servfail response message question

[RYAN CHERVENKA]

Barry,

The Ubuntu server is delegating a sub-domain to the LB. The LB is authoritative for the domain and is responding to client requests correctly. I removed the @  IN AAAA ::1 from the db file within the primary domain and the response was sent back to the client from the ubuntu server. Leaving the ipv6 RR in the zone db file caused the servfail. I don't know why.

Thanks,
Ryan


________________________________
 From: Barry Margolin <barmar at alum.mit.edu>
To: comp-protocols-dns-bind at isc.org 
Sent: Wednesday, June 26, 2013 10:24 AM
Subject: Re: servfail response message question
 

In article <mailman.668.1372206152.20661.bind-users at lists.isc.org>,
RYAN CHERVENKA <ryan_chervenka at yahoo.com> wrote:

> I currently have a domain example.com authoritative on my Ubuntu server and 
> it is delegating gslb.example.com to my load balancer.Ý

www.example.com is a 
> CNAME for www.gslb.example.comÝ
Gslb.example.com has an NS record pointing to 
> the LB

Client sends query for www.example.com to Ubuntu DNS server. The 
> Ubuntu DNS server sends a query to the load balancer for www.gslb.example.com 
> and the LB responds to the Ubuntu DNS server with the right A record in the 
> answer section. However, the Ubuntu server responds to the client with 
> servfail.Ý

When I look at the pcap from the Ubuntu server, the LB is 
> responding to it with the correct IP but the dig response from the Ubuntu 
> server to the client shows "no servers could be reached" when I dig against 
> the Ubuntu. I also see the same message in the dns response in the pcap 
> (obviously).

Ryans-MacBook-Pro:~ ryanc$ dig @10.10.1.50 www.example.com <-me 
> querying the Ubuntu for www.example.com

; <<>> DiG 9.8.3-P1 <<>> @10.10.1.50 
> www.example.com
; (1 server found)
;; global options: +cmd
;; connection 
> timed out; no servers could be reached


Do you have any ideas as to why this 
> is happening?

Ryan Chervenka

Why is the Ubuntu server sending the query to the LB at all? To emulate 
how a caching server works, you should be sending queries WITHOUT the RD 
flag, so the Ubuntu server should return a delegation to the LB, and 
then the caching server should query the LB.

Regarding the problem as you state it, is the LB responding 
authoritatively?

-- 
Barry Margolin
Arlington, MA

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