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    <title>About Load Balancing Using VRRP </title>
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<a name="wp1084590"> </a><h1 class="pTitle">
About Load Balancing Using VRRP

</h1>
<a name="wp1084591"> </a><p class="pBody">
You can configure Virtual Router Redundancy Protocol (VRRP) load balancing for iSLB. The host is 
configured with a VRRP address as the portal address. When the VRRP master port receives the first 
iSCSI session from an initiator, it assigns a backup port to serve that particular host. The information is 
synchronized to all switches through CFS if recovery is needed when a master port fails. The initiator 
gets a temporary redirect iSCSI login response. The host then logs in to the backup port at its physical 
IP address. All iSCSI interfaces in a VRRP group that has load balancing enabled must have the same 
interface VSAN, authentication, proxy initiator mode, and forwarding mode. 

</p>
<a name="wp1084595"> </a><p class="pBody">
You can configure Virtual Router Redundancy Protocol (VRRP) load balancing for iSLB. 

</p>
<a name="wp1084602"> </a><p class="pBody">
The host is configured with a VRRP address as the portal address. When the VRRP master port receives 
the first iSCSI session from an initiator, it assigns a backup port to serve that particular host. This 
information is synchronized to all switches through CFS if recovery is needed when a master port fails. 
The initiator gets a temporary redirect iSCSI login response. The host then logs in to the backup port at 
its physical IP address. If the backup port goes down, the host will revert to the master port. The master 
port knows through CFS that the backup port has gone down and redirects the host to another backup 
port.

</p>
<a name="wp1084603"> </a><p class="pBodyAutonumNoRule">
<strong>Note	&nbsp;&nbsp;&nbsp;</strong> If an Ethernet PortChannel is configured between the IPS module and an Ethernet switch, the load 
balancing policy on the Ethernet switch must be based on source/destination IP address only, not port 
numbers, for load balancing with VRRP to operate correctly. 

</p>
<a name="wp1084604"> </a><p class="pBodyAutonumNoRule">
<strong>Note	&nbsp;&nbsp;&nbsp;</strong> An initiator can also be redirected to the physical IP address of the master interface.

</p>
<a name="wp1084605"> </a><p class="pBodyAutonumRel">
<strong>Tip	&nbsp;&nbsp;&nbsp;</strong> iSLB VRRP load balancing is based on the number of iSLB initiators and not number of sessions. Any 
iSLB initiator that has more targets configured than the other iSLB initiators (resulting in more sessions) 
should be configured with a higher load metric. For example, you can increase the load metric of the 
iSLB initiator with more targets to 3000 from the default value of 1000.

</p>
<a name="wp1084606"> </a><p class="pCaution">
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<strong>Caution	&nbsp;&nbsp;&nbsp;</strong>
</td>
<td>
<p>A Gigabit Ethernet interface configured for iSLB can only be in one VRRP group because redirected 
sessions do not carry information about the VRRP IP address or group. This restriction allows the slave 
backup port to uniquely identify the VRRP group to which it belongs.
</p>
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</table>

</p>
<hr /><br><p class="pBody">Copyright 2010-2013, Cisco Systems, Inc. All rights reserved.</p> 

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