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SubjectRE: howto disable auto route setup?
Date

> -----Original Message-----
> From: owner-linux-kernel@vger.rutgers.edu
> [mailto:owner-linux-kernel@vger.rutgers.edu]On Behalf Of
> David Woodhouse
> Sent: Tuesday, February 02, 1999 2:11 PM
> To: Martin Mares
> Cc: Mike Jagdis; Sam Mortimer; linux-kernel@vger.rutgers.edu
> Subject: Re: howto disable auto route setup?
> By flagging an interface as 'pointopoint $otherhost', you
> tell the kernel
> to add an outgoing route to $otherhost. Attaching a network route to a
> fictitious class [ABC] network, and a corresponding broadcast
> route, is
> semantical insanity.
>
> Yet this is what the kernel does. What possible justification
> can there be for
> the automatic creation of the route which I delete in the
> second line of this
> script? ...
>
> /sbin/ifconfig ippp0 158.152.16.50 pointopoint 158.152.1.222
> -arp -broadcast up
> /sbin/route del -net 158.152.0.0 netmask 255.255.0.0 dev ippp0
> /sbin/route add 158.152.1.222 ippp0
> /sbin/route add default gw 158.152.1.222

Point-to-Point interfaces are semantically different from broadcast
interfaces. By definition, a broadcast interface indicates that all hosts
that are in the same subnet, as defined by the IP address and netmask for
that interface, are locally reachable and do not need to be routed through
another device. Why a route to the network 158.152.0.0/16 is automatically
configured for a point to point interface as you indicate above I can't
answer. I don't think it should be. However, the same IP and netmask
configured on a broadcast interface should automatically add the
corresponding route.

It seems that people who have problems with the automatic creation of a
route are all using point to point interfaces, no? If that's the case,
can't the implementation be changed so that for point to point interfaces an
automatic route is not added, but for broadcast interfaces it is? That
seems to be the way most others implement it.

Fred


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