Nicholas,

The subnet mask identifies to a computer or router which bits in the IP address to check to identify a network number.  The IP address is 32 bits long usually expressed in dotted decimal ( i.e. 255.255.255.0) with 8 bits per octet.  The first octet ( the octet on the far left) identifies the class of the IP address. There are 3 classes of address that are routed on the Internet: 
    Class A  - The first bit of the first octet is always 0 (binary)
                    IP address range 1-126
                    default subnet mask - 255.0.0.0
        The address range 127.0.0.0 to 127.255.255.255 is reserved for the Loop back address - used for testing

    Class B - First two bits of the first octet are always 10 (binary)
                   IP address range 128-191
                   Default subnet mask 255.255.0.0

    Class C - First 3 bits of the first octet are always 110 (binary) 
                    IP address range 192-223
                    Default subnet mask 255.255.255.0

A computer or Router use the subnet mask to identify the network that the IP address belongs to.  This is done through a logical AND process where the bits of the IP address are compared with the bits of the subnet mask.  The binary system uses 1s and 0s to identify decimal numbers.  Since the subnet mask is binary it can only contain multiples of 2's (i.e. 1, 2, 4, 8, 16, 32, 64, and 128) relating to a bit in the 8 bit octet with the one relating to the right most bit of the octet.  

Decimal
Representation   128   64   32   16   8     4    2    1

Bits in
Subnet mask        1       1     1     1    1    1    1     1 

If every bit in the octet is a 1 then the decimal representation for the subnet mask is 255 (obtained from adding the decimal equivalent of each bit)  Every 1 in the octet of the subnet mask tells the computer that the bit must match ( and the bit is added to determine the subnet mask), 0s tell the computer to ignore that bit (the decimal equivalent of the bit is ignored and not added to identify a subnet mask or network number).   By comparing the bits in the subnet mask to the bits in the IP address the computer or router identifies the network that the IP address is located on.  By using 10.20.30.40 as your subnet mask, your computer was unable to identify a network number, as this is not a valid subnet mask.  

Mary Wolden
A+, Net+, MCP+I, MCSE, CNA, CCNA, CCAI

----- Original Message ----- 
From: "NICHOLAS BACETTI" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Monday, December 03, 2001 7:32 AM
Subject: Re: [PCBUILD] Network Neighborhood not displaying network computers


Just wanted to thank everyone for the great suggestions and comments.  

As Tom T. suggested, I went back and changed the subnet mask from 10.20.30.40 to 255.255.255.0, and everything is working just fine.  Network neighborhood is displaying the other computer on the network.  Also, I can now ping by name, as well as, by IP address (the latter wasn't a problem, the former was).  This was a good point brought up by Dave G.  Finally, as suggested by most, I did find the IP and subnet mask numbers, listed with the second adapter under the "PPP adapter".

If anyone would care to comment, what was wrong with the 10.20.30.40 subnet mask number.  Is this part of a standard governing networks?  Again thanks to all...Nick

>>> [log in to unmask] 11/29/01 10:14 AM >>>
You sound like you know how to set up tcp/ip, but your symptoms also sound
like an incorrect ip or mask entries.  The first 3 groups of the ip address
should be the same, and the mask should be 255.255.255.0
The workgroup under the identification tab needs to be the same on all
computers, I assume you are not using a domain or a server.
The reason winipcnf may not display your settings is the first adapter it
displays is 'PPP adapter'.  Use the drop down arrow to select your hardware
adapter.  Now your ip and mask settings should appear.  It will only release
and reset if you are obtaining an ip address automatically.
Tom Turak

-----Original Message-----
From: Nicholas Bacetti [mailto:[log in to unmask]]
Sent: Wednesday, November 28, 2001 3:26 PM

I've set up a two PC network using a hub, both machines are running Win98.
The problem I'm having is that when I launch network neighborhood, the only
icons that are displayed are the Entire Network icn, and the host
computer's icon.  If I further click on Entire Network, no additional icon
are displayed within Entire Network.  How can I get Network Neighborhood to
display an icon for the other computer on the network?

FYI, I can ping one computer from the other.  Furthermore, if I go to
Start>Find>Computer>Name, and enter the name of the other computer, it
returns a message "computer not found", however if I enter the IP address of
the other computer, it returns a linked icon to the other computer, which I
can launch, and which displays those folders and printers that I've set up
to
 share.  In fact, I can print from the remote computer.

One last piece of info, when I launch winipconf, the IP addess and subnet
mask aren't present.  However, they are present under the properies box, in
the TCP/IP<Network<Control Panel option.  (I manually entered both the IP
and subnet under  "Specify an IP address").

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