Reference Guide

Force10 Resilient Ring Protocol (FRRP) | 365

Force10 Resilient Ring Protocol (FRRP)

Force10 Resilient Ring Protocol (FRRP) is supported on the S5000 switch.

Force10 Resilient Ring Protocol (FRRP) provides fast network convergence to Layer 2 switches

interconnected in a ring topology, such as a Metropolitan Area Network (MAN) or large campuses. FRRP

is similar to what can be achieved with the Spanning Tree Protocol (STP), though even with optimizations,

STP can take up to 50 seconds to converge (depending on the size of network and node of failure) may

require 4 to 5 seconds to reconverge. FRRP can converge within 150ms to 1500ms when a link in the ring

breaks (depending on network configuration).

To operate a deterministic network, a network administrator must run a protocol that converges

independently of the network size or node of failure. FRRP is a proprietary protocol that provides this

flexibility, while preventing Layer 2 loops. FRRP provides sub-second ring-failure detection and

convergence/re-convergence in a Layer 2 network while eliminating the need for running spanning-tree

protocol. With its two-way path to destination configuration, FRRP provides protection against any single

link/switch failure and thus provides for greater network uptime.

This chapter contains the following sections:

• Protocol Overview

• Implementing FRRP

• Configuring FRRP

• Troubleshooting FRRP

• Sample Configuration and Topology

Protocol Overview

FRRP is built on a ring topology. Up to 255 rings can be configured on a system. FRRP uses one Master

node and multiple Transit nodes in each ring. There is no limit to the number of nodes on a ring. The

Master node is responsible for the intelligence of the Ring and monitors the status of the Ring. The Master

node checks the status of the Ring by sending Ring Health Frames (RHF) around the Ring from its Primary

port and returning on its Secondary port. If the Master node misses three consecutive RHFs, it determines

the ring to be in a failed state. The Master then sends a Topology Change RHF to the Transit Nodes

informing them that the ring has changed. This causes the Transit Nodes to flush their forwarding tables,

and re-converge to the new network structure.

One port of the Master node is designated the Primary port (P) to the ring; another port is designated as the

Secondary port (S) to the ring. In normal operation, the Master node blocks the Secondary port for all

non-control traffic belonging to this FRRP group, thereby avoiding a loop in the ring, like STP. Layer 2

switching and learning mechanisms operate per existing standards on this ring.