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Date:      Sun, 14 Jul 1996 12:23:27 -0400
From:      dennis@etinc.com (dennis)
To:        "JULIAN Elischer" <julian@ref.tfs.com>
Cc:        hackers@freebsd.org
Subject:   Re: interfaces, routes, etc.
Message-ID:  <199607141623.MAA18495@etinc.com>

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>> My suggestions...
>> 
>>   - Automatically generated link layer routes get removed when an
>>     interface is brought down.

This should depend on what you mean by "down". If the link is adminstratively
brought 'down", yes, but if on a PTP the line goes flakey for a few minutes
(because the telco is playing games, like ours does sometimes on a 
saturday morning), it shouldnt affect the routes. If you're changing an address
you should delete the old addresses explicitly.

>> Another question:
>> 
>>  - Exactly what is the netmask, as configured on a point-to-point
>>    interface, used for? If anything, which address does it apply to,
>>    the local or the remote one?

This is something that should be fixed, as the routes are added at "host"
when you set up a PTP address pair, yet the netmask is set the the natural
mask of the local address, which is arguable wrong. The broadcast address
(if broadcasting is on) should also be the destinination address of the PTP, 
not the broadcast address formulated using the netmask.

>>   - Allow NMBA type addressing on point-to-point links like this:
>> 
>>       tun1: flags=8051<UP,POINTOPOINT,RUNNING,MULTICAST> mtu 1500
>> 	      inet 1.1.1.1 --> 2.2.2.2 netmask 0xff000000 
>> 	      inet 1.1.1.1 --> 3.3.3.3 netmask 0xff000000 
>> 	      inet 1.1.1.1 --> 4.4.4.4 netmask 0xff000000 

Why would you want to alias like this on a PTP? This particular example is
very wrong, because the definition of a PTP link is one entity on each side
of the link. The above should be configured:

tun1: flags=8051<UP,POINTOPOINT,RUNNING,MULTICAST> mtu 1500
>> 	      inet 1.1.1.1 --> 2.2.2.2 

route add 3.3.3.3   2.2.2.2
route add 4.4.4.4   2.2.2.2

if you have multiple gateways on a PTP link the routing software has no way
of knowing what the gateway is for a particular packet, and you'll break stuff
that depends on such things. 

gated will also choke badly on such a configuration.


Dennis

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