134 lines
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HTML
134 lines
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<meta name="DC.Title" content="Scenario: Adapter failover using virtual IP and proxy ARP" />
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<meta name="abstract" content="This solution requires you to have an external load balancing machine, such as IBM eNetwork Dispatcher. Virtual IP addresses allow you to assign an address to the system rather than to a specific interface. You can define the same address to multiple servers, which allows many new options for load balancing." />
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<meta name="description" content="This solution requires you to have an external load balancing machine, such as IBM eNetwork Dispatcher. Virtual IP addresses allow you to assign an address to the system rather than to a specific interface. You can define the same address to multiple servers, which allows many new options for load balancing." />
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<title>Scenario: Adapter failover using virtual IP and proxy ARP</title>
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<body id="rzajwlbvip"><a name="rzajwlbvip"><!-- --></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">Scenario: Adapter failover using virtual IP and proxy ARP</h1>
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<div><p>This solution requires you to have an external load balancing machine,
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such as IBM<sup>®</sup> eNetwork
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Dispatcher. Virtual IP addresses allow you to assign an address to the system
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rather than to a specific interface. You can define the same address to multiple
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servers, which allows many new options for load balancing.</p>
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<div class="section" id="rzajwlbvip__situation"><a name="rzajwlbvip__situation"><!-- --></a><h4 class="sectionscenariobar">Situation</h4><p>Your
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production iSeries™ handles
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data entry from both remote and LAN clients. It has the company's critical
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application on it. As the company has grown, so has its demand on the iSeries server
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and the network. Because of the growth, it has become imperative that this iSeries server
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be available on the network without an unscheduled down time. If, for any
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reason, a network adapter becomes unavailable, other network adapters on the iSeries server
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should take over and the network clients should be unaware of any failures.</p>
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</div>
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<div class="section" id="rzajwlbvip__objective"><a name="rzajwlbvip__objective"><!-- --></a><h4 class="sectionscenariobar">Objectives</h4><p>The
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concept of availability has many different aspects of redundancy and backup
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for failing components. In this scenario, the goal is to provide network availability
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to the iSeries server
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for its clients in the event of an adapter failure.</p>
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</div>
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<div class="section" id="rzajwlbvip__details"><a name="rzajwlbvip__details"><!-- --></a><h4 class="sectionscenariobar">Details</h4><p>One
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way to handle the preceding situation is to have multiple physical connections
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to the LAN from the iSeries server. Consider the following figure.</p>
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<div class="fignone"><span class="figcap">Figure 1. Adapter failover without local clients</span><br /><img src="rzajw528.gif" alt="Adapter failover without local clients" /><br /></div>
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<p>Each physical connection has a different IP address. Then you can
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assign a virtual IP address to the system. This virtual IP address is the
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IP address by which all of its clients recognize it. All remote clients (clients
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that are not physically attached to the same LAN as the iSeries server)
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communicate with the iSeries server through an external load balancing
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server such as a network dispatcher. When the IP requests from the remote
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clients go through the network dispatcher, the network dispatcher routes the
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virtual IP addresses to one of the network adapters on the iSeries server.</p>
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<p><img src="./delta.gif" alt="Start of change" />If the LAN that the iSeries server is connected to has clients,
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these clients will not use the network dispatcher to direct their locally
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bound traffic because that will unnecessarily overload the network dispatcher.
