|
|
|
@ -34,46 +34,50 @@
|
|
|
|
</legalnotice>
|
|
|
|
</legalnotice>
|
|
|
|
</articleinfo>
|
|
|
|
</articleinfo>
|
|
|
|
|
|
|
|
|
|
|
|
<para>Proxy ARP (RFC 1027) is a way to make a machine physically located on
|
|
|
|
<section>
|
|
|
|
one network appear to be logically part of a different physical network
|
|
|
|
<title>Overview</title>
|
|
|
|
connected to the same router/firewall. Typically it allows us to hide a
|
|
|
|
|
|
|
|
machine with a public IP address on a private network behind a router, and
|
|
|
|
|
|
|
|
still have the machine appear to be on the public network "in front of" the
|
|
|
|
|
|
|
|
router. The router "proxys" ARP requests and all network traffic to and from
|
|
|
|
|
|
|
|
the hidden machine to make this fiction possible.</para>
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
<para>Consider a router with two interface cards, one connected to a public
|
|
|
|
<para>Proxy ARP (RFC 1027) is a way to make a machine physically located
|
|
|
|
network PUBNET and one connected to a private network PRIVNET. We want to
|
|
|
|
on one network appear to be logically part of a different physical network
|
|
|
|
hide a server machine on the PRIVNET network but have it accessible from the
|
|
|
|
connected to the same router/firewall. Typically it allows us to hide a
|
|
|
|
PUBNET network. The IP address of the server machine lies in the PUBNET
|
|
|
|
machine with a public IP address on a private network behind a router, and
|
|
|
|
network, even though we are placing the machine on the PRIVNET network
|
|
|
|
still have the machine appear to be on the public network "in front of"
|
|
|
|
behind the router.</para>
|
|
|
|
the router. The router "proxys" ARP requests and all network traffic to
|
|
|
|
|
|
|
|
and from the hidden machine to make this fiction possible.</para>
|
|
|
|
|
|
|
|
|
|
|
|
<para>By enabling proxy ARP on the router, any machine on the PUBNET network
|
|
|
|
<para>Consider a router with two interface cards, one connected to a
|
|
|
|
that issues an ARP "who has" request for the server's MAC address will get a
|
|
|
|
public network PUBNET and one connected to a private network PRIVNET. We
|
|
|
|
proxy ARP reply from the router containing the router's MAC address. This
|
|
|
|
want to hide a server machine on the PRIVNET network but have it
|
|
|
|
tells machines on the PUBNET network that they should be sending packets
|
|
|
|
accessible from the PUBNET network. The IP address of the server machine
|
|
|
|
destined for the server via the router. The router forwards the packets from
|
|
|
|
lies in the PUBNET network, even though we are placing the machine on the
|
|
|
|
the machines on the PUBNET network to the server on the PRIVNET
|
|
|
|
PRIVNET network behind the router.</para>
|
|
|
|
network.</para>
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
<para>Similarly, when the server on the PRIVNET network issues a "who has"
|
|
|
|
<para>By enabling proxy ARP on the router, any machine on the PUBNET
|
|
|
|
request for any machines on the PUBNET network, the router provides its own
|
|
|
|
network that issues an ARP "who has" request for the server's MAC address
|
|
|
|
MAC address via proxy ARP. This tells the server to send packets for
|
|
|
|
will get a proxy ARP reply from the router containing the router's MAC
|
|
|
|
machines on the PUBNET network via the router. The router forwards the
|
|
|
|
address. This tells machines on the PUBNET network that they should be
|
|
|
|
packets from the server on the PRIVNET network to the machines on the PUBNET
|
|
|
|
sending packets destined for the server via the router. The router
|
|
|
|
network.</para>
|
|
|
|
forwards the packets from the machines on the PUBNET network to the server
|
|
|
|
|
|
|
|
on the PRIVNET network.</para>
|
|
|
|
|
|
|
|
|
|
|
|
<para>The proxy ARP provided by the router allows the server on the
|
|
|
|
<para>Similarly, when the server on the PRIVNET network issues a "who has"
|
|
|
|
PRIVNETnetwork to appear to be on the PUBNET network. It lets the router
|
|
|
|
request for any machines on the PUBNET network, the router provides its
|
|
|
|
pass ARP requests and other network packets in both directions between the
|
|
|
|
own MAC address via proxy ARP. This tells the server to send packets for
|
|
|
|
server machine and the PUBNET network, making the server machine appear to
|
|
|
|
machines on the PUBNET network via the router. The router forwards the
|
|
|
|
be connected to the PUBNET network even though it is on the PRIVNET network
|
|
|
|
packets from the server on the PRIVNET network to the machines on the
|
|
|
|
hidden behind the router.</para>
|
|
|
|
PUBNET network.</para>
|
|
|
|
|
|
|
|
|
|
|
|
<para>Before you try to use this technique, I strongly recommend that you
|
|
|
|
<para>The proxy ARP provided by the router allows the server on the
|
|
|
|
read the <ulink url="shorewall_setup_guide.htm">Shorewall Setup
|
|
|
|
PRIVNETnetwork to appear to be on the PUBNET network. It lets the router
|
|
|
|
Guide</ulink>.</para>
|
|
|
|
pass ARP requests and other network packets in both directions between the
|
|
|
|
|
|
|
|
server machine and the PUBNET network, making the server machine appear to
|
|
|
|
|
|
|
|
be connected to the PUBNET network even though it is on the PRIVNET
|
|
|
|
|
|
|
|
network hidden behind the router.</para>
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
<para>Before you try to use this technique, I strongly recommend that you
|
|
|
|
|
|
|
|
read the <ulink url="shorewall_setup_guide.htm">Shorewall Setup
|
|
|
|
|
|
|
|
Guide</ulink>.</para>
|
|
|
|
|
|
|
|
</section>
|
|
|
|
|
|
|
|
|
|
|
|
<section id="Example">
|
|
|
|
<section id="Example">
|
|
|
|
<title>Example</title>
|
|
|
|
<title>Example</title>
|
|
|
|
|
Tom Eastep