Network Redundancy; Stp - Delta DVS-328 series User Manual

D V S M a n a g e d I n d u s t r i a l R a c k Mo u n t E t h e r n e t S wi t c h U s e r Ma n u a l

3.3 Network Redundancy

In some network environments, users need to set up redundant loops in the network to provide a backup path
for disconnection or a network device breakdown. But if there are many network devices in the network, then
each host needs to spend more time and cross many network devices to associate with each other. And
sometimes the disconnection happens in a busy network, so the network must recover in a short time. Setting
up redundancy on your network helps protect critical links against failure, protects against network loops, and
keeps network downtime at a minimum. For example, if the Delta switch is used as a key communication
component of a production line, several minutes of downtime may cause a big loss in production and revenue.
IMPORTANT:
Make sure that you save the configuration in the Save Configuration
page after you have applied the configuration changes. (Save
ConfigSave Configuration) If you do not save the configuration,
then the configuration will be cleared after the switch is rebooted.

3.3.1 STP

Spanning Tree Protocol (STP) provides a tree topology that helps reduce link failure in a network, find one path
between end devices and protect loops in the network. Bridge Protocol Data Unit (BPDU) includes the
calculation of information and it is used to negotiate between switches and establish STP. STP is a bridge
based system and it defines 5 kinds of port statuses: blocking, listening, learning, forwarding and disabling. If
the status of the blocking changes to forwarding, STP needs to spend more than 30 seconds.
Rapid Spanning Tree Protocol (RSTP) was defined by IEEE in 2001. RSTP provides faster tree convergence
after a topology changes. Sometimes it only needs to spend a few hundred milliseconds. And RSTP can be
backward compatible with standard STP.
The Delta switch supports different protocols to support communication redundancy. When configuring a
redundant ring, all switches on the same ring must be configured to use the same redundant protocol.
STP/RSTP can let you establish a redundant ring and protect the loop in a network, as shown in the figure
below.
If STP/RSTP is enabled, it will detect duplicate paths, calculate the cost of each path and block the lowest cost
path (ex. the path between A and C) from forwarding traffic. So bridges can communicate with each other
without loops, as shown in the figure below.
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