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Beginner

Redistribution between two BGP Peers with SAME AS number

Hello All,

 

We want to redistribute received routes from one provider e.g. SingTel to Telstra. Both been configured as same AS and peered with BGP.

 

We are receiving route from SingTel e.g. 10.80.128.0/24 (Asia office subnet) and Telstra (Asia office not with Telstra) does not have that route in its BGP table. Both ISP connected to same CE WAN router. We want that route in Telstra BGP table as well. So our remote site can reach singtel routes as well via Telstra gateway. 

Both are our MPLS provider.

 

I have attached diagram of this. 

 

Any ideas for what I might need to do to get this working..?

Any thoughts or suggestions would be greatly appreciated!

Thanks in Advance,
Jeet

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Accepted Solutions
VIP Advisor

Re: Redistribution between two BGP Peers with SAME AS number

Hello

As I said by default bgp loop prevention will not allow any prefix with its own ASN in the path attitude to be allowed so to negate this try the following:

 

On the Teltra rtr towards its bgp neighbour facing ASN64800

neighbor xxxx allowas-in


Then do a soft RR  (clear ip bgp xxx soft in ) and test again 



kind regards
Paul

Please rate and mark posts accordingly if you have found any of the information provided useful.
It will hopefully assist others with similar issues in the future
9 REPLIES 9
VIP Mentor

Re: Redistribution between two BGP Peers with SAME AS number

Hello,

 

--> Both ISP connected to same CE WAN router.

 

Post the full configs of all routers that are under your control...

Beginner

Re: Redistribution between two BGP Peers with SAME AS number

Correct both routers are connected to SAME WAN router.

Highlighted
Beginner

Re: Redistribution between two BGP Peers with SAME AS number

Hi,

Could you redistribute the route from Telstra to Singtel using "aggregate-address" without "as-set"? So Singtel will not learn the AS number of Telstra?

route bgp xxx
aggregate-address 10.80.32.0 255.255.254.0 summary-only

I didn't test it, please check if it work or not.
Beginner

Re: Redistribution between two BGP Peers with SAME AS number

Hi ngkin2010,

 

Those routes already there in Singtel but what I want is other way around.

 

Those are Singtel received routes , I want to redistribute to Telstra. and Both have same AS number. and both connected to same WAN router.

 

Jit

VIP Advisor

Re: Redistribution between two BGP Peers with SAME AS number

Hello

No so sure I understand - You have a single wan rtr  connected to two ISPs and your receiving an ebgp route from one these ISP's that isnt reachable from where -  What your topology shows is one router AS64800 (I assume your wan router) connected to two ISP rtrs in the same ASN so why would you want to your wan rtr to be a transit path between two ISP's

 

You should ONLY advertise locally originated prefixes towards your ISP's NEVER other ISP routes, in fact I doubt they would even allow them in anyway.

 

Lastly by default bgp wont accept routes originated from its own ASN



kind regards
Paul

Please rate and mark posts accordingly if you have found any of the information provided useful.
It will hopefully assist others with similar issues in the future
Beginner

Re: Redistribution between two BGP Peers with SAME AS number

Hi Paul,

 

I have added my topology here. We were with Singtel and disconnected all Singtel across APAC region. Singapore where the router is , have Telstra and Singtel as Transit to reach to Asia offices. Offices in Asia still have Singtel not migrating to Telstra.

 

I still have single link between Melbourne and Singapore that I am going to disconnect. That's where the problem will start, when I will disconnect that I can reach up to Singapore via Telstra as both on Telstra. But I wont be able to reach our offices in Asia from Melbourne. 

 

 

VIP Advisor

Re: Redistribution between two BGP Peers with SAME AS number

Hello

As I said by default bgp loop prevention will not allow any prefix with its own ASN in the path attitude to be allowed so to negate this try the following:

 

On the Teltra rtr towards its bgp neighbour facing ASN64800

neighbor xxxx allowas-in


Then do a soft RR  (clear ip bgp xxx soft in ) and test again 



kind regards
Paul

Please rate and mark posts accordingly if you have found any of the information provided useful.
It will hopefully assist others with similar issues in the future
Beginner

Re: Redistribution between two BGP Peers with SAME AS number

Hi Paul,

 

I will try that and get back to you..

 

Thanks,

 

Jit

Beginner

Re: Redistribution between two BGP Peers with SAME AS number

Hi Paul,

This has fixed the issue.

 

Thank you.

Jit

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