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Date: Wed, 29 Jun 2011 18:10:37 +0300
From: Oleg Cherevko <olwi@fb-n.l.org.ua>
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Subject: ifconfig alias: same subnet netmask question
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Hi All,

When describing the "alias" parameter ifconfig manpage claims that "If 
the address is on the same subnet as the first network address for this 
interface, a non-conflicting netmask must be given. Usually 0xffffffff 
is most appropriate."

Taking into account that FreeBSD supports aliases from the same subnet 
with identical netmask for 6+ years now, does this statement still make 
sense? And what does this "conflicting netmask" stand for (I mean in the 
context of more or less recent FreeBSD versions, say 8.0+)?

Are there any drawbacks in setting aliases like this:
	ifconfig em0 inet 192.168.1.1 netmask 0xffffff00
	ifconfig em0 inet 192.168.1.2 netmask 0xffffff00
instead of traditional:
	ifconfig em0 inet 192.168.1.1 netmask 0xffffff00
	ifconfig em0 inet 192.168.1.2 netmask 0xffffffff
(again, for more or less recent FreeBSD versions)?

-- 
Olwi