bgp question

[Reignman]

Hello All!

first of all I would like to say that my knowledge in Cisco equipment is very limited, so please bear with me.
We have a connection to two ISPs (2Mbps each) and use one of them as primary (using higher local preference).
I would like to know if it's possible to receive traffic from specific AS numbers to the second one overriding the first one.
The equipment is a Cisco 3640.

Thank you all in advance

 

[tschouten]

I'm not sure I understand the question quite correctly. So let me break it down a little further and you point out where I go wrong in understanding the question.

If I gather you right you are saying that AS-xxx is taking precedence over AS-yyy?

For example, serial0 is conected to BGP_AS-xxx and serial1 is connected to BGP_AS-yyy.
And all you see is routing tables for AS-xxx?

Or are you asking if you can make AS-xxx be prefered over AS-yyy? (You would use CAR Comitted Access Rates to acheive this, yes it is possible)

If none of what I said makes sense or even lands remotely to what you asked help me out and give me some more information.

 

[Reignman]

tschouten thank you very much for your reply.
I believe you're right. I didn't explain very much what I want to do.
The situation is more or less something like this.
True we have two connections with two ISPs (AS-xxx and AS-yyy). AS-xxx has better peerings with almost everyone and the roundtrip is much much better than AS-yyy. As you understand almost everyone prefers AS-xxx which makes things a little difficult. A good way to "fix" this is by announcing some of our Class C's (we have our own address space) mainly from AS-xxx and the remaining from AS-yyy. However this is an option that I don't have for the moment
What I would like to do is find some way to alter??? the route of the traffic originating from some of our customers (AS-zzz and AS-aaa) to use AS-yyy instead of AS-xxx (temporary solution).
I hope I helped you in understanding my intentions.
Thank you very much!

 

[tschouten]

Ahhhhhhh

I understand perfectly what you want to do now. You should look into CAR (comitted access rates). Or perhaps BGP-policy ip-prec-map (which is a bgp policy map based on ip precedence).

You want to say if from block1 of addresses use AS-xxx if from block2 of addresses use AS-yyy. Or something to that nature just using generic terms here.

This location would be a good place for you to start. Look at the BGP-Policy section.

http://www.cisco.com/en/US/products...ommand_reference_chapter09186a0080087da7.html

 

[Reignman]

Thank you once more for the immediate response!
This is a very good way to do what I want (I think even better from what I had in mind), but as soon as the blocks are defined more clearly (I'm still waiting on this), so until then I would like something like this...
AS-aaa sends to me some IP traffic (voice and data). Naturally AS-xxx (ISP with the best peerings) will take over.. Instead of this, I would like AS-yyy to take over only for him!
I want to be able to do AS based (origin) routing.
Can this be done?

 

[tschouten]

Something fuzzy in the back of my mind is saying yes, to a certain extent. But I'm having a hard time thinking of how to do it besides changing/using BGP Community Values.

 

[tschouten]

I'll think about it and see what I can come up with but if you want you can look at what using Community Values can do for you here.

http://www.cisco.com/en/US/products...ommand_reference_chapter09186a0080087da7.html

I know I refer to cisco website a lot it's easier than trying to type out what they have listed already, besides I can blame the website that way when I'm wrong...

 

[Reignman]

What do you think about match as-path ???
Could it be the solution to what I want?

 

[tschouten]

That was exactly what I was trying to think of, it acts in the same nature as an access list.

There are a ton of ways you can force routing policies in BGP. You can do just about anything with it, one reason I love it. Also why I hate it because it can get bogged down with a lot well which is best and what the heck do I do this time questions???

 

[Reignman]

Unless you have something else to recommend I think it's a good way to proceed...
Can you think of what I need to do in order to proceed?
In any case it's late here (Greece) and I should try getting some sleep if I want to do things correctly tomorrow

 

[tschouten]

lol, I do believe you have to have IP CEF enabled other than that it is like an access list. I've been working all day and haven't slept much in the last few days so I know what you mean. Can't think of anything else you may need to know. If you run into problems let me know.

tschouten@weltman.com

Greece (beautiful place, loved it when I visited there)