Understanding Hitless Failover Support-Modular Switches Only; Protocol Support For Hitless Failover - Extreme Networks ExtremeWare XOS Guide Manual

Managing the Switch
Table 10: Node states (Continued)
Node State
FAIL
INIT
MASTER
STANDBY
Understanding Hitless Failover Support—Modular
Switches Only
As described in the section,
Switches Only" on page
(primary) and the other assumes the role of backup. The master MSM 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 master MSM also synchronizes the backup MSM
in case it needs to take over the management functions if the master MSM fails.
The configuration is one of the most important pieces of information checkpointed to the backup MSM.
Each component of the system needs to checkpoint whatever runtime data is necessary to allow the
backup MSM to take over as the master MSM if a failover occurs, including the protocols and the
hardware dependent layers. For more information about checkpointing data and relaying configuration
information, see
Not all protocols support hitless failover; see
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. See
routing protocols that do not support hitless failover, the new master MSM removes and re-adds the
routes.

Protocol Support for Hitless Failover

Table 11 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 17, "Network
74
Description
In the fail state, the node has failed and needs to be restarted or repaired. The node reaches this
state if the system has a hardware or software failure.
In the initial state, the node is being initialized. A node stays in this state when it is coming up
and remains in this state until it has been fully initialized. Being fully initialized means that all of
the hardware has been initialized correctly and there are no diagnostic faults.
In the master state, the node is responsible for all switch management functions.
In the standby state, leader election occurs—the master and backup nodes are elected. The
priority of the node is only significant in the standby state.
"Understanding System Redundancy with Dual MSMs Installed—Modular
70, if you install two MSMs in the chassis, one assumes the role of master
"Replicating Data Between Nodes" on page
Login."
72.
Table 11 for a detailed list of protocols and their support.
Chapter 27, "OSPF" for more information. For
ExtremeWare XOS 11.3 Concepts Guide