Re: alias netmask bug?

Jeremy Chadwick wrote:
On Tue, Jul 24, 2007 at 03:34:54AM +0300, Evren Yurtesen wrote:
I remember from earlier versions of FreeBSD that it had a restriction about alias IP netmasks (somewhere in 3.x,4.x days)...

as explained here:
http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/configtuning-virtual-hosts.html

However I tried on the loopback interface to add a 2nd IP with the same netmask as the original IP and it accepts it fine. (on 6.2)

lo0: flags=8049<UP,LOOPBACK,RUNNING,MULTICAST> mtu 16384
inet 127.0.0.1 netmask 0xff000000
inet 127.0.0.2 netmask 0xff000000

Is FreeBSD allowing this a bug or ???

It's not a bug. Why did you disregard the instructions, though?

If this is not a bug. What happens if an interface which is connecting to the machine has 2 IP addresses with same netmask which is not 255.255.255.255? Does FreeBSD use each IP randomly?

Don't know, but my guess is no, it probably does not use "each IP
randomly", and I cannot even fathom the network breakage that would
ensue as a result of such.


I have seen systems that have been configured like this (on physical interfaces) have some strange problems. I'm sure one box that got a config like this by accident kicked one of the IP's off the interface several hours after it was set up. Never been able to reproduce that though.

Tom
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