Re: netmon and /etc/hosts ?

2000-06-15 12:49:20
Subject: Re: netmon and /etc/hosts ?
From: Ray Schafer <schafer AT tkg DOT com>
To: nv-l AT lists.tivoli DOT com
Date: Thu, 15 Jun 2000 16:49:20 +0000

I understand.  I think Michael Seibold hit on the problem:   NetView is trying
to resolve a name to an address, it's not in the local cache, so it goes out to
your other name servers, and this is what is taking 1 minute or 2.  You can try
using ovtopodump and grep for "Node" then find all your IP names and put them
in a list, then try to resolve each one.  That should show you what names you
are having trouble with.   When you are able to quickly resolve them all,
netmon will work much better.

REIBENSCHUH Alfred wrote:

> >Alfred,
> >Assumptions:
> >
> >  1. Originally you said that you were blocked in some system calls that
> took
> >     1 to 2 mins.  I assume you were talking about the gethostbyaddr()
> calls.
> >  2. You have an 4 way  s7a with 8GB RAM.
> >  3. You have an /etc/resolv.conf file
> >Your problem cannot be with the /etc/hosts file.  There is no way an s7a
> with
> >sufficeint memory to suck up a large /etc/hosts file is going to take 1 to
> 2
> >minutes to parse it.
> during a debugging session the gethostbyname() calls take for about 1 minute
> NOT the gethostbyaddr() calls
> >You must have a problem with DNS.  Further, it
> >appears that the addresses you are trying to resolve are not in /etc/hosts
> >(since your netsvc.conf file says to use local /etc/hosts first, then DNS).
> >Also, I don't think you can run bind on the loopback address only.  Maybe
> you
> >are running named, and /etc/resolv.conf has the nameserver set to
> ok, once more
> we have a combined host/dns resolving strategy
> with resolv order hosts-file then dns
> we have a named(bind) running on the netview-host
> in caching-only mode (do you know what means?)
> the named is configured to forward any request he can't
> satisfy to the 3 company nameservers using a round-robbing
> algorithm and cache the data till TTL ends (usually 2 days)
> >I would try to do something about that /etc/hosts file, but that is really
> >not going to help much.  I think what you should do is what Leslie
> suggested:
> >make the machine a secondary name server.  Here is a useful link for you:
> >
> >http://www.rs6000.ibm.com/doc_link/en_US/a_doc_lib/aixbman/commadmn/tcp_nam
> eres.htm
> i'll read it but i don't think it will tell me anything
> new about tcp/ip or dns and name-resolution strategies
> >from: Michael Seibold
> >We once had some problems when netview tried to lookup ip-addresses
> >which were not in the /etc/hosts and not in the nameserver configured
> >in resolv.conf, so this nameserver had to ask another nameserver which
> >was not responding. As a result netmon was stuck and no status changes
> >took place (icons remained red, new icons remained blue  etc.)
> thats why we use a caching-nameserver with 3 other dns-servers behind it
> which all have the same name-database (this is throughly tested)
> -- alfred reibenschuh
> _________________________________________________________________________
> NV-L List information and Archives: http://www.tkg.com/nv-l

Ray Schafer                   | schafer AT tkg DOT com
The Kernel Group              | Distributed Systems Management

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