BGP MED Attribute

In networking, the BGP MED attribute is an important part of the routing process. But what is it, and why is it important? This post will explain the purpose of the MED attribute, and we'll also take a look at some common use cases for this powerful feature.

So if you're looking to learn more about BGP MED, you've come to the right place!

What is BGP MED Attribute?

The BGP MED attribute, also known as the Multi-Exit Discriminator, is a metric used by Border Gateway Protocol (BGP) to determine the best path for routing traffic between autonomous systems.

The value of the MED attribute can be set by network administrators, allowing for the customization of routing decisions. In addition to manually setting a value for the MED attribute, it can also be automatically propagated from one autonomous system to another. This allows for greater flexibility and adaptability in BGP routing decisions. Overall, the BGP MED attribute plays an important role in optimizing network traffic flow across multiple autonomous systems.

How is a MED Metric Advertised?

There are several rules to consider when a MED metric is advertised:

  • First and foremost, a more specific metric will cancel out a less specific one. For example, if you have two metrics of different groups, the group-specific metric takes precedence over the global BGP metric. Likewise, if you have peer-specific and other global metrics, the peer-specific metrics override both others.
  • A routing policy's metric definition takes priority over a metric-out statement.
  • Any defined metric will take precedence over a metric received from a route.
  • If a MED metric is not associated with a received route, and if a metric value is not configured, no metric is advertised. If you do not set a metric value, it will be automatically set to zero when advertising an active route.

BGP MED vs Local Preference

As we mentioned before, BGP MED, or Multi-exit Discriminator, is a BGP attribute that allows a network to inform its BGP neighbors about preferred entry points into the network.

Local Preference, on the other hand, is an attribute used to influence routes within a single BGP autonomous system. In other words, BGP MED influences which BGP neighbor a network will use to reach a destination, while Local Preference influences the choice of exit point within a particular network.

BGP MED can also be considered a more globally significant attribute, as it can influence routing decisions for all BGP neighbors, while Local Preference only affects choices made within one autonomous system. Both attributes are important in determining BGP routing decisions, but they serve different purposes and should not be confused with one another.

What are some common uses for BGP MED?

One common use case for BGP MED is when different ISPs connect to a provider through different points of presence with varying levels of available bandwidth. In this scenario, the provider could assign a higher BGP MED value to the slower PoPs to influence external peers to primarily use the higher bandwidth connections.

Another potential use case is for directing traffic towards specific data centers in cases where there are multiple options available within a geographical region. By assigning a lower BGP MED value to the preferred data center, external peers may be more likely to route traffic toward it. BGP MED should be used carefully, as it can lead to unbalanced traffic distribution and potential network congestion if not implemented properly.

Final Words

The BGP MED attribute is a useful tool for networking. By setting the MED value on your border gateway protocol (BGP) advertisements, you can tell other networks how highly you think they should route traffic to your network.

This could be helpful if you have multiple connections to different providers and want to make sure that traffic from one provider is routed through another provider’s network as efficiently as possible.

Have you tried using the BGP MED attribute in your own networking?

Before, you must to check our CCIE Enterprise Infrastructure course about BGP MED.

Created by
Stanley Avery

I am a certified network engineer with over 10 years of experience in the field. I have a deep understanding of networking and IT security, and I am always looking for new challenges.

View profile

Daniel Lardeux
Daniel Lardeux Senior Network Consultant at Post Telecom

I passed the CCDE Practical exam and Orhan’s CCDE course was very important contributor to my success. I attended the CCDE course of Orhan Ergun in July and it was exactly what I needed, Orhan is taking the pain to break down the different technologies.

Roy Lexmond
Roy Lexmond Senior Network Designer at Routz CCDE #20150017 & CCIE R&S; #26557

After I attended Orhan Ergun’s CCDE course I passed the CCDE practical exam.I really enjoyed the course a lot ...

Nicholas Russo
Nicholas Russo Network Consulting Engineer (CCDE/CCIEx2), Cisc

I signed up for Orhan’s CCDE training. This training is very technically detailed and the use-cases, quizzes, scenarios, and mind maps are all great resources in the overall training program. Orhan teaches his students to think like a network designer ...

Slide Heading
Slide Heading Network Systems Engineer at Conscia A/S CCIE #42544 (SP) & CCDE #20160015

Orhan is forcing you to take off the implementation hat that most of us have been wearing for many years, instead he is providing a new fancy design hat, which makes you see and deal with the issues presented ...

Kim Pedersen
Kim Pedersen CCIE in RS and SP (#29189) CCDE#20170021

I’ve used Orhan’s self-paced CCDE training material. If you are interested in knowing how all the technologies go together in a coherent design i can highly recommend it.I also enjoyed the Quizzes which helped pick out my weak spots in selecting ...

Laurent Metzger
Laurent Metzger 3xCCIE/CCDE Senior Network Architect

Hi Orhan. I passed the CCDE exam on February 22. I read everything that you put on your Self Paced CCDE Training course and it was very helpful in my success. Thank you very much.

