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Re: Variable subnet Masks and netview

To: nv-l@lists.tivoli.com
Subject: Re: Variable subnet Masks and netview
From: "David E. Dimond" <dimond@allina.com>
Date: Tue, 18 Apr 2000 09:21:00 -0500
Well, I'm certainly no wizard at all when it comes to variable
subnet masking, but things certainly don't look right here.  

As I understand it, the 255.255.255.255 mask is ONLY valid for a 
loopback address in certain situations.  (eg Cisco EIGRP and auto-
summary-off).  In order to variably subnet into 64 hosts you would
need a mask of 255.255.255.192 I believe.  

And for point-point links I was told that you need a mask of
255.255.255.252 to separate the network, broadcast, and hi-lo
addresses.

I could, of course, be completely wrong...

Dave Dimond
Allina Health System


W.M.de.Bruin@DNB.NL wrote:
> 
> Hi everybody,
> 
> We make use of variable subnet masking on some of our IP-Address ranges.
> An example:    In subnet 10.1.0.0 we use the first 64 adresses as host 
> adresses,
> in other words with a mask of 255.255.255.255.
>           The rest of the adresses are assigned to point-point links, with a
> mask of 255.255.255.254.
> 
> What happens now is that Netview discovers host 10.1.0.4 as a network. If you
> apply the 255.255.255.254 mask to this address, it is indeed a network, but in
> reality it is a host. Even worse: Netview thinks that host 10.1.0.3 is a
> broadcast address.
> 
> How can I convince Netview to apply a 32 bit mask to the first 65 hosts, and
> another mask to the rest of the adresses in this range?
> 
> Any help appreciated.
> 
> Regards
> Wouter de Bruin
> Network Management Consultant
> 
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