OER (Optimized Edge Routing) Basic Configuration

In this lesson I want to show you a basic configuration of OER (Optimized Edge Routing). If you have no idea what OER is or why you want to use this, take a look at my introduction to OER first.

OER is not a simple topic and the configuration can become quite complex because of all the policies. In this example i’m going to walk you through a simple scenario where we configure an MC (Master Controller) and BR (Border Router). Let me show you the topology:

optimized edge routing demo topology

There are quite some routers so let me explain this topology to you:

  • R1,R2 and R3 belong together, the serial links on R3 are the “edge” of our network.
  • R3 will be configured as the master controller but also as a border router. You can configure both on the same router.
  • R3 has two serial links that we will use as “WAN” links. The serial 1/1 interface has a bandwidth of 64 kbps and the serial 1/0 interface has a bandwidth of 1024 kbps.
  • R1 and R2 will be used as “traffic generators”.
  • R1 will have a TCP connection to the loopback0 interface of R6.
  • R2 will send ICMP traffic to the loopback1 interface of R6.
  • R4 and R5 are nothing special, they are only used as endpoint for the serial links.
  • R6 is only used as an endpoint for our “traffic generators” R1 and R2.

By default I will send all traffic over the slow 64 kbps link using a static route, we will use a floating static route to use the 1024 kbps link as a backup. The goal of this lab example is to configure OER to automatically switch traffic flows from the slow 64 kbps link to the 1024 kbps link. Sounds like fun right?

Let’s get to the configuration part!

To keep things simple I will use static routes for connectivity:

R1(config)#ip route
R2(config)#ip route

R1 and R2 will use a static route pointing to R3.

R3(config)#ip route
R3(config)#ip route 5

R3 has two default routes. The first one points to R5 and this is the static route that we will find in the routing table. The second static route is our floating static route pointing to R4. It has an administrative distance of 5.

Something that you should remember about OER is that it requires a “parent route” in order to use a certain link. If I didn’t configure the static route pointing to R4 than OER will never be able to use the serial 1/0 interface!
R4(config)#ip route
R4(config)#ip route
R4(config)#ip route
R5(config)#ip route
R5(config)#ip route
R5(config)#ip route

On R4 and R5 we will configure static routes so they can reach the /24 network and the loopback interfaces of R6.

R6(config)#ip route
R6(config)#ip route

On R6 we’ll configure two default routes pointing towards R4 and R5. I don’t care which path R6 will use…

Let’s check if R1 and R2 can reach R6:


Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to, timeout is 2 seconds:
Success rate is 100 percent (5/5), round-trip min/avg/max = 8/11/12 ms


Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to, timeout is 2 seconds:
Success rate is 100 percent (5/5), round-trip min/avg/max = 8/16/32 ms

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to, timeout is 2 seconds:
Success rate is 100 percent (5/5), round-trip min/avg/max = 8/11/12 ms


Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to, timeout is 2 seconds:
Success rate is 100 percent (5/5), round-trip min/avg/max = 8/16/32 ms

R1 and R2 can reach R6 so my static routes are working. Let’s check the path that they are currently using:


Type escape sequence to abort.
Tracing the route to

1 4 msec 4 msec 4 msec
2 8 msec 8 msec 8 msec
3 8 msec *  8 msec

We are using the path from R3 to R5, this is because of the default route that I configured on R3:

R3#show ip route static
S* [1/0] via

So far so good, connectivity is working. Before I start with the configuration of OER I want to change the bandwidth of the serial interfaces on R3:

R3(config)#interface serial 1/1
R3(config-if)#bandwidth 64
R3(config)#interface serial 1/0
R3(config-if)#bandwidth 1024
R3#show interfaces serial 1/1 | include BW
MTU 1500 bytes, BW 64 Kbit, DLY 20000 usec,
R3#show interfaces serial 1/0 | include BW
MTU 1500 bytes, BW 1024 Kbit, DLY 20000 usec,

R3 now thinks that serial 1/1 is 64kbit and serial 1/0 is 1024 kbit. Of course this doesn’t change the actual bandwidth but OER will believe that this is the bandwidth of the interfaces. Now let’s take a look at OER!

oer internal external interfaces

When we configure OER we have to configure the master controller and the border router(s). OER needs to know what the internal and external interfaces are. R3 will be both a border router and the master controller. The FastEthernet 0/0 interface is internal and the two serial links are external. OER requires authentication and it has to be done with a key chain just like EIGRP. Here’s what the configuration looks like:

R3(config)#key chain OER
R3(config-keychain)#key 1
R3(config-keychain-key)#key-string NETWORKLESSONS

I’ll keep it simple, the key chain is called “OER” and the password will be “NETWORKLESSONS”. Now let’s configure the master controller role:

We're Sorry, Full Content Access is for Members Only...

If you like to keep on reading, Become a Member Now! Here is why:

  • Learn any CCNA, CCNP and CCIE R&S Topic. Explained As Simple As Possible.
  • Try for Just $1. The Best Dollar You've Ever Spent on Your Cisco Career!
  • Full Access to our 660 Lessons. More Lessons Added Every Week!
  • Content created by Rene Molenaar (CCIE #41726)

510 Sign Ups in the last 30 days

100% Satisfaction Guaranteed!
You may cancel your monthly membership at any time.
No Questions Asked!

Tags: , , ,

Forum Replies

  1. Hi Rene,

    I am just wondering if you have seen this technology deployed in any production networks

    It sounds like a predecessor of SDN and with a great potential, but I am not sure if it has been widely deployed


  2. Hi Purushotham,

    I probably might add some extra Pfr material since it’s on the CCIE written exam, it’s not in the lab anymore though. About IWAN…I’d have to check what is included. I do have quite some DMVPN material.


  3. Hi Rene,

    I feel many concepts easy when I hear it from you. I will wait for your material on Pfr.

    Thank you for the response.

  4. Hi Rene and staff,
    thanks for your work through the forum
    Please, could you give some more explanation about the apparent contradiction below:

    1. using routes that have the same cost, OSPF can do load balancing (ECLB) on a per packet basis, that is each packet of a same flow may take a different link
    2. the router has to use CEF and CEF can’t do load balancing but only load sharing

  5. Hello Dominique

    The two statements are referring to two separate situations. The first is referring to the use of OSPF without CEF. That is, OSPF using only process switching. This uses the CPU for all routing decisions. Under these circumstances, ECLB is achieved for OSPF.

    The second situation involves a router that has CEF enabled. What is being said here is essentially that the mechanism for sending packets over multiple paths to their destinations is different. Various terms are used interchangeably, such as load balancing and load sharing, even withi

    ... Continue reading in our forum

6 more replies! Ask a question or join the discussion by visiting our Community Forum