Martin J. Duggan
Martin J. Duggan Network Architect at AT&T;, Ciscopress Author CCDE #20160006 & CCIE#7942

I attended Orhan’s April 201610 days CCDE Bootcamp. I am CCDE now !

You can tell Orhan has a great deal of experience, it really comes through when he presents his design case studies and the CCDE Practical scenarios.

Muhammad Abubakar
Muhammad Abubakar Lead Network Architect – CCDE #20160016 2xCCIE #26693 2xJNCIE VCIX

Your excellent CCDE materials and amazing Bootcamp helped me tremendously through my learning journey.Also thank you very much for being available whenever I have a design question or a complex design topics. I can’t compare your design skills ...

Jennifer Pai
Jennifer Pai Network/Security Engineer at KNET Technology

Thanks Orhan very much for this course. It helped strengthen my “Network design mind”.

Ruslan Silyayev
Ruslan Silyayev Solution Architect at R.I.S.K Company

Training by Orhan is not a CCDE preperation training only. It will be useful for engineers which are dealing with design. You want to pass CCDE exam or learn network design, then don’t look at anywhere else!

Sameer Meher
Sameer Meher Solutions Architect at 23 Wards/Japan

Orhan Ergun’s CCDE course was really very good. CCDE Level Intelligence was delivered very well and with very useful case studies and the scenarios, I am thankful to Orhan for all his help!

Ken Young
Ken Young Senior Technical Architect Province of Nova Scotia, 2xCCIE #41597 | CCDE #20170047

If anyone wants to understand network design and architecture, also pass CCDE exam , I recommend you to attend Orhan’s online courses! I am a CCDE now but learning is a journey, we will be together in your other courses too Orhan!

Matt Cross
Matt Cross Technical Architect at Heartland – CCDE #2019::7

Orhan did an excellent job of filling in the gaps of knowledge that I had that took me to the finish line of the practical exam CCDE. The community of people that Orhan facilitates are both engaging and supportive of the journey to CCDE. Orhan ...

Shiling Ding
Shiling Ding Sentinel Technologies – CCDE #2019::12

Just passed the CCDE Practical exam! I attended Orhan Ergun’s CCDE training program , used Orhan’s Instructor Led and Self-Paced CCDE training and Online CCDE Practical Scenarios during my CCDE journey. Orhan’s CCDE In Depth book is an excellent summary ...

Abelardo Basurto
Abelardo Basurto Solutions Architect at Cisco Systems – CCDE 2018::6

Hi everyone, I’ve just passed the CCDE Exam. My Number is CCDE 2018::6 I attended to Online CCDE Bootcamp of Orhan. I want to thank Orhan not only for the great book and bootcamp, but also for his commitment, availability and willingness to assist the ...

Hady Mohamed Abdellah
Hady Mohamed Abdellah Network Architect Hamad International Airport Qatar – CCDE 2018::1

Hi guys, I’m so happy that I passed the exam. I’ve already got my number CCDE 2018::1. Thanks to Orhan for being the best CCDE instructor in the world. I highly recomend Orhan’s CCDE Training and In-Depth-CCDE ...

Bryan Bartik
Bryan Bartik Sr. Systems Engineer at CompuNet – CCDE 20170059

Hi Orhan I passed CCDE Practical exam on November 2017 ! I really enjoyed your materials and quizzes and use cases. They were definitely helpful in my preparation. Thanks a lot !

Giedrius Trapkauskas
Giedrius Trapkauskas Network Solutions Architect at Liberty Global – CCDE 20180004

I attended Orhan’s CCDE Training in Istanbul and it was very helpful in my preparation. I passed the exam recently and I want to say Thank you Orhan! For those who want to pass the CCDE exam, definitely start with ...

Alaa Issa
Alaa Issa Sr.Solutions Architect – CCDE#20180033 3xCCIE ( Collab|DC|Security )#27146

I registered to Orhan’s training in Feb 2017. From that time, I attended Orhan’s training several times. The depth of knowledge which Orhan has is amazing, and how to present such consistent knowledge to the ...

Mazin Ahsan Design Lead Engineer | Solutions Engineer | CCDE License # 20160030 | CCIE Licence # 23892

I passed the CCDE Practical Lab exam on November 17,2016 from supplications of elders and dedication from my Sensei Mr. Orhan Ergun I took different CCDE bootcamps in the past. Orhan has the most depth and expertise ...

Jeff Patterson CCDE# 2018::11

Hi Orhan I wanted to pass along my appreciation for the outstanding training material. I used the online CCDE training provided by Orhan as well as the In-Depth-CCDE book and passed the exam in February 2018. Thank you Orhan!

Mehdi Sfar
Mehdi Sfar Network and Security Architect / CCDE #20210003 | CCIE R&S; #51583

I signed up for Orhan’s CCDE Self paced Course. This course, along with the CCDE In Depth book, helped me for my CCDE Practical as well as Written exams. It pushed me to ask the "WHY" questions and allowed ...

Related courses