multiple default routes

[ncnaveen_arasu]

                   Dear team,

If we have two routers A & B with two links between them each 10 Mbps and 100Mbps. I will make 100Mbps as primary with default AD and 10Mbps as secondary with AD of 10. i will be defining a two default routes in each router. When primary fails, secondary will work or not. In our case it is not working and we need to remove the primary default route with default AD.

SO kindly clarify how to configure two default routes to the same destination.

If 2 default routes to same destination with same AD wether will it load balance the traffic.

[Abzal]

Hi,

For redundancy you can implement VRRP (Virtual Router Redundancy Protocol).

http://www.cisco.com/en/US/docs/ios/12_0st/12_0st18/feature/guide/st_vrrpx.html

And interface or ip route tracking.

If interface f0/1 will be link to ISP you can track it.  If this link goes down secondary router becomes primary. Because it's priority desreases to 95 (default is 100)

http://www.cisco.com/en/US/docs/ios/12_3t/12_3t2/feature/guide/gtvrrptk.html

track 1 interface f0/1 line-protocol

Or you can track ISP router reachibility:

ip sla 1

 icmp-echo 10.51.12.4

 frequency 3

ip sla schedule 1 start-time now life forever

track 3 rtr 1 reachability

http://www.cisco.com/en/US/docs/ios/ipapp/configuration/guide/ipapp_eot.html#wp1055124

R1(primary):

int f0/0

ip add 10.0.0.254 255.255.255.0

vrrp 1 ip add 10.0.0.1

vrrp 1 priority 150

vrrp 1 preempt

vrrp 1 track 1 decrement 55

vrrp 1 track 3 decrement 55

R2(secondary):

int f0/0

ip add 10.0.0.253 255.255.255.0

vrrp 1 ip add 10.0.0.1

vrrp 1 preempt

Please rate helpful posts.

[Rick Morris]

Sounds like you have the right config.

Can you post the config of the route?

Link A = Gig1 100Mb

Link B = Gig2 10Mb

ip route 0.0.0.0 0.0.0.0 Gig1

ip route 0.0.0.0 0.0.0.0 Gig2 100

I would use the exit interface this way if there is any issue with the interface going down this will force the traffic because it will pull the route from the routing table.  You can use next hop IP as well but as long as the IP appears to be accessible then it is possible the route could not be removed from the routing table.  It should but that is the key word, should.

[ncnaveen_arasu]

Hi Rick,

Thanks for the reply, but in case of Gigabit interface even the WAN link is down, Gigabit interface status and protocol will be up always, so the route with lower AD will not flush out to insert the secondary route. in that case we need to manually shut the primary gigabit link right.

[varununiyal]

Create an IP SLA and bind it with an EEM script....which will manually shut the Gig interface.

ip sla 100

icmp-echo x.x.x.x (next-hop)

ip sla schedule 100 life forever start-time now

track 1 ip sla 100 reachability

event manager applet track-100-down

event track 1 state down

action 1.0 command "config tt"

action 2.0 command "interface gig1"

action 3.0 command "shut"

event manager applet track-100-up

event track 1 state up

action 1.0 command "config tt"

action 2.0 command "interface gig1"

action 3.0 command "no shut"

this is just the rough config but i hope you get the idea.

[Raj Pathak]

Or you can also put your primery deafult route with a track so as soon as the track go down your primery route fush out of you routing tabel.

ip sla 7

icmp-echo " DESTINATION IP "source-ip " SOURCE IP "

frequency 30

ip sla schedule 7 life forever start-time now

track 20 rtr 7 reachability

ip route 0.0.0.0 0.0.0.0 gig1 track 20

ip route 0.0.0.0 0.0.0.0 Gig2 100

2 default routes to same destination with same AD will load balance