Date: Mon, 6 May 2002 13:45:28 +0100 From: Ceri Davies <setantae@submonkey.net> To: doc@FreeBSD.org Subject: Advanced Networking Question Message-ID: <20020506124528.GA7841@submonkey.net>
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Hi all,
From the Advanced Networking chapter of the Handbook :
<title>Dual Homed Hosts</title>
<indexterm><primary>dual homed hosts</primary></indexterm>
<para>There is one other type of configuration that we should cover, and
that is a host that sits on two different networks. Technically, any
machine functioning as a gateway (in the example above, using a PPP
connection) counts as a dual-homed host. But the term is really only
used to refer to a machine that sits on two local-area
networks.</para>
<para>In one case, the machine has two Ethernet cards, each having an
address on the separate subnets. Alternately, the machine may only
have one Ethernet card, and be using &man.ifconfig.8; aliasing. The former is
used if two physically separate Ethernet networks are in use, the
latter if there is one physical network segment, but two logically
separate subnets.</para>
<para>Either way, routing tables are set up so that each subnet knows
that this machine is the defined gateway (inbound route) to the other
subnet. This configuration, with the machine acting as a Bridge <=====
between the two subnets, is often used when we need to implement
packet filtering or firewall security in either or both
directions.</para>
Now I could be wrong, but I was under the impression that routing was a layer
3 function, and bridging was layer two, so isn't the statement that the machine
is acting as a bridge incorrect (since it also states that the machine is doing
routing) ?
Thanks,
Ceri
--
get the cool shoe shine
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