North American Network Operators Group
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Re: Using x.x.x.0 and x.x.x.255 host addresses in supernets.

  • From: Joshman at joshman dot com
  • Date: Thu Jan 10 11:26:56 2008
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It's funny that you ask. The organization I am working with that spawned this question in the first place has /22 dhcp pools at multiple sites-- for both VoIP and workstations.  "For future growth..." they said.  Why the decision was made not to scale with additional VLANs at a later date is beyond me(or my pay-grade).

They thought it was preposterous that I suggested that there are a lot of providers/networks that exclude .0 and .255 host addresses from DHCP pools/etc,  and do not use them as a matter of convention/best practice.  I casually suggested this fact and was subsequently chided.

The reason I posed this question in the first place, is that in my experience, most organizations I have worked with do not use them.   It appears from the thread that there are some legitimate concerns with using .0 and .255 hosts, even though many consider these concerns dated or legacy. 

Thanks to everyone for their opinions.

Keegan Holley <[email protected]> wrote:
 
Call me old fashioned but I've never had to use a /23 to address a LAN subnet.  Do you really have a need to have all 500+ devices in the same VLAN?
Keegan

 
----- Original Message -----
From: "Joshman at joshman dot com"
To: [email protected]
Subject: Using x.x.x.0 and x.x.x.255 host addresses in supernets.
Date: Tue, 8 Jan 2008 05:45:36 -0800 (PST)

Hello all,
As a general rule, is it best practice to assign x.x.x.0 and x.x.x.255 as host addresses on /23 and larger?  I realize that technically they are valid addresses, but does anyone assign a node or server which is a member of a /22 with a x.x.x.0 and x.x.x.255?  Is it just a manner of preference on whether or not to use them, or are there functional reasons you shouldn't; either with rfc 1918 addresses or public addresses.
Thanks in advance,
J
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