Juniper JUNOS OS 10.4 - FOR EX REV 1 Manual page 1180

Complete Software Guide for Junos
Role of XRE200 External Routing Engine Redundancy in a Virtual Chassis Topology
EX8200 Virtual Chassis Basic Topology
1076
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OS for EX Series Ethernet Switches, Release 10.4
Figure 25 on page 1076 shows a ring EX8200 Virtual Chassis topology.
Figure 25: EX8200 Virtual Chassis Ring Topology
VCCP traffic often has to travel multiple hops to communicate with other devices in the
Virtual Chassis. When a VCP link fails in a ring topology, additional hops are added for
VCCP traffic in the Virtual Chassis ring topology. VCP link failures are problematic in a
ring topology, as the shortage of VCP links in the topology increases the potential for a
single link failure to cause the EX8200 member switches to split from the Virtual Chassis.
An EX8200 Virtual Chassis full mesh topology is always recommended. Use the ring
topology in cases where some of the VCP links in a full mesh topology have failed or
when the equipment to configure a full mesh topology is unavailable.
A backup XRE200 External Routing Engine provides redundancy to a master XRE200
External Routing Engine. If a master external Routing Engine fails for any reason, the
backup external Routing Engine takes control of the Virtual Chassis, allowing network
traffic to continue to pass through the Virtual Chassis with minimal network disruption.
NOTE: A backup XRE200 External Routing Engine is recommended in all
EX8200 Virtual Chassis configurations.
When a backup external Routing Engine is used in the EX8200 Virtual Chassis, one link
must be used to connect the master external Routing Engine to the backup external
Routing Engine. Both EX8200 switches must also have connections to the backup external
Routing Engine.
The most basic EX8200 Virtual Chassis topology has one XRE200 External Routing
Engine connecting two EX8200 switches into a Virtual Chassis.
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