[AusNOG] dual home - set one carrier to secondary with AS prepend - not working

Mon Dec 21 15:28:23 EST 2015

In response to a specific comment you made in your original post... " Using the looking glass tools, it looks like places like iinet are learning networks only via nextgen."

The looking glasses are peering with routers that have already made their best path decision, therefore those routers are only advertising their best selected path to the looking glass. So in the case of the iiNet looking glass, the routers have already made best path selection between the Telstra and Nextgen received routes, Nextgen received routes won and is what is then advertised to the LG.

Looking glasses are only meant to present information on how that AS routes to your prefixes at that very point in time, all best paths by the actual routers forwarding traffic have been calculated and what you are seeing is the end result. So the results you are seeing are normal.

Specific to your situation, a lot of Australia will be preferring to send you traffic via Nextgen as they peer at IX's - it's cheaper than sending the traffic to you through a "Gang of Four" (GoF) company, i.e. Telstra, who don't. The only way you're going to be able to "fix" this is as per an earlier suggestion - advertise an aggregate via Nextgen and longer prefixes via Telstra. Best path selection algorithms won't even come into play then as longest prefix always wins.

Cheers,
Nik.

-----Original Message-----
From: AusNOG [mailto:ausnog-bounces at lists.ausnog.net] On Behalf Of Mitchell, Peter
Sent: Monday, 21 December 2015 2:14 PM
To: AusNOG at lists.ausnog.net
Subject: Re: [AusNOG] dual home - set one carrier to secondary with AS prepend - not working

Thanks all for responses.  We are in change freeze so it is difficult to test failover.

Two of the /24's are part of a /23.  I will investigate sending different masks to different carriers as suggested.  

Appreciate everyone's assistance.

Peter.

From: Ben Hohnke [mailto:settra+ausnog at gmail.com]
Sent: Monday, 21 December 2015 1:00 PM
To: Mitchell, Peter; AusNOG at lists.ausnog.net
Subject: Re: [AusNOG] dual home - set one carrier to secondary with AS prepend - not working

Is tearing down the nextgen session for testing a possibility? That way you'd be able to find out if Telstra are advertising your prefixes correctly.
Also, does the looking glass results show the AS prepending correctly?
Ben

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