In a message written on Mon, Feb 04, 2008 at 07:50:50PM -0500, Kevin Loch wrote:
There is an interesting variation in what records are returned for a standard 512 byte request (dig ns . @[x].root-servers.net):
A,C,D,E,F,G,I,J: return the same 10 A records and 4 AAAA records in the same order every time. They never return A records for K,L,M and never get AAAA records for K,M.
B: returns all 13 A records in random order and then two AAAA records in random order. This allows all records to be returned with equal weight within each record type.
H,K,L,M: return all 13 A records in static order and then A and F AAAA records so H,J,K,M AAAA records are never returned.
Tested with dig 9.4.1-p1 on a v6 enabled system.
I concur. An interesting thing I noticed that doesn't really cause an operational problem but may confuse some people is their behavior is also quite different when queried for "any". If your a lazy admin like me who is used to typing "dig any foo" for testing you may try "dig any . @[a-m].root-servers.net." When I do that, I get the following response: a, c, d e, f, g, i and j return 1 SOA, 8 A, and 3 AAAA's (the first 3). b, h, l, k, and m return 1 SOA, 13 A, no AAAA records. If you make this mistake you might think b, h, l, k and m have no IPv6 data, which is wrong. Querying with NS (as nameserver would do) clearly shows that. While a cosmetic problem, I fear it may confuse a number of admins as the troubleshoot problems in the near future. -- Leo Bicknell - bicknell@ufp.org - CCIE 3440 PGP keys at http://www.ufp.org/~bicknell/