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Date: Thu, 30 Aug 2007 21:41:26 -0700 (PDT)
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To: dstromberglists@gmail.com
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Subject: Re: ifconfig changing a routing table?
From: David Miller <davem@davemloft.net>
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From: Dan Stromberg <dstromberglists@gmail.com>
Date: Fri, 31 Aug 2007 03:55:53 +0000 (UTC)

> I'm not accustomed to ifconfig changing the routing table.  Is this 
> normal?

Every time you enable an IP address on an interface, the
kernel creates a route to that subnet which gets likewise
deleted when you remove that IP address.

This is why you can ping hosts on your local subnet even
before you add any explicit routes.

It's been like this since ancient times and it's correct.