Bind 9.4.2 not resolving one domain

[Hans F. Nordhaug]

* caio <elcaio at gmail.com> [2008-09-04]:
[cut]
> do not know if a connectivity problem, because i have 2 name servers, at 
> the same network level hierarchy (but differents subnet).., and maybe 
> there is one working ok while the other with failure..
> 
> here the case of the secondary ns...(at this moment):
> 
> # dig @dns2.mydomain.com www.yahoo.com.ar +trace
[cut]
> www.yahoo.com.ar.       1800    IN      CNAME   hp2.latam.g1.b.yahoo.com.
> g1.b.yahoo.com.         172800  IN      NS      yf1.yahoo.com.
> g1.b.yahoo.com.         172800  IN      NS      yf2.yahoo.com.
> g1.b.yahoo.com.         172800  IN      NS      yf3.yahoo.com.
> g1.b.yahoo.com.         172800  IN      NS      yf4.yahoo.com.
> g1.b.yahoo.com.         172800  IN      NS      yf5.yahoo.com.
> g1.b.yahoo.com.         172800  IN      NS      yf6.yahoo.com.
> g1.b.yahoo.com.         172800  IN      NS      yf7.yahoo.com.
> ;; Received 310 bytes from 66.218.71.63#53(ns1.yahoo.com) in 233 ms
> 
> And without "+trace" argument:
> 
> # dig @dns2.mydomain.com www.yahoo.com.ar
> 
> ; <<>> DiG 9.4.2 <<>> @dns2.mydomain.com www.yahoo.com.ar
> ; (1 server found)
> ;; global options:  printcmd
> ;; connection timed out; no servers could be reached
> 
> Why with 'trace' the query seem to finish, and without 'trace' it fails?

Yes, why? I have discussed this in another thread - "Recursive queries
fail if query source port is not fixed" - see
<http://marc.info/?l=bind-users&s=nordhaug>
I haven't followed all posts in this thread, but my problem appears
only if I have random query source port - any fixed number is OK.

Hans