User`s manual

EDS-405A/408A Series User’s Manual Featured Functions
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If STP is enabled, it will detect duplicate paths and prevent, or block, one of them from forwarding
traffic. In the following example, STP determines that traffic from LAN segment 2 to LAN
segment 1 should flow through Bridges C and A as this path has a greater bandwidth and is
therefore more efficient.
What happens if a link failure is detected? As shown in next figure, the STP process reconfigures
the network so that traffic from LAN segment 2 flows through Bridge B.
STP determines which path between each bridged segment is most efficient, and then assigns a
specific reference point on the network. When the most efficient path has been identified, the other
paths are blocked. In the previous 3 figures, STP first determined that the path through Bridge C
was the most efficient, and as a result, blocked the path through Bridge B. After the failure of
Bridge C, STP re-evaluated the situation and opened the path through Bridge B.
How STP Works
When enabled, STP determines the most appropriate path for traffic through a network. The way it
does this is outlined in the following sections.
STP Requirements
Before STP can configure the network, the system must satisfy the following requirements:
y Communication between all the bridges. This communication is carried out using Bridge
Protocol Data Units (BPDUs), which are transmitted in packets with a known multicast
address.
Brid
g
e B
Brid
g
e C
LAN 1
LAN 2
LAN 3
Brid
g
e A
Brid
g
e B
Brid
g
e C
LAN 1
LAN 2
LAN 3
Brid
g
e A