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From: David Schwartz on 11 Jan 2010 14:20
On Jan 10, 6:17 pm, karthikbalaguru <karthikbalagur...(a)gmail.com>
wrote:

> I understand that the reasons for 16382 and
> 8190 is that the first(all zeros) and the last
> addresses(all ones) have been reserved in
> every subnet due to historical reasons.
> Can you lemme know the historical reason ?

At one time, there was a network attack called 'smurf' that involved
sending spoofed ICMP pings to broadcast addresses. The idea was that
every host on the intermediary network would send a reply packet to
your spoofed source, allowing you to use other people's networks as
attack amplifiers. As an emergency measure to stop the attack some
sites blocked all traffic to IP addresses that end in .0 or .255. If
you use those IP addresses, even though they are perfectly valid in
nets larger than /24s, you may have reachability problems.

DS
From: Tecknode on 11 Jan 2010 17:56
karthikbalaguru wrote:
> Hi,
> In Class B Subnetting,
> 1. Consider that the subnet mask is 255.255.192.0
> then, the number of hosts is 16382. The number of
> subnets is 2.
> 2. Similarly for the subnet mask of 255.255.224.0,
> the number of hosts is 8190. The number of
> subnets is 6.
>
> I understand that the reasons for 16382 and
> 8190 is that the first(all zeros) and the last
> addresses(all ones) have been reserved in
> every subnet due to historical reasons.
> Can you lemme know the historical reason ?
> I searched the internet, but did not find info
> except for some links mentioning the term
> 'historical reasons'.
>
> Further, shouldn't the number of subnets be
> 4 for the first scenario and 8 for the second
> scenario ? Any specific reasons for not using
> subnet-zero(all-zeros subnet) and
> all-ones-subnet ?
>
> Thx in advans,
> Karthik Balaguru

Did you see the following article, the "Subnet zero and the all-ones
subnet" section?

http://en.wikipedia.org/wiki/Subnetwork
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