From: Jay Hennigan (jay@xxxxxxxx)
Date: Fri Aug 09 2002 - 13:24:10 GMT-3
On Fri, 9 Aug 2002, Wright, Jeremy wrote:
> someone made a statement to me that using this network address is not a good
> practice. can anyone validate/prove wrong this statement?
Legacy subnet-zero issue.
The IP you've specified is a host on 10.0.0.0/24. This has a network
(all zeros) address of 10.0.0.0 and a broadcast (all ones) of 10.0.0.255.
Classful addressing schemes can't differentiate between 10.0.0.0/24 and
10.0.0.0/8 based on the network address. This can result in issues with
older hardware and/or software and as such isn't recommended. Back in
the days when I took the CCNA exam, Cisco wanted answers to subnetting
questions that avoided the use of subnets falling on all-zeros or all-ones.
I don't know if they've updated the tests to reflect subnet-zero as being
valid now.
Grep the CD for the IOS command "ip subnet-zero" for more detail. Until
recently this was disabled by default, now enabled by default.
So, for absolute compatibility with older-than-dirt gear, use of that
subnet probably isn't best practice. But, with anything made in the
last few years it is no longer an issue.
-- Jay Hennigan - CCIE #7880 - Network Administration - jay@west.net NetLojix Communications, Inc. - http://www.netlojix.com/ WestNet: Connecting you to the planet. 805 884-6323
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