ISC uses an unusual routing configuration for the F-Root name server. While the configuration is relatively easy to understand, it's hard to deduce by looking at the routing tables. We'll explain it here!
The network 192.5.4.0/23 is used for F-Root. The reasons for using this block are historical and unimportant, but the fact that it is a /23 is very important. Looking in the global routing table, you'll find 192.5.4.0/23 routed worldwide; ISC has obtained multiple transit providers for this network to provide excellent access to F-Root.
Something we're fortunate to have at ISC is the founders of some of the most influential Internet Exchanges (IXPs) amongst our senior staff. I haven't been personally involved in the IXP business for around 7 years now, so it was a pleasure to be invited as guest 
