# Introduction to OER (Optimized Edge Routing)
**URL:** https://forum.networklessons.com/t/introduction-to-oer-optimized-edge-routing/962
**Category:** Lessons Discussion
**Created:** [December 24, 2016, 6:46pm UTC](https://forum.networklessons.com/t/introduction-to-oer-optimized-edge-routing/962 "2016-12-24T18:46:08Z")
**Posts on this page:** 12
**Page:** 1
### Author:  [@ReneMolenaar](https://forum.networklessons.com/u/ReneMolenaar)
#### Post date: [December 24, 2016, 6:46pm UTC](https://forum.networklessons.com/t/introduction-to-oer-optimized-edge-routing/962/1 "2016-12-24T18:46:08Z")
This topic is to discuss the following lesson:
> **[Introduction to OER (Optimized Edge Routing)](https://networklessons.com/ip-routing/why-use-oer-optimized-edge-routing-or-pfr-performance-routing)**
>
> OER (Optimized Edge Routing) adds intelligence to the network by choosing the best exit path for our traffic. This introduction explains why you want OER.
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### Author:  [@csoler](https://forum.networklessons.com/u/csoler)
#### Post date: [January 24, 2016, 10:08pm UTC](https://forum.networklessons.com/t/introduction-to-oer-optimized-edge-routing/962/3 "2016-01-24T22:08:20Z")
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
Thanks,
C
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### Author:  [@ReneMolenaar](https://forum.networklessons.com/u/ReneMolenaar)
#### Post date: [January 25, 2016, 8:07pm UTC](https://forum.networklessons.com/t/introduction-to-oer-optimized-edge-routing/962/4 "2016-01-25T20:07:15Z")
Hi C,
I haven’t seen this in production networks before. The idea behind it is pretty cool, one “controller” that determines what paths to use for the network. OER however on IOS 12.4 was pretty buggy, it’s better on IOS 15 as PFR (Performance Routing).
SDN goes one step further…it’s also about configuring the network.
Rene
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### Author:  [@puru.ibminfo](https://forum.networklessons.com/u/puru.ibminfo)
#### Post date: [May 9, 2016, 3:40am UTC](https://forum.networklessons.com/t/introduction-to-oer-optimized-edge-routing/962/5 "2016-05-09T03:40:17Z")
Hi Rene,
Any plans to do a topic on Pfr version 3 or IWAN?
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### Author:  [@ReneMolenaar](https://forum.networklessons.com/u/ReneMolenaar)
#### Post date: [May 9, 2016, 2:12pm UTC](https://forum.networklessons.com/t/introduction-to-oer-optimized-edge-routing/962/6 "2016-05-09T14:12:56Z")
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.
Rene
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### Author:  [@puru.ibminfo](https://forum.networklessons.com/u/puru.ibminfo)
#### Post date: [May 10, 2016, 6:00am UTC](https://forum.networklessons.com/t/introduction-to-oer-optimized-edge-routing/962/7 "2016-05-10T06:00:24Z")
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.
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### Author:  [@p.andi](https://forum.networklessons.com/u/p.andi)
#### Post date: [October 29, 2017, 4:44pm UTC](https://forum.networklessons.com/t/introduction-to-oer-optimized-edge-routing/962/8 "2017-10-29T16:44:57Z")
Hi Rene,
are there any update about the PfR material? i am currently preparing for the written and that would be helpful.
Thank you.
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### Author:  [@ReneMolenaar](https://forum.networklessons.com/u/ReneMolenaar)
#### Post date: [November 10, 2017, 11:27am UTC](https://forum.networklessons.com/t/introduction-to-oer-optimized-edge-routing/962/9 "2017-11-10T11:27:39Z")
Hi Andrea,
Not yet but it’s on the list.
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### Author:  [@syncope988](https://forum.networklessons.com/u/syncope988)
#### Post date: [March 18, 2019, 12:17am UTC](https://forum.networklessons.com/t/introduction-to-oer-optimized-edge-routing/962/10 "2019-03-18T00:17:32Z")
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
Regards
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### Author:  [@lagapidis](https://forum.networklessons.com/u/lagapidis)
#### Post date: [March 20, 2019, 4:00pm UTC](https://forum.networklessons.com/t/introduction-to-oer-optimized-edge-routing/962/11 "2019-03-20T16:00:02Z")
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 within Cisco documentation. However, strictly speaking, when CEF is enabled, the mechanism it uses to send packets over multiple paths is load sharing. It uses algorithms that share the load (based on flows, or specific source and destination addresses) but not necessarily equally like it would with OSPF without CEF.
The following documentaiton may be helpful in further clearing this up. However, be aware of how the terms load balancing and load sharing are used.
> **[Troubleshooting Load Balancing Over Parallel Links Using Cisco Express...](https://www.cisco.com/c/en/us/support/docs/ip/express-forwarding-cef/18285-loadbal-cef.html)**
>
> This document clarifies how Cisco IOS? Software implements Layer 3 load balancing across multiple parallel links when using Cisco Express Forwarding.
I hope this has been helpful!
Laz
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### Author:  [@ssaragusa](https://forum.networklessons.com/u/ssaragusa)
#### Post date: [November 17, 2019, 4:22am UTC](https://forum.networklessons.com/t/introduction-to-oer-optimized-edge-routing/962/12 "2019-11-17T04:22:52Z")
In this lesson, I believe this is a typographical error:
> For example OSPF will prefer a gigabit **OER has been renamed to** link over a FastEthernet link
where the text to which I added boldfacing, I do not believe should exist in this sentence.
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### Author:  [@ReneMolenaar](https://forum.networklessons.com/u/ReneMolenaar)
#### Post date: [December 2, 2019, 12:06pm UTC](https://forum.networklessons.com/t/introduction-to-oer-optimized-edge-routing/962/13 "2019-12-02T12:06:49Z")
Thank you Siobhan, just fixed this error.