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Date:      Sat, 31 Aug 2002 22:56:32 -0400
From:      "BSD" <bsdquestions@connect1.ca>
To:        "'Matthew Emmerton'" <matt@gsicomp.on.ca>, "'Jorge Mario G.'" <murcielako@yahoo.com>, <freebsd-questions@FreeBSD.ORG>
Subject:   RE: Problems with IP aliasing
Message-ID:  <000601c25163$2d5c6fc0$0701a8c0@silver>
In-Reply-To: <001501c24fd1$be6e1600$1200a8c0@gsicomp.on.ca>

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The only time an Alias IP can have a subnet other then a 32 bit mask
subnet is when it is the first IP of that new subnet.

In your example, you have 192.168.0.2 and you created an alias
192.168.10.1 with a 24 bit subnet mask. That is allowed because it is
different subnet then 192.168.0.1.  When you try to create the second IP
on the same subnet you got the error creating it until you give it the
subnet mask of all 255.



-----Original Message-----
From: owner-freebsd-questions@FreeBSD.ORG
[mailto:owner-freebsd-questions@FreeBSD.ORG] On Behalf Of Matthew
Emmerton
Sent: Thursday, August 29, 2002 11:03 PM
To: Jorge Mario G.; freebsd-questions@FreeBSD.ORG
Subject: Re: Problems with IP aliasing



> HI
> I'm trying to create IP aliases of the ip 192.168.0.2
> so i create the alias 192.168.10.1 with no problems
> this way:
>
> ifconfig xl0 inet 192.168.10.1 netmask 255.255.255.0
> alias
> [root@gator:/usr]# ifconfig
> xl0:
> flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu
> 1500
>         inet 192.168.0.2 netmask 0xffffff00 broadcast
> 192.168.0.255
>         inet 192.168.10.1 netmask 0xffffff00 broadcast
> 192.168.10.255
>         ether 00:10:5a:07:da:30
>         media: Ethernet autoselect (100baseTX
> <full-duplex>)
>         status: active
>
>
> [root@gator:/usr/ports/mail/squirrelmail]# ping
> 192.168.10.1
> PING 192.168.10.1 (192.168.10.1): 56 data bytes
> 64 bytes from 192.168.10.1: icmp_seq=0 ttl=64
> time=0.080 ms
> 64 bytes from 192.168.10.1: icmp_seq=1 ttl=64
> time=0.044 ms
> the alias is there and working
>
> then i tried:
> [root@gator:~]# ifconfig xl0 inet 192.168.10.2 netmask
> 255.255.255.0 alias
> ifconfig: ioctl (SIOCAIFADDR): File exists
> [root@gator:~]#
>
> any ideas why???
> thank

ifconfig xl0 inet 192.168.10.2 netmask 255.255.255.255 alias

Aliases must be created with a 255.255.255.255 (0xffffffff) netmask.
See
'man ifconfig' for details.

--
Matt Emmerton


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