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New Member

6509 routing BGP

I am starting with 6509 running BGP:

I have configured a few comands in order to have bgp on, something like this:

router bgp 10                                                                  

no synchronization                                                            

bgp log-neighbor-changes                                                      

network my-network-ip                                                            

neighbor as-30-ip remote-as 30                                            

neighbor as-20-ip remote-as 20                                          

auto-summary

Is this enough ?

Rosa

1 ACCEPTED SOLUTION

Accepted Solutions
Hall of Fame Super Silver

6509 routing BGP

Rosa

If it is important that your AS not be a transit AS then you should configure an AS Path List and apply it outbound to both neighbors. The AS Path List would permit advertisement only of prefixes that originate from your AS.

Balancing traffic when you use BGP can get complex. I would suggest that it helps to think of it as two separate parts: 1) how to balance outbound traffic (traffic that you send to others) and 2) how to balance inbound traffic (traffic that others send to you.

There are several possibilities of how to balance outbound traffic and they have to do with how you learn routes and what you put into your routing table. Many providers give you a choice of what they will advertise to you. The choices may include advertising only a default route, advertising prefixes that originate in their AS (and perhaps prefixes that originate in AS that is directly connected to them), or advertising a larger set of routes, or advertising the complete Internet set of prefixes. So one possibility might be to have the provider in  AS30 adverttise their originated prefixes and to have the provider in AS20 send you a default route. That way you would send some traffic to AS30 but most traffic would go to AS20. There are other options where you would learn sets of prefixes from both providers and you would configure filters on the advertisements choosing to learn some prefixes from 20 and to learn other prefixes from 30.

Balancing inbound traffic is a bit more difficult. Some people balance traffic by advertising some of their prefixes to one provider and advertising other prefixes to the second provider. Some people balance traffic by prepending their AS number on advertisements to the less desirable provider.

I would also suggest that given the difference between 100 Mb and 10 Mb that some people would not try to balance traffic but would set up BGP so that there is a primary/referred path and a backup path that is used only when the primary path is not working.

HTH

Rick

4 REPLIES
Hall of Fame Super Silver

6509 routing BGP

Rosa

You have not told us what your environment is and what your expectations are. If you are doing this in a lab/test situation would be one thing and if you are attempting to configure a live router in a production network it is something different.

What you have posted is enough to get you started and probably enough to form neighbor relationships. I would suggest that there are some other things that you probably want to do. With neighbor20 and neighbor30 you have two neighbors whose AS is different from yours. So you will have 2 EBGP neighbors. You will learn some routes from neighbor20. And once you have learned routes you will advertise them to neighbor30. This means that traffic from neighbor20 (and anyone connected to neighbor20) may use your network as a transit path to get to neighbor30 (or someone connected to neighbor30). Is that what you want? If that is not what you want then you need to configure some filtering that will prevent advertising to neighbor30 what you learned from neighbor20.

HTH

Rick

New Member

6509 routing BGP

Thanks Rick for your answer.

This is my problem:

My domain is not intended to be a transit AS.

In fact, it is very important to prevent undesirable traffic.

I am wondering how to balance traffic betwen 100M/10M links.

Can you help me ?

Regards

Rosa

Hall of Fame Super Silver

6509 routing BGP

Rosa

If it is important that your AS not be a transit AS then you should configure an AS Path List and apply it outbound to both neighbors. The AS Path List would permit advertisement only of prefixes that originate from your AS.

Balancing traffic when you use BGP can get complex. I would suggest that it helps to think of it as two separate parts: 1) how to balance outbound traffic (traffic that you send to others) and 2) how to balance inbound traffic (traffic that others send to you.

There are several possibilities of how to balance outbound traffic and they have to do with how you learn routes and what you put into your routing table. Many providers give you a choice of what they will advertise to you. The choices may include advertising only a default route, advertising prefixes that originate in their AS (and perhaps prefixes that originate in AS that is directly connected to them), or advertising a larger set of routes, or advertising the complete Internet set of prefixes. So one possibility might be to have the provider in  AS30 adverttise their originated prefixes and to have the provider in AS20 send you a default route. That way you would send some traffic to AS30 but most traffic would go to AS20. There are other options where you would learn sets of prefixes from both providers and you would configure filters on the advertisements choosing to learn some prefixes from 20 and to learn other prefixes from 30.

Balancing inbound traffic is a bit more difficult. Some people balance traffic by advertising some of their prefixes to one provider and advertising other prefixes to the second provider. Some people balance traffic by prepending their AS number on advertisements to the less desirable provider.

I would also suggest that given the difference between 100 Mb and 10 Mb that some people would not try to balance traffic but would set up BGP so that there is a primary/referred path and a backup path that is used only when the primary path is not working.

HTH

Rick

New Member

6509 routing BGP

Thanks Rick.

I will try to put all together.

Perhaps I will be back (I am concerned that it means a lot of troubles     )

Regards,

Rosa

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