Weird DNS Problems

[Simon Hobson]

D McDonald wrote:

>About a week ago we switched the DNS server of our domain 
>saturncorp.com to ns.saturncorp.com. It's a redhat
>machine running bind 9.2.3. However it now seems that on some DNS 
>servers are unable to resolve some addresses.
>For example on one isp www.saturncorp.com works fine (non-auth), but 
>ftp.saturncorp.com doesnt work. It appears
>that some of these servers are running on cache alone, im not sure. 
>This is only the second BIND server ive set
>up, and the first was a internal server.

There is some confusion :

$ dig @e.gtld-servers.net saturncorp.com ns

; <<>> DiG 9.2.2 <<>> @e.gtld-servers.net saturncorp.com ns
;; global options:  printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 60437
;; flags: qr rd; QUERY: 1, ANSWER: 3, AUTHORITY: 0, ADDITIONAL: 3

;; QUESTION SECTION:
;saturncorp.com.                        IN      NS

;; ANSWER SECTION:
saturncorp.com.         172800  IN      NS      cbru.br.ns.els-gms.att.net.
saturncorp.com.         172800  IN      NS      cmtu.mt.ns.els-gms.att.net.
saturncorp.com.         172800  IN      NS      ns.saturncorp.com.

;; ADDITIONAL SECTION:
cbru.br.ns.els-gms.att.net. 172800 IN   A       199.191.128.105
cmtu.mt.ns.els-gms.att.net. 172800 IN   A       12.127.16.69
ns.saturncorp.com.      172800  IN      A       12.23.213.25

;; Query time: 178 msec
;; SERVER: 192.12.94.30#53(e.gtld-servers.net)
;; WHEN: Wed Dec 15 12:19:13 2004
;; MSG SIZE  rcvd: 159

$ dig @12.23.213.25 saturncorp.com ns

; <<>> DiG 9.2.2 <<>> @12.23.213.25 saturncorp.com ns
;; global options:  printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 24412
;; flags: qr aa rd; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;saturncorp.com.                        IN      NS

;; ANSWER SECTION:
saturncorp.com.         43200   IN      NS      12.23.213.25.saturncorp.com.

;; Query time: 130 msec
;; SERVER: 12.23.213.25#53(12.23.213.25)
;; WHEN: Wed Dec 15 12:19:21 2004
;; MSG SIZE  rcvd: 59

$ dig @12.127.16.69 saturncorp.com ns

; <<>> DiG 9.2.2 <<>> @12.127.16.69 saturncorp.com ns
;; global options:  printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 33078
;; flags: qr aa rd; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 2

;; QUESTION SECTION:
;saturncorp.com.                        IN      NS

;; ANSWER SECTION:
saturncorp.com.         3600    IN      NS      cbru.br.ns.els-gms.att.net.
saturncorp.com.         3600    IN      NS      cmtu.mt.ns.els-gms.att.net.

;; ADDITIONAL SECTION:
cbru.br.ns.els-gms.att.net. 86400 IN    A       199.191.128.105
cmtu.mt.ns.els-gms.att.net. 86400 IN    A       12.127.16.69

;; Query time: 125 msec
;; SERVER: 12.127.16.69#53(12.127.16.69)
;; WHEN: Wed Dec 15 12:19:26 2004
;; MSG SIZE  rcvd: 126


It looks like the root nameservers are listing three servers as 
handling your domain - and two of those are claiming to be the only 
ones handling it.

So what happens is down to luck, ie which nameserver happens to get used.

You need to get cbru.br.ns.els-gms.att.net. and 
cmtu.mt.ns.els-gms.att.net. either removed as nameservers for your 
domain in the root zone, or get them sorted so they give the same 
information out as your server.

However, IIRC, they won't let you list just one server.

Simon

-- 

NOTE: This is a throw-away email address which will reach me for as 
long as it stays spam-free, remove date for real address.

Simon Hobson MA MIEE, Technology Specialist
Colony Gift Corporation Limited
Lindal in Furness, Ulverston, Cumbria, LA12 0LD
Tel 01229 461100, Fax 01229 461101

Registered in England No. 1499611
Regd. Office : 100 New Bridge Street, London, EC4V 6JA.