ZyXEL Communications 35 Series, 70 Series 6.1 Bridge Loop, 6.2 Spanning Tree Protocol (STP)

ZyWALL 5/35/70 Series User’s Guide

CHAPTER 6

Bridge Screens

This chapter describes how to configure bridge settings. This chapter is only applicable when the ZyWALL is in bridge mode.

6.1 Bridge Loop

The ZyWALL can act as a bridge between a switch and a wired LAN or between two routers.

Be careful to avoid bridge loops when you enable bridging in the ZyWALL. Bridge loops cause broadcast traffic to circle the network endlessly, resulting in possible throughput degradation and disruption of communications. The following example shows the network topology that can lead to this problem:

•If your ZyWALL (in bridge mode) is connected to a wired LAN while communicating with another bridge or a switch that is also connected to the same wired LAN as shown next.

Figure 42 Bridge Loop: Bridge Connected to Wired LAN

To prevent bridge loops, ensure that your ZyWALL is not set to bridge mode while connected to two wired segments of the same LAN or you enable RSTP in the Bridge screen.

6.2 Spanning Tree Protocol (STP)

STP detects and breaks network loops and provides backup links between switches, bridges or routers. It allows a bridge to interact with other STP-compliant bridges in your network to ensure that only one route exists between any two stations on the network.

Chapter 6 Bridge Screens 122