Netgear XCM8806 Chassis User Manual - Page 69

NETGEAR 8800 User Manual Table 11. Node States (Continued) Node State MASTER STANDBY Description In the primary (master) state, the node is responsible for all switch management functions. In the standby state, leader election occurs-the primary and backup nodes are elected. The priority of the node is only significant in the standby state. Understanding Hitless Failover Support The term hitless failover has slightly different meanings on a modular chassis. On a modular chassis, MSMs/MMs do not directly control customer ports; such ports are directly controlled by separate processors. When a modular chassis MSM/MM failover occurs, all of the ports in the chassis are under the control of separate processors which can communicate with the backup MSM/MM, so all ports continue to function. As described in the section Understanding System Redundancy on page 64, if you install two MSMs/MMs (nodes) in a chassis, one assumes the role of primary and the other assumes the role of backup. The primary node provides all of the switch management functions including bringing up and programming the I/O modules, running the bridging and routing protocols, and configuring the switch. The primary node also synchronizes the backup node in case it needs to take over the management functions if the primary node fails. The configuration is one of the most important pieces of information checkpointed to the backup node. Each component of the system needs to checkpoint whatever runtime data is necessary to allow the backup node to take over as the primary node if a failover occurs, including the protocols and the hardware dependent layers. For more information about checkpointing data and relaying configuration information, see Replicating Data Between Nodes on page 66. Not all protocols support hitless failover; see Table 12 for a detailed list of protocols and their support. Layer 3 forwarding tables are maintained for pre-existing flows, but subsequent behavior depends on the routing protocols used. Static Layer 3 configurations and routes are hitless. You must configure OSPF graceful restart for OSPF routes to be maintained, and you must configure BGP graceful restart for BGP routes to be maintained. For more information about OSPF, see Chapter 24, OSPF, and for more information about BGP, see Chapter 26, BGP. For routing protocols that do not support hitless failover, the new primary node removes and re-adds the routes. Protocol Support for Hitless Failover Table 12 summarizes the protocol support for hitless failover. Unless otherwise noted, the behavior is the same for all modular switches. If a protocol indicates support for hitless failover, additional information is also available in that particular chapter. For example, for information about network login support of hitless failover, see Chapter 16, Network Login. Chapter 3. Managing the Switch | 69