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Date: Tue, 26 Oct 2010 13:04:18 -0500
From: Dan Nelson <dnelson@allantgroup.com>
To: Joe Auty <joe@netmusician.org>
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Subject: Re: IP aliasing and Postfix
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In the last episode (Oct 26), Joe Auty said:
> Hello,
> 
> I have a few IP aliases setup:
> 
> em0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
>         options=9b<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,VLAN_HWCSUM>
>         ether 00:0c:29:79:d5:66
>         inet <address1> netmask 0xffffff80 broadcast <broadcast address>
>         inet <address2> netmask 0xffffff80 broadcast <broadcast address>
>         inet <address3> netmask 0xffffff80 broadcast <broadcast address>
>         media: Ethernet autoselect (1000baseT <full-duplex>)
>         status: active

I usually set up aliases with a /32 netmask, which seems to be a hint to the
kernel that outgoing packets shouldn't use that IP.  I then put the correct
netmask on the "primary" ip.

-- 
	Dan Nelson
	dnelson@allantgroup.com