# add routing tables
# flush old tables
ip route flush table $TABLE1
ip route flush table $TABLE2
# add new table
ip route add $GW1 dev $DEV1 src $IP1 table $TABLE1
ip route add default via $GW1 table $TABLE1
ip route add $GW2 dev $DEV2 src $IP2 table $TABLE2
ip route add default via $GW2 table $TABLE2

# add rule for lookup
# remove old rule
ip rule del from $IP1 table $TABLE1
ip rule del from $IP2 table $TABLE2
ip rule del fwmark 1 table $TABLE1
ip rule del fwmark 2 table $TABLE2
# add new rule
ip rule add from $IP1 table $TABLE1
ip rule add from $IP2 table $TABLE2
ip rule add fwmark 1 table $TABLE1
ip rule add fwmark 2 table $TABLE2

# iptables rules for SNAT:
iptables -t nat -A POSTROUTING -o ppp0 -j SNAT --to-source $IP1
iptables -t nat -A POSTROUTING -o ppp1 -j SNAT --to-source $IP2

# iptables for marking packet from originate source
iptables -t mangle -A PREROUTING          -m state --state ESTABLISHED,RELATED -j CONNMARK --restore-mark
iptables -t mangle -A OUTPUT              -m state --state ESTABLISHED,RELATED -j CONNMARK --restore-mark
iptables -t mangle -A PREROUTING -i ppp0  -m state --state NEW                 -j CONNMARK --set-mark 1
iptables -t mangle -A PREROUTING -i ppp1  -m state --state NEW                 -j CONNMARK --set-mark 2
iptables -t mangle -A PREROUTING -m connmark --mark 1                          -j MARK --set-mark 1
iptables -t mangle -A PREROUTING -m connmark --mark 2                          -j MARK --set-mark 2
iptables -t mangle -A PREROUTING -m connmark ! --mark 0 -m state --state NEW   -j CONNMARK --save-mark