On 2010-02-14, at 17:43, Mark Andrews <marka@isc.org> wrote:
Using three consecutive addresses doesn't remove single points of failure in the routing system.
That depends on how the routes for those destinations are chosen, and what routing system you're talking about. For distribution of a service using anycast inside a single AS, and with one route per service, it makes no difference whether the addresses are adjacent. Two /24 routes are no more stable than two /32 routes within an IGP. There's no prefix filtering convention to accommodate, here.
If their goal is distribute a service for the benefit of their own = customers, then keeping all anycast nodes associated with that service = on-net seems entirely sensible.
Which only helps if *all* customers of those servers are also on net.
Whether it helps depends on what Level3's goals are. This is not public infrastructure; this is a service operated by a commercial company. For what it's worth, I have never heard of an ISP, big or small, deciding to place resolvers used by their customers in someone else's network. Perhaps I just need to get out more. Joe