Cisco: Track default route when Outside IP address is assigned VIA DHCP

Sometimes you need to to apply a tracking statement to a route so that if a cretin condition is met that route gets removed. In this case I needed to have the default route fail over to a second internet connection if the primary internet went down. Except, we receive a DHCP IP address on the primary connection so I can not just track reach ability to the next hop as that IP address changes. So here is a way to do tracking statements with a DHCP default route. We just set the default route to the interface instead of a IP address.


track 1 ip sla 10 reachability
 delay down 30 up 30 (This makes it so that when there is a failure on the IP SLA it waits 30 seconds to make the change, this is so that it doesn't flap up/down)

ip sla auto discovery
ip sla 10
 icmp-echo 8.8.4.4 source-interface GigabitEthernet0/1
 tag Ping Google
 threshold 1000
 timeout 2000
 frequency 3
ip sla schedule 10 life forever start-time now

(The above section is where you configure an IP address that you want to monitor, the router will send out a ping packet to that IP address to determine readability up/down)

interface GigabitEthernet0/1
ip dhcp client default-router distance 1
ip dhcp client route track 1

ip route 8.8.8.8 255.255.255.255 GigabitEthernet0/1 (Always forces this traffic out this interface so we dont end up sending over the backup)

ip route 0.0.0.0 0.0.0.0 GigabitEthernet0/1 track 1 (Primary internet connection default route with a tracking statement)

ip route 0.0.0.0 0.0.0.0 GigabitEthernet0/2 200 (Back up internet connection default route)