79 lines
5.4 KiB
HTML
79 lines
5.4 KiB
HTML
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<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE html
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PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html lang="en-us" xml:lang="en-us">
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
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<meta name="security" content="public" />
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<meta name="Robots" content="index,follow" />
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<meta http-equiv="PICS-Label" content='(PICS-1.1 "http://www.icra.org/ratingsv02.html" l gen true r (cz 1 lz 1 nz 1 oz 1 vz 1) "http://www.rsac.org/ratingsv01.html" l gen true r (n 0 s 0 v 0 l 0) "http://www.classify.org/safesurf/" l gen true r (SS~~000 1))' />
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<meta name="DC.Type" content="concept" />
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<meta name="DC.Title" content="Routing with virtual IP" />
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<meta name="abstract" content="Virtual IP, also called a circuitless or loopback interface, is a powerful function that can be used in many ways." />
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<meta name="description" content="Virtual IP, also called a circuitless or loopback interface, is a powerful function that can be used in many ways." />
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<meta name="DC.Relation" scheme="URI" content="rzajwrcb.htm" />
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<meta name="copyright" content="(C) Copyright IBM Corporation 1998, 2006" />
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<meta name="DC.Rights.Owner" content="(C) Copyright IBM Corporation 1998, 2006" />
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<meta name="DC.Format" content="XHTML" />
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<meta name="DC.Identifier" content="rzajwviproute" />
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<meta name="DC.Language" content="en-us" />
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<!-- All rights reserved. Licensed Materials Property of IBM -->
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<!-- US Government Users Restricted Rights -->
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<!-- Use, duplication or disclosure restricted by -->
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<!-- GSA ADP Schedule Contract with IBM Corp. -->
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<link rel="stylesheet" type="text/css" href="./ibmdita.css" />
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<link rel="stylesheet" type="text/css" href="./ic.css" />
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<title>Routing with virtual IP</title>
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</head>
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<body id="rzajwviproute"><a name="rzajwviproute"><!-- --></a>
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<!-- Java sync-link --><script language="Javascript" src="../rzahg/synch.js" type="text/javascript"></script>
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<h1 class="topictitle1">Routing with virtual IP</h1>
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<div><p>Virtual IP, also called a circuitless or loopback interface, is
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a powerful function that can be used in many ways.</p>
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<p>Virtual IP provides a way to assign one or more addresses to the system
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without the need of binding the address to a physical interface. You can use
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this function when you want to run multiple occurrences of a server bound
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to different addresses, or if you want to run other services that need to
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bind to default ports.</p>
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<p>Most environments where you might want to use virtual IP are cases where
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you want to provide multiple paths between the local gateway and the iSeries™ server,
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for example, load balancing and fault tolerance. In this context, each "path"
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implies an additional interface, and consequently, an additional, nonvirtual
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IP address on the iSeries server. The existence of these multiple interfaces
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should only be visible on the local network. You do not want the remote clients
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to have to be aware of the multiple IP addresses for the iSeries server.
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Ideally, you will like them to view your iSeries server as a single IP address.
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How the inbound packet gets routed through the gateway, over the local network,
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and to the iSeries server
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should be invisible to a remote client. The way to accomplish this is by using
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virtual IP. Local clients should communicate with the iSeries server by any of the physical
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IP addresses while remote clients see only the virtual IP interface.</p>
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<br /><img src="rzajw510.gif" alt="Routing with virtual IP" /><br /><p>The virtual IP environment is for the iSeries server that acts as the server
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for remotely connected clients. More importantly, the virtual IP address is
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on a different subnet than the physical interfaces. Moreover, the virtual
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IP address makes your iSeries server appear as a single host, not necessarily
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as one attached to a larger network or subnetwork. Therefore, the subnet mask
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for the virtual IP interface should usually be set to 255.255.255.255.</p>
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<p><img src="./delta.gif" alt="Start of change" />Because the virtual IP address is not bound to a single physical
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interface, the iSeries server
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never responds to an Address Resolution Protocol (ARP) request to the virtual
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IP address unless you enable proxy ARP for the virtual IP address. In other
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words, by enabling proxy ARP, a local interface can respond to the ARP requests
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on behalf of the virtual IP address. Otherwise, remote systems must have a
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route defined to reach the address. <img src="./deltaend.gif" alt="End of change" /></p>
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<p><img src="./delta.gif" alt="Start of change" />In the preceding example, the workstations all point to one
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of the 10.3.2 interfaces, on the iSeries server, as their next hop gateway.
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When a packet arrives at the iSeries server, it goes through the packet processing.
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If the destination address matches any address defined on the system (including
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virtual IP addresses), the system processes the packet.<img src="./deltaend.gif" alt="End of change" /></p>
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<p>The DNS servers use the addresses of the requested server. In this case,
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all the addresses represent the same system. The virtual IP function can be
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used when consolidating multiple systems into one larger system.</p>
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</div>
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<div>
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<div class="familylinks">
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<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>
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</div>
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</div>
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</body>
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</html>
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