200 lines
3.6 KiB
HTML
200 lines
3.6 KiB
HTML
<HTML
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>Building bridges, and pseudo-bridges with Proxy ARP</TITLE
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NAME="LARTC.BRIDGING"
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>Chapter 16. Building bridges, and pseudo-bridges with Proxy ARP</H1
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><DIV
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CLASS="TOC"
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><DL
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><DT
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><B
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>Table of Contents</B
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></DT
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><DT
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>16.1. <A
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HREF="lartc.bridging.iptables.html"
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>State of bridging and iptables</A
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></DT
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><DT
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>16.2. <A
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HREF="lartc.bridging.shaping.html"
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>Bridging and shaping</A
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></DT
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><DT
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>16.3. <A
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HREF="lartc.bridging.proxy-arp.html"
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>Pseudo-bridges with Proxy-ARP</A
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></DT
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><DD
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><DL
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><DT
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>16.3.1. <A
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HREF="lartc.bridging.proxy-arp.html#AEN2041"
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>ARP & Proxy-ARP</A
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></DT
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><DT
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>16.3.2. <A
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HREF="lartc.bridging.proxy-arp.html#AEN2048"
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>Implementing it</A
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></DT
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><P
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>Bridges are devices which can be installed in a network without any
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reconfiguration. A network switch is basically a many-port bridge. A bridge
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is often a 2-port switch. Linux does however support multiple interfaces in
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a bridge, making it a true switch.</P
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><P
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>Bridges are often deployed when confronted with a broken network that needs
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to be fixed without any alterations. Because the bridge is a layer-2 device,
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one layer below IP, routers and servers are not aware of its existence.
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This means that you can transparently block or modify certain packets, or do
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shaping.</P
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><P
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>Another good thing is that a bridge can often be replaced by a cross cable
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or a hub, should it break down.</P
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><P
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>The bad news is that a bridge can cause great confusion unless it is very
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well documented. It does not appear in traceroutes, but somehow packets
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disappear or get changed from point A to point B ('this network is
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HAUNTED!'). You should also wonder if an organization that 'does not want to
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change anything' is doing the right thing.</P
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><P
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>The Linux 2.4/2.5 bridge is documented on
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<A
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HREF=" http://bridge.sourceforge.net/"
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TARGET="_top"
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>this page</A
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>.</P
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>Rate limiting a single host or netmask</TD
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WIDTH="34%"
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> </TD
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>State of bridging and iptables</TD
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