One of my former employers backhauled all their legacy nameservers to a = single site, eg: e[0-2].ns.voyager.net.
While they were originally on diverse subnets and geographical = locations, this appears to have changed.
As one of the people who originally worked on that setup, I'll note that they're all being announced by 7321, which is certainly not the ideal for purposes of diversity, but I notice some variation in the ping times, so it's not clear to me that there's a reliable basis for expecting that they're not at least diverse geographically. The original locations were in Dayton, Kalamazoo, and New Berlin, all of which are several ms away from Chicago, and while several of the facilities have been shuffled around or closed, it's not clear that there aren't still nameservers in those states. AS diversity wasn't there for all that long to begin with; I seem to recall that a lot of it was being announced from 8011 as the integration efforts went on. It seems to me that for very small or very large organizations, there are significant benefits to finding AS diversity, but for mid-size ones, the picture is a bit less clear. In the Voyager case, the existence of separate networks was something that came along as more of a bonus and side effect of acquistions, and nameserver engineering took advantage of it, but network engineering's goal was to get all the networks integrated and connected, so eventually things got rolled into 8011. That would definitely count as somewhat suboptimal from the point of nameserver reliability, but the network grew generally more reliable since there weren't twenty slightly different ways of doing things and lots of legacy crud that neteng needed to "just know". While that did a lot to increase the overall reliability of the network, it certainly is putting your eggs all in one basket, and then you have to be ready for the hazards. We had, for example, this guy in Michigan who liked to load up routers in remote locations with unreleased versions of Cisco code that he'd get from his contacts at Cisco, which led to several cases of network downtime when they didn't work as expected (or at all). I believe that Wisconsin network engineering was generally fearful that one day it would turn ugly and something bad would happen that would take down the whole network; this is the downside to having less compartmentalization. ... JG -- Joe Greco - sol.net Network Services - Milwaukee, WI - http://www.sol.net "We call it the 'one bite at the apple' rule. Give me one chance [and] then I won't contact you again." - Direct Marketing Ass'n position on e-mail spam(CNN) With 24 million small businesses in the US alone, that's way too many apples.