Questions about anycasting setup

Anurag Bhatia me at
Thu Mar 8 23:51:16 CST 2012

Hello everyone.

I am working on creating a small anycasting based setup with 3-4 servers in
US. Plan is to use this for DNS and later for CDN setups. I have few
confusions in mind and was wondering if you guys here can put some light on

   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 and I should avoid and prefer having
   own router below datacenters network and eventually use one single ASN to
   announce the anycasting block?

   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? Certainly
   colocating routers will be slow & expensive. Does it offer any direct
   advantage in such simple setups?

   3. IPv6! - I am looking at possibility of having support of IPv6 in
   anycast right from start. Can't really find a good prefix size for
   anycasting announcement. I can see Hurricane Electric as well as Google
   using whole /32 block for IPv6. So 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?

I apologize for any wrong questions/logic - really new to this. Please
correct me if I am wrong on any concept.

Appreciate your help.



Anurag Bhatia
or simply - http://[2001:470:26:78f::5] if you are on IPv6 connected

Twitter: @anurag_bhatia <!/anurag_bhatia>

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