Subnetting question?

Yes there are 510 usable hosts in a /23. Classes are really meaningless once
you break the /8, /16 or /24 boundry. Example 10.0.0.0/23 is technically a
class "A" address, it still contains 510 hosts. 172.16.0.0/23 is technically
a class "B" address, it still contains 510 hosts. 192.168.0.0/23 is
technically a class "C" address, it still contains 510 hosts.

When using a /23 mask there is a very quick shortcut you can use. If the 3rd
octet is an even number it immeadiately tells you it contains the network
address and the rest are valid hosts. If the 3rd octet is an odd number it
immeadiately tells you it contains all hosts and the broadcast address.
113.10.4.0 is a network address
186.54.3.0 is a valid host, it belongs to the 186.54.2.0/23 network.
175.33.3.255 is the broadcast address for the 175.33.2.0/23 network
26.35.2.255 is a valid host on the 26.35.2.0/23 network
152.135.7.0 is a network address
17.35.36.0 is a valid host on the 17.35.35.0/23 network

Thanks alot for the explanation-will definitely remember the /23
shortcut you explained-I think what threw me was looking at the
26.35.2.255 I thought it was a b/c because of the .255 -however I am
assuming the b/c would be 26.35.255.255 ?

On Sat, 28 Apr 2007 07:12:06 -0400


This sort of stuff gives me brain-ache :-(
Isn't it:
152.135.7.0 is the valid address and 17.35.36.0 the network address??
 

Yep, i was banging my head as well.  I concur with your selection.

You guys are absolutely correct! Not enough coffee!

We've added new IP addressing tutorial links to our webpage.  I
suggest the 3Com IP Addressing Document.  It has a workbook at the
end...quite useful.

http://ccna-exam-pass.blogspot.com/search/label/ip%20address

try this. it's good practice on subnetting

http://www.gt-solutions.com/cgi-bin/subnet-1.cgi
http://www.gt-solutions.com/cgi-bin/subnet-2.cgi

and also subnetmask calculator and explaination

http://subnetmask.info /