Viewing Routing Engine Switchover Indicators in the Chassis Image
Redundant Routing Engines are two Routing Engines that are installed in the same routing platform. One functions as the primary, while the other stands by as a backup should the primary Routing Engine fail. On routing platforms with dual Routing Engines, network reconvergence takes place more quickly than on routing platforms with a single Routing Engine.
The Chassis View provides a pictorial representation of the chassis or device, and the modules or components that are installed in it, such as the line cards, interfaces, and other hardware elements. To view a pictorial representation of a device chassis and the configured components, such as interfaces, line cards, and hardware elements, select a managed device listed in the My Network tree in Device View of Build mode of the Connectivity Services Director GUI, and select Device Management > View Physical Inventory from the tasks pane.
The active or primary and the standby or backup Routing Engines indicated on the Routing Engine in the Chassis View with a descriptive text label. “ACT” denotes an active Routing Engine, whereas “SDBY” denotes a standby Routing Engine. The status is updated on the Routing Engine only after a polling request because of the implications on the Junos Space application and device performance.
Routing Engine Redundancy Overview
When a Routing Engine is configured as primary, it has full functionality. It receives and transmits routing information, builds and maintains routing tables, communicates with interfaces and Packet Forwarding Engine components, and has full control over the chassis. When a Routing Engine is configured to be the backup, it does not communicate with the Packet Forwarding Engine or chassis components.
On devices running Junos OS Release 8.4 or later, both Routing Engines cannot be configured to be primary at the same time. This configuration causes the commit check to fail.
A failover from the primary Routing Engine to the backup Routing Engine occurs automatically when the primary Routing Engine experiences a hardware failure or when you have configured the software to support a change in primary role based on specific conditions. You can also manually switch Routing Engine primary role by issuing one of the request chassis routing-engine commands. In this topic, the term failover refers to an automatic event, whereas switchover refers to either an automatic or a manual event.
When a failover or a switchover occurs, the backup Routing Engine takes control of the system as the new primary Routing Engine.
If graceful Routing Engine switchover is not configured, when the backup Routing Engine becomes primary, it resets the switch plane and downloads its own version of the microkernel to the Packet Forwarding Engine components. Traffic is interrupted while the Packet Forwarding Engine is reinitialized. All kernel and forwarding processes are restarted.
If graceful Routing Engine switchover is configured, interface and kernel information is preserved. The switchover is faster because the Packet Forwarding Engines are not restarted. The new primary Routing Engine restarts the routing protocol process (rpd). All hardware and interfaces are acquired by a process that is similar to a warm restart.
If graceful Routing Engine switchover and nonstop active routing (NSR) are configured, traffic is not interrupted during the switchover. Interface, kernel, and routing protocol information is preserved.
If graceful Routing Engine switchover and graceful restart are configured, traffic is not interrupted during the switchover. Interface and kernel information is preserved. Graceful restart protocol extensions quickly collect and restore routing information from the neighboring routers.
Conditions That Trigger a Routing Engine Failover
The following events can result in an automatic change in Routing Engine primary role, depending on your configuration:
The routing platform experiences a hardware failure. A change in Routing Engine primary role occurs if either the Routing Engine or the associated host module or subsystem is abruptly powered off. You can also configure the backup Routing Engine to take primary role if it detects a hard disk error on the primary Routing Engine.
The routing platform experiences a software failure, such as a kernel crash or a CPU lock. You must configure the backup Routing Engine to take primary role when it detects a loss of keepalive signal.
A specific software process fails. You can configure the backup Routing Engine to take primary role when one or more specified processes fail at least four times within 30 seconds.
If any of these conditions is met, a message is logged and the backup Routing Engine attempts to take primary role. By default, an alarm is generated when the backup Routing Engine becomes active. After the backup Routing Engine takes primary role, it continues to function as primary even after the originally configured primary Routing Engine has successfully resumed operation. You must manually restore it to its previous backup status. (However, if at any time one of the Routing Engines is not present, the other Routing Engine becomes primary automatically, regardless of how redundancy is configured.)