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Date:      Sat, 20 Mar 1999 07:46:20 +0100 (MET)
From:      Luigi Rizzo <luigi@labinfo.iet.unipi.it>
To:        dennis@etinc.com (Dennis)
Cc:        net@FreeBSD.ORG
Subject:   Re: Bridge HOW-TO?
Message-ID:  <199903200646.HAA01628@labinfo.iet.unipi.it>
In-Reply-To: <199903200027.TAA07066@etinc.com> from "Dennis" at Mar 19, 99 07:23:41 pm

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> I've been poking around some docs and havent found a definitive step-by-step
> how-to on how to make a simple bridge with freebsd. 

there is a manpage (at least in 3.1) bridge(4) and almost nothing to
configure (it's a learning bridge!). The source (sys/net/bridge.[ch])
is heavily commented so it should be reasonably clear what it does.

All the rest is the same as an ordinary freebsd machine.

> Can the box be accesses via telnet? The goal is to connect multiple ethernet

sure -- assuming one of the interface has an IP address (you don't need
it for a bridge).

> with only a few IP addresses (and where subnetting would be inappropriate)...
> but to still use the FreeBSD box as a wan router. Basically a high speed
> wan link to multiple fast ethernets.

you can do this remembering the following:

 + bridging only works between ethernet interfaces (10/100 it makes no
   difference);
 + you only need to set the IP on one of the ethernets when using
   bridging;
 + if net.inet.ip.forwarding is set to 1, the machine will still do
   routing between interfaces (including non-ethernets);
 + if you set the IP on more than one ethernet, the machine will do both
   bridging and routing between them 

So basically if your wan interface is not an ethernet you are just
fine: set one IP on the WAN if, one IP on one of the ethernets, enable
bridging and forwarding, and you are set. (and you can obviously telnet
to the bridge machine).

If your WAN interface is an ethernet, the above might still work but
with some leaks (e.g. arp will go through...) which might/might not
cause trouble.

In my private source (and in the picobsd image on my web page
http://www.iet.unipi.it/~luigi/ip_dummynet/) i do have a mechanism to
define clusters of interfaces so that each cluster acts as a standalone
bridge, and you can still do routing through interfaces.

These might go into the source tree at some point when i have the time
to test them on 4.x/3.x .

	cheers
	luigi
-----------------------------------+-------------------------------------
  Luigi RIZZO                      .
  EMAIL: luigi@iet.unipi.it        . Dip. di Ing. dell'Informazione
  HTTP://www.iet.unipi.it/~luigi/  . Universita` di Pisa
  TEL/FAX: +39-050-568.533/522     . via Diotisalvi 2, 56126 PISA (Italy)
-----------------------------------+-------------------------------------


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