[dns-operations] fcc.gov has two name servers with MTU issues

[Stephane Bortzmeyer]

[Yes, problems should be reported to the zone manager first. In that
case, the listed address gets a "<dns-admin at fcc.gov>: host
dc-ip-2.fcc.gov[192.104.54.91] said: 550 #5.1.0 Address rejected. (in
reply to RCPT TO command)"]

ns3.fcc.gov and ns4.fcc.gov (but not the other two) time out when
queried with the default EDNS buffer size, 4096. Without EDNS, or with
smaller buffer sizes, it works. tcpdump shows that the response with
the smaller buffer size first the Ethernet MTU, but not if you
increase the size:

% dig +bufsize=1692 @208.31.254.132 SOA fcc.gov

; <<>> DiG 9.9.2-P2 <<>> +bufsize=1695 @208.31.254.132 SOA fcc.gov
; (1 server found)
;; global options: +cmd
;; connection timed out; no servers could be reached

 dig +bufsize=1691 @208.31.254.132 SOA fcc.gov

; <<>> DiG 9.9.2-P2 <<>> +bufsize=1691 @208.31.254.132 SOA fcc.gov
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 48845
;; flags: qr aa rd; QUERY: 1, ANSWER: 2, AUTHORITY: 5, ADDITIONAL: 7
;; WARNING: recursion requested but not available

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags: do; udp: 4096
;; QUESTION SECTION:
;fcc.gov. IN SOA

;; ANSWER SECTION:
fcc.gov. 300 IN SOA ns.fcc.gov. dns-admin.fcc.gov. (
2014010101 ; serial
1800 ; refresh (30 minutes)
3600 ; retry (1 hour)
2419200 ; expire (4 weeks)
300 ; minimum (5 minutes)
)
...
;; Query time: 194 msec
;; SERVER: 208.31.254.132#53(208.31.254.132)
;; WHEN: Mon Jan 6 15:14:09 2014
;; MSG SIZE rcvd: 1397