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Date:      Sat, 21 Oct 2000 16:05:42 +0200
From:      Udo Erdelhoff <ue@nathan.ruhr.de>
To:        freebsd-net@freebsd.org
Subject:   mpd, the Windows VPN Client and subnets
Message-ID:  <20001021160542.A7418@nathan.ruhr.de>

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Hi,
short version of my question: Is it possible to pass a subnet mask and/or
a broadcast address to a client during the negotiation?

Longer version of the question:
I'm having lots of fun with this setup.

Company LAN      <--> FreeBSD 4.1.1, MPD  <--> Internet <--> Win98 VPN Client
172.16.188.0/22   172.16.191.212  192.168.1.1

[The IP adresses have been changed to protect the innocent. The real
setup uses routable addresses]

The Windows box can connect to the outside interface of the FreeBSD box
and establishes a pptp connection. During the negotiation, the client
requests to use an IP address from the 172.16.188.0/22 network. The
server agrees to this and everything seems to be just fine.

Except logging in to the NT domain and browsing.

The problem is the subnet mask used by the Windows box. It uses the IP
address 172.16.191.204, the address belongs to a Class B network, ergo:
Subnet mask is 255.255.0.0, broadcast address is 172.16.255.255.

By default, Windows uses broadcasts to find the domain controllers and
browse masters. The FreeBSD box uses the correct subnet mask on its internal
interface and drops all the broadcasts to 172.16.255.255. The windows box
can't locate its servers, game over.

The obvious solution is to istop using windows. Unfortunately, TPTB do not
accect this solution. I can't define the subnet mask in the DUN entry,
I can't change the default value in the network control panel because
some of these clients need several different VPN links.

I'll have to transmit the correct subnet mask and broadcast address during
the link negotiation. Is it possible to do this with mpd?

/s/Udo
-- 
"Just say NO to network abuse. No mercy, no quarter, no survivors, no regret,
no remorse."


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