Understanding EX8216 Switch Component and Functionality Redundancy

The Juniper Networks EX8216 Ethernet Switch is available as a fully redundant system. A redundant EX8216 switch configuration is designed so that no single point of failure can cause the entire switch to fail. See EX8216 Switch Configurations.

Hardware Components That Provide Redundancy

The following hardware components provide redundancy to a Juniper Networks EX8216 Ethernet switch:

• Routing Engine (RE) modules—An EX8216 switch can have either one RE module or two RE modules. If two RE modules are installed, one RE module functions as the master and the other functions as the backup. If the master RE module fails or is removed, the backup module takes over as the master RE module.

  When the RE modules are configured for graceful switchover, the backup RE module automatically synchronizes its configuration and state with those of the master RE module. Any update to the master RE module is replicated on the backup RE module. If the backup module assumes mastership, packet forwarding continues through the switch.

• Power supplies—You can install up to six AC or six DC power supplies in an EX8216 switch. Each power supply connects to the midplane of the chassis, which distributes the output power produced by the power supplies to different switch components. (See Midplane in an EX8216 Switch.) Each power supply provides power to all the components in the switch.

  An N+1 power configuration is required for EX8200 switches. In an N+1 power configuration, if one power supply fails or is removed, the remaining power supplies continue to supply power for the entire system without interruption. If dual power feed redundancy is required, the required power configuration is N+N. The maximum internal power consumption for the EX8216 switch must be kept below 9000 W for a six power supply configuration (3+3) when 3000 W AC power supplies are used. The DC power supplies provide independent A and B power feeds so dual power redundancy is available even in an N+1 power configuration. See AC Power Supply in an EX8200 Switch and DC Power Supply in an EX8200 Switch.

• Cooling system—The cooling system in an EX8216 switch consists of two identical and interchangeable fan trays. Each fan tray has nine fans and two fan tray controllers.

  The fans in each fan tray are controlled by the two fan tray controllers. The fans are numbered 1 through 9. Fans 1 through 5 are controlled by the first fan tray controller. Fans 6 through 9 are controlled by the second fan tray controller. If one fan tray controller fails, the other fan tray controller keeps the remaining fans working. This allows the switch to continue to operate normally.

  Each fan tray continues to operate indefinitely and provide sufficient cooling even when a single fan fails provided the room temperature is within the operating range. See Cooling System and Airflow in an EX8216 Switch.

Routing Engine and Control Redundancy

Each RE module contains Routing Engine circuitry, and system control and management circuitry. An EX8216 switch can have one RE module or two RE modules. If a switch has two RE modules, one functions as the master while the other functions as a backup and is in standby mode. This provides the switch with full redundancy (1+1) for Routing Engine and system control functionality.

Table 1 lists the RE module slots in the EX8216 chassis and the Routing Engine and system control redundancy associated with different RE module combinations.

Switch Fabric Redundancy

The switch fabric circuitry in an EX8216 switch is distributed across eight Switch Fabric (SF) modules. We recommend that you install all eight SF modules in an EX8216 switch to support maximum midplane performance for the installed line cards.

All SF modules are fully connected to all installed line cards. When the switch is operational, all eight SF modules are simultaneously active. If a single SF module fails, the input/output traffic for that module is load-balanced among the remaining SF modules, providing graceful degradation in midplane performance. The impact of an SF module failure on the performance of an EX8216 switch varies based on the type of line cards installed in the switch and the traffic mix flowing through them. In an EX8216 switch configuration that is fully loaded with 8-port 10-Gigabit Ethernet SFP+ line cards, if one SF module fails, the remaining seven SF modules still have sufficient switching capacity to maintain continuous switch operation at full wire-rate performance.

Table 2 lists the SF module slots in an EX8216 chassis and shows that switch fabric redundancy is associated with both base and redundant switch configurations.