Cabletron Systems CyberSWITCH CSX400 Installation Manual

Also see for CyberSWITCH CSX400: Setup guide Configuration guide User guide User guide User guide

Contents

Chapter 2: About the CSX4002-18CyberSWITCH CSX400 and CSX400-DC Installation GuideRedundancy VS BackupCabletron WAN devices with more than one WAN channel offer two forms of recovery fromfailure on one of the WAN channels. These two forms of recovery can best be categorized as“Redundant” and “Backup” technologies.Redundant TopologyIn the redundant topology, two channels are connected to a service such as Frame Relay at thesame time, but the router code on the device is configured in a manner to ensure that one of thesechannels is always used, unless it fails. The other channel is then available for use and the trafficswitches over automatically. In this topology, two Primary Virtual Circuits (PVCs) are used.There are no restrictions on the types of PVC physical interfaces that can be used for each channel.Any of the WPIMs supported on the Cabletron device can be used as either Primary or Redundantchannel. These include the WPIM-T1, WPIM-E1, WPIM-DDS, WPIM-SY, and the WPIM-HDSL.Over these physical connections either Point-to-Point (PPP) or Frame Relay can be selected at theData Link Layer protocol. The actual redundancy feature is based on the IP Routing protocol, soIP Routing must be used.Backup TopologyIn the Backup topology, two channels are connected, but one of them is a Switched Virtual Circuit(SVC) that is only activated upon failure of the primary channel. This primary channel is a PVCcircuit running Frame Relay or PPP. The Backup channel is either PPP running over a SyncModem which dials when this channel is activated, or is ISDN BRI (which also uses PPP as theData Link Layer protocol) but has its own digital signaling technique to activate the channel.Backup topology is suitable for WAN service which must be available, but where lower bandwidthis sufficient to meet the back up needs and cost of the backup channel is a more significant factor.When assigning backup channels, you must take into account the bandwidth of the primarychannel, and the bandwidth of the backup channel.See Appendix C for the PPP WPIM-SY modem backup configuration.