How does it work the Secondary Server?

[Mark Andrews]

	The original question was about listed nameservers for
	the zone not nameservers listed in resolv.conf.

> Ricardo, ALL,
> 
> I have the exact same problem (case b.)
> 
> I used libresolv library and here is the behavior I found.
> 
> Actually, in case b, there are again two cases.
> 1. Machine is Up but named is down.
> 2. Machine is down.
> 
> In first case,
> 1. Using UDP.
> 	Every request goes is to primary/secondary in a round robin
> fashion.
> 	Without lowest timeout of 1 sec, this is still very slow.
> 	I could not figure out how to tell the client library to stick
> to one 	that 	last succeeded.

	Actually it should get a ICMP port unreachable back which
	with a connected UDP socket will cause libresolv to move
	onto the next listed server.  Libresolv uses connected UDP
	sockets to talk to the recursive servers.

> 2. Using TCP.
> 	Much faster than UDP as it quickly gets a RESET packet for a SYN
> request.
> 	TCP_STAYOPEN did not work in this case.I was expecting to use
> the same 	connection for additional requests
> 
> Second case,
> 
> 1. Using UDP,
> 	same behavior
> 2. Using TCP
> 	The SYN packets are not responded and tcp stack takes about 5
> minutes to fail on the fist machine. SYN_ACK_RETRIES was set to 5. I got
> to down to  less than 30 seconds  by setting the parameter to 2.
> So if you are performing two queries, it takes 10 minutes to succeed. 
> 
> But when I use the "host" or "dig" application, it is really fast in all
> the above scenarios. 
> 
> Any idea what I am doing wrong?
> 
> Thanks,
> Shiva
> 
> >-----Original Message-----
> >From: bind-users-bounce at isc.org [mailto:bind-users-bounce at isc.org] On
> >Behalf Of Ricardo Martinez
> >Sent: Monday, April 02, 2007 2:13 PM
> >To: bind-users at isc.org
> >Subject: How does it work the Secondary Server?
> >
> >Hello list.
> >	I have a general question about how the seconday/slave server
> works.
> >Please correct me if i'm wrong.
> >I have two DNS bind servers, one is the primary server and the other,
> as
> >you could guess, is the secondary/slave server.   My question is
> related to
> >the way the requests are procesed in
> >
> >a.- Normal Situation
> >b.- Failure of the Primary Server
> >c.- Failure of the Secondary Server
> >
> >Can someone explain to me how this work, i'm a little bit confused
> >especially when a failure occurs.
> >For example in normal situation the request from the root servers
> arrives
> >50% to my primary server and 50% to my secondary, isn't?  If so, what's
> the
> >idea of a secondary server if primary goes down? it will keep receiving
> >requests even if the server is down?
> >
> >Hope that someone could explain to me this.
> >Thanks in advance
> >
> >Regards,
> >Ricardo.-
> >
> 
> 
-- 
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: Mark_Andrews at isc.org