8.1 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 Novell ZENworks Network Access Control is installed inline in a multiple-server configuration (Figure 8-1), 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 unavailable, the switch reconnects so that there is always a path from the VPN to an ES. All of the ES firewalls continuously stay in sync with each other.

Figure 8-1 Inline Installations

Figure 8-2 DHCP Installation

Figure 8-3 802.1X Installation