Redundant Routing Engines; Virtual Chassis; Graceful Routing Engine Switchover - Juniper JUNOS OS 10.4 - FOR EX REV 1 Manual

Complete Software Guide for Junos

Redundant Routing Engines

Virtual Chassis

Graceful Routing Engine Switchover

24
®
OS for EX Series Ethernet Switches, Release 10.4
On the switches, graceful protocol restart can be applied to aggregate and static routes
and for routing protocols (BGP, IS-IS, OSPF, and RIP).
Graceful protocol restart works similarly for the different routing protocols. The main
benefits of graceful protocol restart are uninterrupted packet forwarding and temporary
suppression of all routing protocol updates. Graceful protocol restart thus allows a switch
to pass through intermediate convergence states that are hidden from the rest of the
network. Most graceful restart implementations define two types of switches—the
restarting switch and the helper switch. The restarting switch requires rapid restoration
of forwarding state information so that it can resume the forwarding of network traffic.
The helper switch assists the restarting switch in this process. Individual graceful restart
configuration statements typically apply to either the restarting switch or the helper
switch.
Redundant Routing Engines are two Routing Engines that are installed in a switch. When
a switch has two Routing Engines, one functions as the master, while the other stands
by as a backup should the master Routing Engine fail. Redundant Routing Engines are
supported on Juniper Networks EX8200 Ethernet Switches.
The master Routing Engine receives and transmits routing information, builds and
maintains routing tables, communicates with interfaces and Packet Forwarding Engine
components of the switch, and has full control over the control plane of the switch.
The backup Routing Engine stays in sync with the master Routing Engine in terms of
protocol states, forwarding tables, and so forth. If the master becomes unavailable, the
backup Routing Engine takes over the functions that the master Routing Engine performs.
Network reconvergence takes place more quickly on switches with redundant Routing
Engines than on switches with a single Routing Engine.
A Virtual Chassis is multiple switches connected together that operate as a single network
entity. The advantages of connecting multiple switches into a Virtual Chassis include
better-managed bandwidth at a network layer, simplified configuration and maintenance
because multiple devices can be managed as a single device, and a simplified Layer 2
network topology that minimizes or eliminates the need for loop prevention protocols
such as Spanning Tree Protocol (STP). A Virtual Chassis improves high availability by
introducing a variety of failover mechanisms; if a member switch, a line card, or an interface
fails on a switch that is a member of a Virtual Chassis, for instance, traffic to that switch,
line card, or interface can be rerouted within the Virtual Chassis.
Juniper Networks EX4200 Ethernet Switches or EX8200 switches can form a Virtual
Chassis.
You can configure graceful Routing Engine switchover (GRES) on a switch with redundant
Routing Engines or on a Virtual Chassis, allowing control to switch from the master
Routing Engine to the backup Routing Engine with minimal interruption to network
Copyright © 2010, Juniper Networks, Inc.