Problems with EDNS0

Tue Jul 21 19:56:39 UTC 2009

Mark Andrews escreveu:
> You think there isn't a firewall.  There is something in the path
> that is blocking responses.  When you find it can you please inform
> the manufacture that there produce is broken and you would like it
> fixed.  FORMERR is part of the base DNS specification and shouldn't
> be filtered.
>   
What I don't understand is: the FORMERR response is a normal UDP packet, ok?
What could filter this packet?

>> Queries to Akamai servers doesn't work with EDNS. To resolve this 
>> problem I configure bind with directive "server <IP> { edns no; };", but 
>> isn't a good solution.
>> From my server, some queries with EDNS works and some doesn't.
>>     
>
> The Akamai do respond to EDNS queries.
> Here is what you should be seeing.  It looks like something is
> filtering out the FORMERR responses.  Almost all of the above log
> messages are for zones where FORMERR is returned.  Responses from
> EDNS aware servers are getting back.
>
> B.T.W. you should use 512 not as the buffer size 500.
>
> drugs:dnssec 13:10 {1669} % dig @n0g.akamai.net a961.g.akamai.net +bufsize=512
>
> ; <<>> DiG 9.3.6-P1 <<>> @n0g.akamai.net a961.g.akamai.net +bufsize=512
> ; (1 server found)
> ;; global options:  printcmd
> ;; Got answer:
> ;; ->>HEADER<<- opcode: QUERY, status: FORMERR, id: 52294
> ;; flags: qr rd; QUERY: 0, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 0
>
> ;; Query time: 11 msec
> ;; SERVER: 60.254.186.21#53(60.254.186.21)
> ;; WHEN: Tue Jul 21 13:10:50 2009
> ;; MSG SIZE  rcvd: 12
>
> drugs:dnssec 13:10 {1670} % 
>
> Mark
My server gets responses with EDNS from some NS in Internet, with UDP 
packet > 512 bytes,
e.g: "dig @a.dns.br br dnskey +dnssec +bufsize=2500"
So it's not firewall problem, Am I correct ?

 From my server, dig to Akamai with EDNS (+bufsize=512) doesn't get 
FORMERR message, dig return "connection timed out; no servers could be 
reached".
What could be the reason ?

Thanks for your reply.

-- 
Ats,
Breno S. Soares
Analista de Redes
SERPRO/SUPRE/REBHE
Tel: (31) 3311-6825

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