RuggedCom RX1000 Configuring Vrrp, Vrrp Fundamentals, Problem With Static Routing, Vrrp Solution

RuggedRouter™ User Guide

Chapter 15 – Configuring VRRP

Introduction

This chapter familiarizes the user with:

∙Configuring VRRP

∙Enabling And Starting VRRP

∙Obtaining VRRP Status

VRRP Fundamentals

The Virtual Router Redundancy Protocol (VRRP) eliminates a single point of failure associated with statically routed networks by providing automatic failover using alternate routers. The RuggedRouter VRRP daemon (keepalived) is an RFC 2338 version 2 compliant implementation of VRRP.

The Problem With Static Routing

Many network designs employ a statically configured default route in the network hosts. A static default route is simple to configure, requires little if any overhead to run and is supported by virtually every IP implementation. When dynamic host configuration protocol (DHCP) is employed, hosts may accept configuration for only a single default gateway.

Unfortunately, this approach creates a single point of failure. Loss of the router supplying the default route or the router's WAN connection results in isolating the hosts relying upon the default route.

There are a number of ways that may be used to provide redundant connections to the host. Some hosts can configure alternate gateways while others are intelligent enough to participate in dynamic routing protocols such as Routing Information Protocol (RIP) or Open Shortest Path First routing protocol (OSPF). Even when available, these approaches are not always practical due to administrative and operation overhead.

The VRRP Solution

VRRP solves the problem by allowing the establishment of a “virtual router group”, composed of a number of routers that provide a specific default route. VRRP uses an election protocol to dynamically assign responsibility for the “virtual” router to one of the routers in the group. This router is called the VRRP Master. If the Master (or optionally its WAN connection) fails, the alternate (i.e. backup) routers in the group elect a new Master. The new master provides the virtual IP address and issues a gratuitous ARP to inform the network of where the gateway can be reached.

Because the host's default route does not change and MAC address is updated, packet loss at the hosts is limited to the amount of time required to elect a new router.

VRRP Terminology

Each physical router running VRRP is known as a VRRP Router. Two or more VRRP Routers can be configured to form a “Virtual Router”. Each VRRP Router may participate in one or more Virtual Routers.

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