Troubleshooting BGP Neighbor Adjacency

(Rene Molenaar) #1

This topic is to discuss the following lesson:

(Hamood R) #2

Rene,

Great lesson.

Thanks

Hamood

(Marty S) #3

Thank you Rene!

How easy is to find if you have a duplicate AS number. I am referring to the AS private ranges?

Best,
MS/

(Rene Molenaar) #4

Hi Marty,

You can debug it on the router, it will tell you that an update is refused since it sees its own AS number in the path. Here’s an example:

Rene

(Shannon S) #5

Hi Rene,

Did you mean iBGP instead of eBGP?

Problem solved! The only difference with EBGP is that we don’t have to change the TTL with the ebgp-multihop command.

Rgds,

Shannon

(Ajay Krishna M) #6

Hi Rene,

How we can increase the BGP convergence time. can you please explain in brief.

Thanks,
Ajay

(Andrew P) #7

@Shannon
Problem solved! The only difference with EBGP is that we don’t have to change the TTL with the ebgp-multihop command

This is correct as written, because in the context of the paragraph, Rene is talking about iBGP. So written another way, it would read, “iBGP’s difference with EBGP is that we don’t have to change the TTL with the ebgp-multihop command” which is a true statement.

(Andrew P) #8

@Shannon
Good catch on the repeating lines. I will ask Rene to fix.

(Shannon S) #9

Hi Andrew,

Many thanks for the response!

I’ll have to re-read the notes on the lesson again to better understand your response. Bit murky still. Not to worry, this is on me to figure out first.

Rgds,

Shannon

(Rene Molenaar) #10

@Ajay

There are quite some different things you can do to increase the BGP convergence time. Is there anything in particular you want to know or just a general overview?

Rene

(Rene Molenaar) #11

@Shannon thanks for reporting the typo, it has been fixed.

(Shannon S) #12

Hi Rene,

Noted with thanks!

Rgds,

Shannon

(Ajay Krishna M) #13

Hi Rene,

I need general overview of increasing the BGP convergence time.

Regards,
Ajay

(Lazaros Agapides) #14

Hello Ajay!

At the moment we don’t have a section covering BGP convergence timers and tuning, but INE has a great blog post about it that you can find here:

http://blog.ine.com/2010/11/22/understanding-bgp-convergence/

I hope this is helpful!

Laz

(HARSHAVARDHAN R B) #15

Hello Rene,

Could you please tell me why a router cannot have two BGP autonomous systems configured ?

Thanks,
Harsha.

(Lazaros Agapides) #16

Hello Harsha

By design, BGP is made so that each router belongs to a single AS. But this doesn’t limit its functionality. You can still peer with routers from multiple AS as well as to routers in the same AS. There is however a way to allow a router to appear to neighbors to be a member of a second AS using what is called the Local-AS feature. This is usually done for migrations when moving from one ISP to another, or from one MPLS provider to another, and is usually provided as a temporary solution during the migration process.

BGP is designed to function with only a single AS assigned to each router.

I hope this has been helpful!

Laz

(HARSHAVARDHAN R B) #17

Hello Laz,

           Thank you so much for the reply. I appreciate the help. 

Thanks,
Harsha.

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