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You can create route entries on each client that are similar to the route
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tables in the network dispatcher. However, this will be impractical if the
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LAN has a large number of local clients. This situation is described in the
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following figure.<img src="./deltaend.gif" alt="End of change" /></p>
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<div class="fignone" id="rzajwlbvip__failoverlocal"><a name="rzajwlbvip__failoverlocal"><!-- --></a><span class="figcap">Figure 2. Adapter failover with
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local clients</span><br /><img src="rzajw526.gif" alt="Adapter failover with local clients" /><br /></div>
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<p>As of OS/400<sup>®</sup> V5R2,
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local clients (clients that are attached to the same LAN as the iSeries server)
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can connect to the virtual IP address of the iSeries server through ARP. This allows
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local clients to have an adapter failover solution as well. </p>
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<p><img src="./delta.gif" alt="Start of change" />In
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each case, neither local clients nor remote clients are aware of the failover
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when it occurs. The system chooses which adapters and IP addresses are the
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preferred interface for virtual IP address (VIPA) proxy Address Resolution
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Protocol (ARP) agent selection.<img src="./deltaend.gif" alt="End of change" /></p>
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<p><img src="./delta.gif" alt="Start of change" />Starting with i5/OS™ V5R4, you
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can manually select which adapters and IP addresses are to be the preferred
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interface for VIPA proxy ARP agent selection. You can select which interface
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to use by creating a preferred interface list if an adapter failure occurs.
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A preferred interface list is an ordered list of the interface addresses that
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will take over for the failed adapters. You can use either iSeries Navigator
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or the Change TCP/IP IPv4 Interface (QTOCC4IF) application programming interface
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(API) to configure a preferred interface list. The preferred interface list
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is also configurable for both virtual Ethernet and virtual IP address interfaces.<img src="./deltaend.gif" alt="End of change" /></p>
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<p><img src="./delta.gif" alt="Start of change" />Using <a href="#rzajwlbvip__failoverlocal">Figure 2</a> as
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an example, remote clients are communicating with the local system using virtual
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IP address 10.1.1.7. Suppose 10.1.1.4 is the initial local adapter being used
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for this communication, and you want 10.1.1.5 to take over if 10.1.1.4 fails.
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You also want interface 10.1.1.6 to take over if both adapters for 10.1.1.4
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and 10.1.1.5 have failed. To control the order in which these interfaces are
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used in a failover situation, you can define a preferred interface list for
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virtual IP address 10.1.1.7. In this case, it is an ordered list of interface
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addresses that consists of 10.1.1.4, 10.1.1.5, and 10.1.1.6.<img src="./deltaend.gif" alt="End of change" /></p>
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<p>The solution
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can also involve using two or more iSeries servers to support each other.
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If one of the iSeries systems
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become unavailable, then the second system can serve as a failover. The following
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figure shows the same setup using two iSeries servers.</p>
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<div class="fignone"><span class="figcap">Figure 3. Adapter
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failover with multiple iSeries and local clients</span><br /><img src="rzajw527.gif" alt="Adapter failover with multiple iSeries and local clients" /><br /></div>
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<p>The packet routing is the same as routing for a single iSeries server
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and its remote clients; however, there is a distinct difference for the local
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clients. If you have multiple iSeries servers using the same virtual
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IP address, you can only proxy for one of the iSeries servers. In this case, you will
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have the iSeries server
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with the two LAN connections serve as the proxy.</p>
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</div>
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<div class="section" id="rzajwlbvip__steps"><a name="rzajwlbvip__steps"><!-- --></a><h4 class="sectionscenariobar">Configuration
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steps</h4><p><img src="./delta.gif" alt="Start of change" />The configuration for load balancing using virtual
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IP and proxy ARP is very similar to standard TCP/IP configurations with the
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addition of a virtual TCP/IP interface.<img src="./deltaend.gif" alt="End of change" /></p>
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</div>
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</div>
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<div>
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<ol>
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<li class="olchildlink"><a href="rzajwconfiglb.htm">Configure load balancing using virtual IP and proxy ARP</a><br />
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Use these configuration steps for load balancing using virtual IP and proxy ARP.</li>
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<li class="olchildlink"><a href="rzajwcpil.htm">Create a preferred interface list</a><br />
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You can create a preferred interface list to control the order in which the local interfaces are used when an adapter failure occurs.</li>
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</ol>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="rzajwloadbasics.htm" title="Workload balancing is redistributing network traffic and workload of heavily accessed machines across multiple processors, multiple interface adapters, or multiple host servers.">TCP/IP workload balancing 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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