WikiDevi.Wi-Cat.RU:DD-WRT/Dual WAN with failover

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This was tested on WRT54GL 1.1 with DD-WRT 2.4 mini.

What this setup will do

Create a second WAN port, so you can hook up another provider for backup, and will change the active provider to the secondary, if ping fails to the provider's gateway. It will ping in a predefined interval. If this is not what you need, then you might try:

Creating a second VLAN

You'll need to create a new VLAN, called vlan2. Enter in the web interface, Settings/VLANs. Set Port 4 to a new VLAN. Enter in the console, and do the following commands

Commands to set VLANs

nvram set vlan0ports="1 2 3 5*"
nvram set vlan2ports="0 5"
nvram set vlan2hwname=et0
nvram commit

On a WRT54GL this will be port 4, if you want port 1 for vlan2 then set vlan2ports to "3 5".

Setting up the scripts

We'll have some scripts, which will go in /jffs/etc/config.

Bringing up the second WAN at startup

wan2up.startup

Now this is for static IP, but you can change this situation by modifying the script for udhcpc 

#!/bin/sh
WAN2_IFNAME=vlan2
WAN2_IPADDR=192.168.2.2
WAN2_GATEWAY=192.168.2.1
WAN2_NETMASK=255.255.255.0
if [ "$(nvram get wan2_ipaddr)" != "$WAN2_IPADDR" ]; then
        nvram set wan2_ifname=$WAN2_IFNAME   
   nvram set wan2_ipaddr=$WAN2_IPADDR
   nvram set wan2_gateway=$WAN2_GATEWAY
   nvram set wan2_netmask=$WAN2_NETMASK
   nvram commit
fi
ifconfig $(nvram get wan2_ifname) up $(nvram get wan2_ipaddr) netmask $(nvram get wan2_netmask)
# We will want to set masquerade on WAN2, otherwise after changing active WAN, we'll remain up in the air.
iptables -t nat -A POSTROUTING -o vlan2 -j MASQUERADE

Setting up the scripts responsible for switching to a specific WAN

This file makes the changes necessary to activate WAN1. Change the nameservers to your provider's DNS servers or OpenDNS's.

wan1.up

#!/bin/sh
# WAN1 
DEV=vlan1
GATEWAY=`nvram get wan_gateway` 
DNS1=193.226.43.33
DNS2=193.230.175.1

nvram set wan_dns="$DNS1 $DNS2"
ip route delete default
# ip route delete default
ip route add default via $GATEWAY dev $DEV
echo "nameserver $DNS1" >/tmp/resolv.dnsmasq
echo "nameserver $DNS2" >>/tmp/resolv.dnsmasq
pr="$(ps|awk '/dnsmasq/ {print $1}')"
kill -9 $pr
dnsmasq --conf-file=/tmp/dnsmasq.conf

As you probably already figured out, this will make the changes necessary to activate WAN2 :)

wan2.up

#!/bin/sh
# WAN2 
DEV=vlan2
GATEWAY=`nvram get wan2_gateway` 
DNS1=193.226.43.33
DNS2=193.230.175.1

nvram set wan_dns="$DNS1 $DNS2"
ip route delete default
# ip route delete default
ip route add default via $GATEWAY dev $DEV
echo "nameserver $DNS1" >/tmp/resolv.dnsmasq
echo "nameserver $DNS2" >>/tmp/resolv.dnsmasq
pr="$(ps|awk '/dnsmasq/ {print $1}')"
kill -9 $pr
dnsmasq --conf-file=/tmp/dnsmasq.conf

Setting up the actual failover script

Now, this is the core of our goal, this script will monitor the active connection, and if connection fails, it will call one of wan1.up or wan2.up to change the active connection.

failover.startup

#!/bin/sh
INTERVAL=10
PACKETS=1
USINGWAN=0
WAN1=vlan1
WAN2=vlan2
WAN1GW=`nvram get wan_gateway`
WAN2GW=`nvram get wan2_gateway`

# We'll run this in the intervals given above
while sleep $INTERVAL
do
        # Try to figure out the current route
        TARGET=`ip route | awk '/default via/ {print $3}'`
        # Set the variable, so let the script now which connection is it dealing with
        if [ "$WAN1GW" = "$TARGET" ]; then 
                USINGWAN=1;
        else if [ "$WAN2GW" = "$TARGET" ]; then
                USINGWAN=2;
          fi;
        fi
        # We'll ping as many times the $PACKETS variable tells, and test if we have connection:
        RET=`ping -c $PACKETS $TARGET 2>/dev/null | awk '/packets received/ {print $4}'`
        # If we don't have connection, change the active WAN port (If there is any loss with multiple packets, it should change either)
        if [ "$RET" -ne "$PACKETS" ]; then
                if [ "$USINGWAN" = "1" ]; then
                        /jffs/etc/config/wan2.up
                        USINGWAN=2
                        echo "Changed active WAN port to 2!"
                else
                        /jffs/etc/config/wan1.up
                        USINGWAN=1
                        echo "Changed active WAN port to 2!"
                fi
        fi 
done;

Optionally add automatic switching back to WAN1 once it becomes available

When WAN2 is in use as the active WAN port the script will check the status of WAN1 at the regular interval and switch back to it when it becomes available. Useful if WAN2 is a slower or paid-use connection.

Add these lines to failover.startup just before the last line (done;). 

if [ "$USINGWAN" = "2" ]; then
WAN1STAT=`ping -c $PACKETS $WAN1GW 2>/dev/null | awk '/packets received/ {print $4}'`
if [ "$WAN1STAT" = "$PACKETS" ]; then
/jffs/etc/wan1.up
USINGWAN=1
echo "Changed active WAN port to 1!"
fi
fi

Setting up the script responsible for the Easy Setup button

Optionally, if you want to be able to switch the active WAN port with the Easy Setup button, you can add:

chwan.sesbutton

#!/bin/sh
USINGWAN=0
WAN1=vlan1
WAN2=vlan2
WAN1GW=`nvram get wan_gateway`
WAN2GW=`nvram get wan2_gateway`

        TARGET=`ip route | awk '/default via/ {print $3}'`
        if [ "$WAN1GW" = "$TARGET" ]; then 
                USINGWAN=1;
        else if [ "$WAN2GW" = "$TARGET" ]; then
                USINGWAN=2;
          fi;
        fi
ip route delete default
if [ "$USINGWAN" = "1" ]; then
        /jffs/etc/config/wan2.up
        USINGWAN=2
        echo "Changed active WAN port to 2!"
        else
        /jffs/etc/config/wan1.up
        USINGWAN=1
        echo "Changed active WAN port to 1!"
fi

Final polishing

Create above files in /jffs/etc/config and then do a 

chmod +x /jffs/etc/config/*

If you made everything as written above right, you should reboot the router and enjoy!

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