Managing Module Redundancy; Chapter 3 Managing Stateful Srp Switchover; Chapter 4 Configuring A Unified In-Service Software Upgrade; Configuring Vrrp - Juniper SERVICE AVAILABILITY - CONFIGURATION GUIDE V 11.1.X Configuration Manual

JUNOSe 11.1.x Service Availability Configuration Guide
When you perform a unified ISSU on a router that has one or more modules that do
not support unified ISSU, these modules are upgraded by means of the legacy,
conventional upgrade process. The unsupported modules undergo a cold reboot at
the beginning of the unified ISSU process, and are held down until the ISSU process
is completed.

VRRP

Virtual Router Redundancy Protocol (VRRP) prevents loss of network connectivity
to end hosts when the static default IP gateway fails. By implementing VRRP, you
can designate a number of routers as backup routers in the event that the default
master router fails. In case of a failure, VRRP dynamically shifts the packet-forwarding
responsibility to a backup router. VRRP creates a redundancy scheme that enables
hosts to keep a single IP address for the default gateway but maps the IP address to
a well-known virtual MAC address. You can take advantage of the redundancy
provided by VRRP without performing any special configuration on the end host
systems.
Routers running VRRP dynamically elect master and backup routers. You can also
force assignment of master and backup routers using priorities in the range 1–255,
with 255 being the highest priority.
VRRP supports virtual local area networks (VLANs), stacked VLANs (S-VLANs), and
creation of interchassis redundancy (ICR) partitions.

Interchassis Redundancy

ICR enables you to minimize subscriber downtime when the router or access interface
on the edge router fails. ICR accomplishes this by re-creating subscriber sessions on
the backup router that were originally terminated on the failed router. It also enables
you to track the failure of uplink interfaces. In this way, ICR enables you to completely
recover from router failure. ICR uses Virtual Router Redundancy Protocol (VRRP) to
detect failures. ICR also enables you to track the failure of uplink interfaces. ICR
currently supports only PPPoE subscribers.
Related Topics
6
Understanding Service Availability Features
Managing Module Redundancy on page 7
Managing Stateful SRP Switchover on page 25
Configuring a Unified In-Service Software Upgrade on page 57
Configuring VRRP on page 105
Managing Interchassis Redundancy on page 127
Service Availability Overview on page 3