Antw: Re: netmon and /etc/hosts ?

2000-06-15 11:47:11
Subject: Antw: Re: netmon and /etc/hosts ?
From: "Michael Seibold" <Michael.Seibold AT Gek DOT de>
To: nv-l AT lists.tivoli DOT com
Date: Thu, 15 Jun 2000 17:47:11 +0200
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.)

Maybe you write a little script looking for all ip-addresses in your netview 
and then try to sort them and look if they are all in the domain your 
nameserver is responsible for and check the time he needs to answer.

Michael Seibold

>>> schafer AT tkg DOT com 15.06.2000  16.28 Uhr >>>
REIBENSCHUH Alfred wrote:

> ok, i have to correct the information about our setup:
> we have a caching-only bind running on the loopback interface
> which uses round-robbing to query our 3 company dns
> and the /etc/netsvc.conf specifies local,bind as resolv order


  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.    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

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:


(If the above appears on two lines it wrapped)

> mfG. Alfred Reibenschuh
> Networkmanagement
> A-1020 Wien, Lassallestrasse 5
> T: ++43-1-21717-58947
> F: ++43-1-21717-58979
> E: alfred.reibenschuh AT it-austria DOT com 
> -----Original Message-----
> From: lclark AT US.IBM DOT COM [mailto:lclark AT US.IBM DOT COM] 
> Sent: Thursday, June 15, 2000 3:15 AM
> To: NV-L AT tkg DOT com 
> Subject: Re: [NV-L] netmon and /etc/hosts ?
> The conventional wisdom is that when the hosts file gets too big,
> you ought to use a DNS, and to keep that responsive, you ought to
> put a secondary nameserver right on the Netview server. If the large
> hosts file contains names you don't need, you could of course prune it.
> I know some customers shove a corporate hosts file around to all
> systems nightly. Of course with a box that big, it's probably just the
> names you need!
> Cordially,
> Leslie A. Clark
> IBM Global Services - Systems Mgmt & Networking
> Detroit
> ---------------------- Forwarded by Leslie Clark/Southfield/IBM on
> 06/14/2000 09:07 PM ---------------------------
> Ray Schafer <schafer AT tkg DOT com>@tkg.com on 06/14/2000 02:01:50 PM
> Please respond to IBM NetView Discussion <nv-l AT tkg DOT com>
> Sent by:  owner-nv-l AT tkg DOT com 
> To:   IBM NetView Discussion <nv-l AT tkg DOT com>
> cc:
> Subject:  Re: [NV-L] netmon and /etc/hosts ?
> REIBENSCHUH Alfred wrote:
> > Hi !
> >
> > the machine      : ibm-rs6000 s7a 4-way 8gb memory 9gb swap 72gb disks
> > the system       : aix 4.3.2
> > the program      : tivoli/netview 6.0a
> > the configuration: no DNS, a well established /etc/hosts (6000 lines
> plus)
> >
> > on a " ovstart netmon ; netmon -M 53 " it takes hours
> > to get something other into the trace-file than
> > "event suppression installed"
> This is something to check out before you attempt to attack the problem by
> changing /etc/hosts:
> Be sure that you do not have an /etc/resolv.conf file.  If you have one,
> and
> especially if you have an entry to a nameserver in there, this could
> account
> for the delay: it will cause the systems resolver routines to query the
> nameserver before it looks in /etc/hosts.  It has to wait for an answer
> from
> the nameserver first.  AIX resolver routines will, (unless you tell it
> otherwise through /etc/netsvc.conf or the NSORDER environmental variable)
> use  DNS first IFF /etc/resolv.conf exists.
> --
> Ray Schafer                   | schafer AT tkg DOT com 
> The Kernel Group              | Distributed Systems Management
> http://www.tkg.com 
> _________________________________________________________________________
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Ray Schafer                   | schafer AT tkg DOT com 
The Kernel Group              | Distributed Systems Management

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