Questions about anycasting setup

Bill Woodcock woody at pch.net
Fri Mar 9 00:54:32 CST 2012


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Hello, Anurag.

On Mar 8, 2012, at 9:51 PM, Anurag Bhatia wrote:
>   1. For anycasting does announcing a /24 from different ASNs (of
>   different datacenters) makes sense or it will be an issue to have a block
>   being announced from different ASNs?

Keeping a consistent announcing ASN for your prefix is thought to be best-practice, and if you don't do so, eventually there will be people who will undoubtedly complain, but there is no technical difficulty with announcing your same prefix from multiple origin ASNs.  Any difficulties you encounter will be because of people aggressively filtering what they choose to listen to.

>   2. We plan to use this anycasting based setup for DNS during initial few
>   months. Assuming low traffic for DNS say ~10Mbps on average (on 100Mbps
>   port) and transit from just single network (datacenter itself) - is this
>   setup OK for simple software based BGP like Quagga or Bird? 

Yes, and in fact, that's how nearly all large production anycast networks are built…  Each anycast instance contains its own BGP speaker, which announces its service prefix to adjacent BGP-speaking routers, whether those be your own, or your transit-provider's.  Doing exactly as you describe is, in fact, best-practice.

>   3. IPv6! - Is /32 is standard? We have only one /32
>   allocation from ARIN and thus if using /32 seems like hard deal - we have
>   to likely get another /32 just for anycasting? or we can use /48 without
>   issues? Also, is /48 a good number for breaking /32 so that we can do /48
>   announcements from different datacenters in simple uni casting setup?

A /48 is quite reasonable.  Announcing a whole /32 just for your anycast service would be wasteful.

Good luck!

                                -Bill




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