In article <mailman.58.1330527041.63724.bind-us...@lists.isc.org>, Oliver Garraux <oli...@g.garraux.net> wrote:
> On Wed, Feb 29, 2012 at 8:33 AM, takizo <paul...@takizo.com> wrote: > > Ju, > > > > What do you mean on more than one address? > > > > -- > > Paul Ooi > > > > > > > > On Feb 29, 2012, at 11:55 AM, ju wusuo wrote: > > > > Have seen some anycast DNS implementations using more than one address, some > > times even on the same subnet, any considerations or reasons for doing > > that? > > > > > > I assume he's asking why Google has 8.8.8.8 and 8.8.4.4, and why > whoever runs 4.2.2.2 has 4.2.2.1, 4.2.2.2, etc. I don't have an > answer. They may have to announce at least a /24 for BGP peers to > accept the routes. But 8.8.8.8 and 8.8.4.4 aren't in the same /24, so > that doesn't make sense there. The difference is that Google is running a public DNS, while Level(3) is an ISP and their DNS was intended just for their customers (allowing public access is mostly a legacy of inheriting these servers from Genuity, nee BBN Planet -- we never had a central database of all customer address blocks from which to formulate an ACL). So Google has to be concerned about having diverse routes from many different ISPs, and announcing two /24's facilitates this. Level(3) is only concerned with routing within their network, and their OSPF routing can achieve diversity at the /32 level. -- Barry Margolin Arlington, MA _______________________________________________ Please visit https://lists.isc.org/mailman/listinfo/bind-users to unsubscribe from this list bind-users mailing list bind-users@lists.isc.org https://lists.isc.org/mailman/listinfo/bind-users
