Chapter 8: High Availability And Load Balancing; High Availability - Extreme Networks Sentriant AG Software User's Manual

8 High Availability and Load Balancing

High Availability

High availability occurs when one or more ESs takes over for an ES that has become unavailable in a
multiple-server installation.
Once an ES becomes unavailable, the other ESs take over enforcement from the ES that is now
unavailable. All ESs participate in enforcement. The MS provides notification in the user interface at the
top of the Home window. For example, if an ES is unavailable, the notification indicates that at the top
of the Home window.
When Sentriant AG is installed inline in a multiple-server configuration (Figure 129), the multiple ESs
form a network loop (an undesired condition). The Spanning Tree Protocol (STP) detects the loop and
closes one of the offending ports on the switch based on the switch configuration. If an ES becomes
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Sentriant AG Software Users Guide, Version 5.3