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<h1 class="topictitle1">Routing with point-to-point</h1>
<div><p>You can get your data from your local system to a remote system
or from a local network to a remote network with point-to-point connections.
This explains two concepts used in configuring IP addresses for a point-to-point
connection.</p>
<p>Point-to-point connections are typically used to connect two systems together
over a wide area network (WAN). You can use a point-to-point connection to
get data from your local system to a remote system or to get data from a local
network to a remote network. Do not confuse point-to-point connections with
Point-to-Point Protocol. Point-to-Point Protocol (PPP) is one type of a point-to-point
connection that is commonly used to connect a computer to the Internet. See
PPP connections for more information about how to set up and manage your PPP
connections.</p>
<p>You can use point-to-point connections across dial-up lines, leased lines,
and other types of networks such as frame relay. There are two ways that you
can configure the IP addresses for a point-to-point connection: a numbered
connection or an unnumbered connection. As the names imply, a numbered connection
has a unique IP address defined for each interface. An unnumbered connection
does not use additional IP addresses for a connection.</p>
<div class="section"><h4 class="sectiontitle">Numbered network connections</h4><p>On the surface, it
seems that the simplest way to configure a point-to-point connection is by
using a numbered connection. A numbered connection is a point-to-point definition
that has a unique IP address defined for each end of a connection.</p>
<p>Here
are some points to keep in mind when you consider a numbered point-to-point
connection:</p>
<ul><li>Each end of the connection has a unique IP address.</li>
<li>Routing statements must be added to your system to flow the traffic to
the remote system.</li>
<li>Addresses on the point-to-point link must be managed by your network administrator.</li>
<li>Addresses are used up just to connect two systems.</li>
</ul>
<p>When each point-to-point connection is defined to your iSeries™ server,
a routing entry must be made on each end to describe how to get to any network
at the other end of the connection. The routing selection process on your iSeries server
depends on having an IP address for each interface. These addresses and routes
must be managed by your network administrator. In a small network, these addresses
are easy to keep track of and do not use many additional addresses. In a large
network, however, it might take an entire subnet of addresses just to define
an interface at each end.</p>
<p>The following figure shows a numbered network
connection between two iSeries servers. A routing entry is not needed if
all you want to do is communicate from AS1 to AS2. If you want to communicate
with systems in the remote network (10.1.2.x), the routing entry included
in the figure must be added to each system. This is because the remote network,10.1.2.x,
is a part of the 192.168.1.x connection.</p>
<br /><img src="rzajw521.gif" alt="Numbered network connection" /><br /></div>
<div class="section"><h4 class="sectiontitle">Unnumbered network connections</h4><p>An unnumbered connection
is a more complex method of defining a point-to-point connection than a numbered
connection. However, you might find the unnumbered connection a simpler and
better way to manage your network.</p>
<p>The routing selection process in
the iSeries server
depends on having an IP address for an interface. In an unnumbered connection,
the point-to-point interface does not have a unique address. The IP address
of your iSeries server
interface for an unnumbered connection is actually the IP address of the remote
system.</p>
<p>Points to keep in mind while considering an unnumbered connection:</p>
<ul><li>The point-to-point interface has an address that appears to be in the
remote network.</li>
<li>Routing statements are not needed in the system.</li>
<li>Your network administration is simplified by not using up IP addresses
for the link.</li>
</ul>
<p>In the following example, AS1 appears to have an interface in the
10.1.4.x network and AS2 appears to have an interface in the 10.1.3.x network.
The AS1 is connected to LAN network 10.1.3.x with an address of 10.1.3.1.
This allows AS1 to communicate with any system on the 10.1.3.x network directly.</p>
<br /><img src="rzajw502.gif" alt="Unnumbered network connection" /><br /><p>Also shown in the example is AS2. AS2 is connected to LAN network
10.1.4.x with an address of 10.1.4.1. This allows AS2 to communicate with
any system on the 10.1.4.x network directly. Each system (AS1 and AS2) adds
the remote address to its routing table as a local interface. The address
is treated specially so that packets destined for that address will not be
processed locally. The packets for the remote address will be placed on the
interface and transported to the other end of the connection. When the packet
arrives at the other end of the connection, normal packet processing is used.</p>
<p>Now
you have a need to connect AS1 to the 10.1.4.x network and to connect AS2
to the 10.1.3.x network. If these two systems were in the same room, you can
simply add a LAN adapter to each system and plug the new interface into the
correct LAN. If you did this, AS1 and AS2 would not need any routing entries
added. In this example, however, the systems are in different cities so you
must use a point-to-point connection. Even though you are using a point-to-point
connection, you might still want to avoid adding routing entries. By defining
the Point-to-Point Protocol (PPP) connection as an unnumbered connection,
you achieve the same results that you can get if you use LAN adapters without
adding any routing entries to your iSeries server. To do this, each system
borrows the IP address of the remote system for use with route resolution.</p>
</div>
<div class="section"><h4 class="sectiontitle">Unnumbered versus numbered connection data flow</h4><p>The
following figure shows the addresses that will be used in a numbered and unnumbered
point-to-point connection. The top half of the picture shows, that with a
numbered connection, the remote system address of 192.168.1.2 or 10.1.2.1
could be used to reach the remote system. This is because there is a routing
entry in AS3 that directs packets for 10.1.2.1 to 192.168.1.2 as the next
hop. The addresses used in the return packet are based on the received packet.
The bottom of the figure shows the addresses used with an unnumbered connection.
The outbound packet has a source of 10.1.3.1 and a destination of 10.1.4.1.
No routing entries are needed on either system because the systems have a
direct interface to the remote network by using the remote system address
of the point-to-point connection.</p>
<br /><img src="rzajw503.gif" alt="Unnumbered vs. numbered" /><br /></div>
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<div class="familylinks">
<div class="parentlink"><strong>Parent topic:</strong> <a href="rzajwrcb.htm" title="Routing deals with what path the network traffic follows from its source to its destination and how that path is connected.">Routing connectivity methods</a></div>
</div>
<div class="relconcepts"><strong>Related concepts</strong><br />
<div><a href="../rzaiy/rzaiygetstart.htm">PPP connections</a></div>
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