Static Routes over Ethernet

[Ahmed Elnagar]

Hello all;

I have two routers connected each with two ethernet cables to a layer 2 switch. see the diagram. I want to get each router to know about each other lan using static routes only i dont want to use dynmaic routes meanwhile preserving the redundancy through the 2 cables. I mean when one cable is down the traffic directs only to the up interface

[kcoley]

There is no way to exchange routing information without using a routing protocol. The term static means you will hardcode route information. In order to accomplish what you want you need to select a routing protocol such as RIP, OSPF, EIRP.

[bjw]

Firstly, what is your routing protocol? EIGRP does a nice automatic load balancing across equal-cost paths. If one link goes down, EIGRP will remove that path from the routing table.

In this case if you just added LAN1 address to Router 1 Eigrp Process and LAN2 address to Router 2 Eigrp process, Eigrp will take care of either load balancing, or routing traffic to a single UP/UP interface.

If you prefer static routes, just add a higher cost to one of the static route statements and EIGRP will use the lower cost link primarily, and will automagicaly swith to a secondary link if the primary fails.

Secondly static routes, if desired could be set up like follows:

Router 1

ip route a.a.a.a b.b.b.b interfaceA

ip route a.a.a.a b.b.b.b interfaceB

Where a.a.a.a b.b.b.b equals the address/mask of the LAN network connected to Router 2

Router 1

ip route c.c.c.c d.d.d.d interfaceA

ip route c.c.c.c d.d.d.d interfaceB

Where c.c.c.c d.d.d.d equals the address/mask of the LAN network connected to Router 1

[Ahmed Elnagar]

Hello and thanks for ur fast responses;

for bjw first there is two LANs in this topology because each router has 2 interfaces in differenet subnets (that is a Router characterstic) then if I add the static routes as you mentioned the problem when interface A of router1 goes down and Router2 will not sense this action and still send traffic to that interface. the main point is here.

[Richard Burts]

You have correctly identified one of the issues about using static routes with Ethernet interfaces. Cisco has introduced a new feature which addresses this issue. It is Reliable Static Routes with Object Tracking. It uses static routes and it dynamically tracks the state of some remote object and if you lose connectivity over a particular interface then the static route using that interface is removed from the routing table.

This link has information to help you understand this feature and how to configure it:

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

HTH

Rick

[bjw]

If you use EIGRP, you just enter the desired networks in the EIGRP process. A routing table is built and EIGRP will share it's routes with other routers. If a router interface goes down, routes in the routing table that use that interface will be removed and new routes will be discovered. Routers care about how to get packets from one place to another. If Router 1 says it has LAN1 connected. That LAN is in the routing table, it shares that with Router 2's Routing process.

If you allow all attached networks to be advertised, the Routing process will adjust itself to a new path.

Example:

Router 1 Interface FA0 10.1.1.0/24 LAN1

Interface FA1 100.1.1.1/24 to switch VLAN A

Interface fa2 200.1.1.1/24 to switch VLAN B

Router 2 Interface FA0 10.2.1.0/24 LAN2

Interface FA1 100.1.1.2/24 to switch VLAN A

Interface fa2 200.1.1.2/24 to switch VLAN B

Router 1 EIGRP

EIGRP 1

Network 10.1.1.0

no auto summ

Router 2 EIGRP

EIGRP 1

Network 10.2.1.0

no auto summ

The routing table will show all defined networks and will show 2 routes to each LAN.

When 1 route (interface) goes away, that route is removed and the second route used

[Ahmed Elnagar]

Thank you very much for ur following

I think the Reliable static routing will do it I am trying it write now and I will give u a feedback

for Bjw I am not permitted to use routing protocols atall in the network.

[Ahmed Elnagar]

Unfortunalty It requires software version 12.3(2)XE and I have 12.2(18)SXD3 on a 7600 router. well I will think of a software upgrade but anyway this feature is very interesting and it worth the try I will try it and I will give u a feedback when I will ISA. thanks for ur support