Cisco Support Community
cancel
Showing results for 
Search instead for 
Did you mean: 
New Member

2 static routes / 2 nexthops on same LAN

Hi everyone!

I have this question, even could be a little dummie.

I have a LAN environment, for example on this interface on R1:

hostname R1

!

int fa0/0

ip address 192.168.1.1 255.255.255.0

!

And there is another router R2 connected to the same LAN segment, with the ip address:

Hostname R2

!

int Fa0/1

192.168.1.2 255.255.255.0

!

Im reaching a remote network from R1with static routing :

Hostname R1

ip route 10.10.10.0 255.255.255.0 192.168.1.2

This is from R1 im reaching the net 10.10.10.0/24 through R2 (192.168.1.2)

We also have a third router R3, with IP:

Hostname R3

!

int fa0/1

ip address 192.168.1.3

!

All 3 routers on the same segment..

We want to do a static floating route from R1 in order that, when R2 goes down, the traffic could be send on R3, for example:

Hostname R1

ip route 10.10.10.0 255.255.255.0 192.168.1.3 200 <--dist. 200

The thing is that as the 3 routers are on the same segment, if R2 goes down, the subnet 192.168.1.0/24 still will be alive on the RIB..

As far as i know, the FIB would clear the adjacency for 192.168.1.2 (R2), but the RIB will keep alive the first route throught R2 because the segment is still alive..

Do you know how could be avoid this?

We can?t use dynamic routing protocols, nor HSRP, and we cant configure any other L3 interface..

As i think, there would be noissue with FIB, because the ARP timeout would glean the adjacency, but the RIB would keep the 1st route available...

Any ideas?

Thanks!

Regards

2 REPLIES
New Member

Re: 2 static routes / 2 nexthops on same LAN

ok u can t use dynamic protocols nor HSRP, you can use a bad solution: just use 2 static routes with default dist:

R1:

ip route 10.10.10.0 255.255.255.0 192.168.1.2

ip route 10.10.10.0 255.255.255.0 192.168.1.3

then the router will send a copy of the paquet to each router. but i don t know how your application will do when it receives duplicate copy of the paquet.as i said it s a bad solution. but i can t see an other way ;-)

Hall of Fame Super Silver

Re: 2 static routes / 2 nexthops on same LAN

Oussama

In your solution the router will have two entries for the destination in the routing table. But it will not send a copy of the packet to each router but will send some packets to one next hop and will send other packets to the other next hop. This is not the desired outcome.

Cisco has recognized the problem with static routes with a next hop over a LAN interface will not be withdrawn while the LAN interface is still active. Cisco has provided a solution to this with a feature called Reliable Static Routes with Object Tracking. This link should give you the information to configure it and to solve the problem:

http://www.cisco.com/en/US/products/sw/iosswrel/ps5413/products_feature_guide09186a00801d862d.html

HTH

Rick

106
Views
0
Helpful
2
Replies
CreatePlease to create content