip route add 128.0.0.0/1 via $ALT_GTWY

# start split gateway
for ip in $SOURCE_IP; do ip rule add from $ip table $TID; done

# force routing system to recognize changes
ip route flush cache

# any concurrent instance(s) may now run
release_lock

exit 0

) 2>&1 | logger -t $(basename $0)[$$] &
EOF
chmod +x $WANUP_SCRIPT
#