Host Redundancy Overview

You monitor redundant Routing Engines, host modules, and host subsystems to provide a standby Routing Engine and controller component that will switch from standby to active, assuming mastership, with limited running downtime when a failure occurs.

This chapter provides an overview of how redundant host modules, host subsystems, and Routing Engines work on various routing platforms. Additionally, it describes the topics as listed in Table 106.

Table 106: Checklist for Host Redundancy

Monitor Redundant Routing Engine Tasks	Command or Action
Understanding Redundancy for the Routing Engine, Host Module, and Host Subsystem M10i Router Redundant Routing Engines and HCMs M20 Router Redundant Routing Engines and SSBs M40e and M160 Router Redundant Host Modules M320 Router, T320 Router, and T640 Routing Node Redundant Host Subsystems
Routing Engine, Host Module, and Host Subsystem Redundancy Connections Redundancy Connection for an M10i Router Redundancy Connection for an M20 Router Redundancy Connection for an M40e or M160 Router Redundancy Connection for an M320 Router Redundancy Connection for a T320 Router and T640 Routing Node
Determining Which Routing Engine You Are Logged In To
Display Routing Engine Status	show chassis routing-engine
Display the Router Hardware	show chassis hardware
Determining Routing Engine Mastership
Determine the Routing Engine Mastership By Checking Status	show chassis routing-engine
Determine Routing Engine Mastership By Checking the LEDs	Physically check the LEDs on either the craft interface or the Routing Engine (depending on which chassis the Routing Engine is installed).
Log In To Backup Routing Engine If graceful-switchover is Configured	request routing-engine login other-routing-engine
Manually Configuring Master and Backup Routing Engines	For slot 0: [edit] set chassis redundancy routing-engine 1 master commit For slot 1: [edit] set chassis redundancy routing-engine 0 backup commit
Manually Switching Routing Engine Mastership	request chassis routing-engine master (acquire | release | switch)
Determining Why Mastership Switched	show log mastership
Configuring the Backup Routing Engine to Assume Mastership on Failure of Keepalives	[edit] set chassis redundancy failover on-loss-of-keepalives set chassis redundancy keepalive-time 300 commit
Avoiding Redundancy Problems
Operate the Same Type of Routing Engine and JUNOS Software	The active and standby Routing Engines must be the same type of Routing Engine and must operate the same version of JUNOS software.
Use the Groups Configuration	[edit] set groups group-name
Synchronize Configurations	[edit] commit synchronize
Copy a Configuration File from One Routing Engine to Another	file copy <source> <destination>
Use the Proper Shutdown Process on a Backup Routing Engine	request system halt

See Also

• Monitoring Redundant MCSs
• Monitoring Redundant Routing Engines
• Monitoring Redundant Control Boards