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List:       freebsd-net
Subject:    Re: Routing problems
From:       "Bruce M. Simpson" <bms () freebsd ! org>
Date:       2007-10-25 9:52:10
Message-ID: 4720674A.9090009 () FreeBSD ! org
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LiuJiusheng wrote:
> Linux takes 6.6.6.2 as gateway for route 4.4.4/24. But some Oses have the gateway \
> 2.2.2.2. (treat 4.4.4/24 as a recursive route). Is there any standard for this? 
> 
No, this is entirely implementation specific. Some implementations of IP 
forwarding resolve the next-hop recursively. Some don't. There is no de 
facto requirement for them to do so in any published standard I'm aware of.

The fact that FreeBSD doesn't is largely out of keeping the 
implementation simple - if the code were to perform recursive resolution 
of the next-hop, then safe bounds would need to be found for the 
recursion. It is cheaper to do this on a forwarding entry add of course, 
but routes can and do change.

BMS
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