FRNT HowTo

About

This document details some common use-cases for FRNT and how to configure them.

For an overview of available configuration settings for FRNT refer to the configuration guide:

FRNT Configuration Guide

Introduction

The Fast Reconfiguration Network Topology Protocol (FRNT) handles fast reconfiguration in switched ring topologies. One of the switches has the role of FRNT focal point while the other switches are referred to as FRNT members. When the switches are connected in a ring, it is the responsibility of the focal point to break the loop by putting one of its ports (port ”M”) in blocking mode. When choosing FRNT ports, fixed speed and full duplex is recommended and also to avoid copper SFPs.

For information about using FRNT together with DHCP functionality in order to create a redundant network setup with dynamic address allocation, see:

DHCP Relay Server Ring

Single ring

The topology presented in this example consists of four different devices that create a redundant ring setup.

       .-------.               .-------.
       |       |M             N|       |
       |  S1   +-||------------+  S2   |
       |     fp|1             2|       |
       '---+---'               '---+---'
          2|N                     1|M
           |         FRNT          |
          1|M                     2|N
       .---+---.               .---+---.
       |       |N             M|       |
       |  S4   +---------------+  S3   |
       |       |2             1|       |
       '-------'               '-------'

Figure 1: FRNT network operating in ring mode.

Configuration

Set up the focal point:

S1:/#> configure
S1:/config/#> ring
S1:/config/ring/#> frnt
S1:/config/ring/frnt/#> ports eth1, eth2
S1:/config/ring/frnt/#> leave
S1:/#>

Set up rest of the devices (S2 - S4), which aren’t focal points

Sx:/#> configure
Sx:/config/#> ring
Sx:/config/ring/#> frnt
Sx:/config/ring/frnt/#> no focal
Sx:/config/ring/frnt/#> ports eth1, eth2
Sx:/config/ring/frnt/#> leave
Sx:/#>

Note

Double ring is not yet supported

Bus

The main use case for configuring an FRNT bus is to achieve a horseshoe topology, by using the FRNT bus together with Ring Coupling. On the bus edges, only use port M.

  .-------.             .-------.             .-------.             .-------.
  |       |M           N|       |M           N|       |M           M|       |
  |  S1   +-||----------+  S2   +-------------+  S3   +-------------+  S4   |
  |     fp|1           2|       |1           2|       |1           2|       |
  '-------'             '-------'             '-------'             '-------'

Figure 2: FRNT network operating in bus mode.

Configuration

Set up the focal point:

S1:/#> configure
S1:/config/#> ring
S1:/config/ring/#> frnt
S1:/config/ring/frnt/#> ports eth1
S1:/config/ring/frnt/#> leave
S1:/#>

Set up rest of the devices (S2 - S3), which aren’t focal points

Sx:/#> configure
Sx:/config/#> ring
Sx:/config/ring/#> frnt
Sx:/config/ring/frnt/#> no focal
Sx:/config/ring/frnt/#> ports eth1, eth2
Sx:/config/ring/frnt/#> leave
Sx:/#>

Lastly set up the device that is at the end of the bus:

S4:/#> configure
S4:/config/#> ring
S4:/config/ring/#> frnt
S4:/config/ring/frnt/#> no focal
S4:/config/ring/frnt/#> ports eth2
S4:/config/ring/frnt/#> leave
S4:/#>