PBR/Route-Map Clarification

[merryllem]

Greetings all,

I have the following configs

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route-map ChangeDefaultRoute permit 10
description << Route map to set default route for yards >>
set ip default next-hop 1.1.1.1 1.1.1.2

interface f0/0
ip policy route-map ChangeDefaultRoute

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Basically match any traffic coming from f0/0 and change the default route to the two gateways I have assigned. The clarification I need is, what does having two IP's in the "set ip default next-hop" line mean. Would it mean that traffic will be load balanced out to the gateways? Would the router perform any "fail check" to see if the next hop's are alive and forward accordingly? Or do I need to add the verify-availability function on the line to perform fail checks.

Thanks in Advance.

[cadet alain]

Hi,

Don't forget ip default next-hop is not the same behaviour as ip next-hop : in former then the routing table default-gateway is tried first.

Putting more than one next-hop as far as I know means he is gonna try them in the order you configured and take the first one for which outgoing interface is up/up.

Regards.

Alain.

[merryllem]

Thanks for the reply, "default next-hop" is the behavior that I do intend, changing the default route of traffic coming from the F0/0 interface. One thing I forgot to mention is the "next-hops" in the configuration goes out of the same interface so fail check must not rely on the physical connection but on the remote end reachability instead.

[Andy Roberts]

Hi,

Have you tried using IP SLA and tracking to verify next hop availablity ?

I use the folowing and it works superb;

ip sla 1
icmp-echo 10.172.1.1
ip sla schedule 1 life forever start-time now
ip sla 2
icmp-echo 10.172.1.254
ip sla schedule 2 life forever start-time now

track 101 rtr 1 reachability

track 102 rtr 2 reachability

route-map DEFAULT-POLICY permit 10
description Sets next-hop of local traffic  match ip address LOCAL-NETS
set ip next-hop verify-availability 10.172.1.1 20 track 101
set ip next-hop verify-availability 10.172.1.254 10 track 102

[Saurabh Nautiyal]

Hello,

With 2 next hop IP  address in set statement router will use the IP address in order and if first hop is not reachable ( no route because of interface down) then will try to use the second next hop. Since your next hop is reachable via same interface and  if that interface goes down router will not be able to use both next hop IP address.

You have to make sure that tracking options are available with "default" keyword. I am not sure if PBR with object tracking is supported when you use "default" keyword in the set statement. It is definetely available without it.

Thanks,

Saurabh