Enterasys csx400 Installationsanweisungen
Chapter 2: About the CSX400
2-18
CyberSWITCH CSX400 and CSX400-DC Installation Guide
Redundancy VS Backup
Cabletron WAN devices with more than one WAN channel offer two forms of recovery from
failure on one of the WAN channels. These two forms of recovery can best be categorized as
“Redundant” and “Backup” technologies.
failure on one of the WAN channels. These two forms of recovery can best be categorized as
“Redundant” and “Backup” technologies.
Redundant Topology
In the redundant topology, two channels are connected to a service such as Frame Relay at the
same time, but the router code on the device is configured in a manner to ensure that one of these
channels is always used, unless it fails. The other channel is then available for use and the traffic
switches over automatically. In this topology, two Primary Virtual Circuits (PVCs) are used.
same time, but the router code on the device is configured in a manner to ensure that one of these
channels is always used, unless it fails. The other channel is then available for use and the traffic
switches 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 Redundant
channel. 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 the
Data Link Layer protocol. The actual redundancy feature is based on the IP Routing protocol, so
IP Routing must be used.
Any of the WPIMs supported on the Cabletron device can be used as either Primary or Redundant
channel. 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 the
Data Link Layer protocol. The actual redundancy feature is based on the IP Routing protocol, so
IP Routing must be used.
Backup Topology
In 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 PVC
circuit running Frame Relay or PPP. The Backup channel is either PPP running over a Sync
Modem which dials when this channel is activated, or is ISDN BRI (which also uses PPP as the
Data Link Layer protocol) but has its own digital signaling technique to activate the channel.
(SVC) that is only activated upon failure of the primary channel. This primary channel is a PVC
circuit running Frame Relay or PPP. The Backup channel is either PPP running over a Sync
Modem which dials when this channel is activated, or is ISDN BRI (which also uses PPP as the
Data 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 bandwidth
is 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 primary
channel, and the bandwidth of the backup channel.
is 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 primary
channel, and the bandwidth of the backup channel.
See
for the PPP WPIM-SY modem backup configuration.