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DNS hangs

Posted on 2000-05-12
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Last Modified: 2010-04-20
I run a primary for about 70 zones however of late my dns hangs for long periods I suspect the problem is with reverse lookups because when I use a debug level of 2 I see it timing out when reverse resolving my nameserver's IP.it says can't find server name for address 216.x.x.x no response from server however if I restart named it looks up just fine.
If it matters I am running suse linux 6.1 kernel 2.2.7
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Question by:ksemat
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by:jlevie
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It could be a problem with your zone files. If that's the case you can probably find out where the problem is by using nslint. It's available from ftp://ftp.ee.lbl.gov/nslint.tar.Z and if it doesn't fuss you can be pretty sure that the zone files are okay.
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by:ksemat
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I already tried that there is no problem with my zone files.I have even looked through the logs there are no error messaes when named starts
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by:ksemat
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Except that I have multiple zones pointing to the same address however this is standard since these domains pop mail from my server and I can't put MX records on aliases as well.
Unless you have another suggestion on how I could do it.
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by:jlevie
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I honestly don't know if that's a part of the problem or not. While it's legal to have multiple zones pointing at the same IP, it's not usually considered to be good practice and can be handled better by CNAME records. The zone file for a virtual domain might have recods like:

virt1.com.          IN  MX  10 mail.mydom.com.

$ORIGIN      virtual.com.

www          IN  CNAME   chaos.mydom.com.
pop          IN  CNAME   chaos.mydom.com.

I find it interesting that the failure appears to be that of named not being able to do a reverse lookup on it's own IP (if I correctly understand what you say happens). That might possibly be related to the multiple use of the same IP as you'd have to have in-addr.arpa records for those domains (all with the same IP). Using a method like the above that situation doesn't occur as there is only one A & PTR record that references the IP.
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by:ksemat
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I doubt because though I have something like
vhost.otherdomain.com IN A 193.x.x.x
I don't have corresponding in-addr.arpa records in db.193.x.x.x but i can look them up and get an address.I only have one address for my ip that is the one for my machine.I have some other things to tell you but I will send them in e-mail as I can't pos them here.
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by:ksemat
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By the way I did it that way because without an address record the owners of the domains wouldn't be able to use nslookup to check without setting the query to any.
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by:jlevie
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Hmm, nslookup works for me on CNAME'd virtual servers. Maybe it's the copy of nslookup that they are using. I've got Linux, Solaris, Irix, and NT handy and they all return similar results, like:

levie> nslookup docs.dynetics.com
Server:  merlin.dynetics.com
Address:  192.168.0.1

Name:    mystic.dynetics.com
Address:  192.168.0.3
Aliases:  docs.dynetics.com
 
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by:ksemat
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yeah that is all well since those reside in the same file but imagine separate files for say example.com and problem.com and in db.problem you have
problem.com IN CNAME example.com
problem.com IN MX 10 example.com but no A record for problem.com
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jlevie earned 50 total points
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It doesn't matter that there's not an A record for problem.com as long as there is an A record for example.com. All of the virtual domain that I create are done this way. The only zone file that has A records is the zone file for the real hardware (and those have in-addr.arpa rcords also). Each virtual domain has a zone file containing an MX record pointing back to a real mail server and CNAME records pointing back to the the real machines that host the named virtual servers. A sample of what nslookup returns in a case like that looks like:

levie> nslookup www.entrophy-free.net
Server:  merlin.dynetics.com
Address:  192.168.0.1

Name:    chimera.dynetics.com
Address:  192.168.0.6
Aliases:  www.entrophy-free.net


All that is in the zone file for entrophy-free.net (other than the SOA & nameserver definitions) is:

entrophy-free.net.    IN MX 10 merlin.dynetics.com.
www        IN CNAME   chimera.dynetics.com.
entro
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by:ksemat
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Right but then I don't think that this would cause the hanging as it is legal and anyway it was working before perfectly but I will change the files just to remove all those error messages nslint but I really don't think that is the problem.
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by:ksemat
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I haven't got any answers but I am giving you the points since you're the only one who even tried to solve the problem.I think I am going to spend the weekend on this one I may come up with something.And thanks for all your other help I guess that is the reason I have released these points.
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