Re: Using x.x.x.0 and x.x.x.255 host addresses in supernets.

[Joshman at joshman dot com <yoshwa69 () yahoo com>]

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 <keegan_holley () email com> 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: nanog () merit edu
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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