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IngGerardo013
Beginner

Difference between weight and med bgp atributes

Hello guys,

I am a little confused about weight and MED bgp atributes , so far I know the following:

 

- Weitght is just used by Cisco products

- MED is the sixth tie breaker and the weight the 1st one

- Both influence the router to reach and specific prefix stablishing priority.

 

But I cannot clarify in my mind the key differences between these 2 atributes, any human explanation will be very apreciated, thank you!.

 

 

 

2 ACCEPTED SOLUTIONS

Accepted Solutions
Jon Marshall
Hall of Fame Guru

 

They do different things. 

 

Weight is used to influence traffic outbound from your AS ie. you apply weight to routes you receive from other ASs.

 

MED is used to influence traffic inbound to your AS ie. you apply MED to routes you advertise to a neighboring AS. 

 

Jon

View solution in original post

Richard Burts
Hall of Fame Guru

Probably the most important difference between weight and MED is that you apply weight to advertisements from a neighbor (and that weight is not known on any other router). And every routing decision you make on how to forward packets is controlled by the configured weight. So you set the weight and your routing decisions are controlled by that weight. With MED you can set the attribute on what you advertise to a neighbor to attempt to influence their routing decision or the neighbor might set the attribute on advertisements sent to you to try to influence your routing decision. So the attribute MED is influencing routing decisions on neighbors different from the one who set the attribute.

 

HTH

 

Rick

HTH

Rick

View solution in original post

4 REPLIES 4
Jon Marshall
Hall of Fame Guru

 

They do different things. 

 

Weight is used to influence traffic outbound from your AS ie. you apply weight to routes you receive from other ASs.

 

MED is used to influence traffic inbound to your AS ie. you apply MED to routes you advertise to a neighboring AS. 

 

Jon

View solution in original post

Thank you guys! sometimes books and articules does not explain/clarify from what perspective are explaining the concept , that is the reason sometimes concepts are little hard to understand , now with your easy explanation evrything is clear, again thank you!!

You are welcome. I agree that sometimes reading books and articles may leave some concepts not so clear. This community is an excellent place to get clarification of those concepts. Glad we were able to be of help.

 

HTH

 

Rick

HTH

Rick
Richard Burts
Hall of Fame Guru

Probably the most important difference between weight and MED is that you apply weight to advertisements from a neighbor (and that weight is not known on any other router). And every routing decision you make on how to forward packets is controlled by the configured weight. So you set the weight and your routing decisions are controlled by that weight. With MED you can set the attribute on what you advertise to a neighbor to attempt to influence their routing decision or the neighbor might set the attribute on advertisements sent to you to try to influence your routing decision. So the attribute MED is influencing routing decisions on neighbors different from the one who set the attribute.

 

HTH

 

Rick

HTH

Rick

View solution in original post