Industrial Managed
Ethernet Switch
User Manual
錯誤
!
使用
[
常用
]
索
引標籤將
Heading
1,Product Manual
套用到您想要在此處
顯示的文字。
Page
93
of
191
2.12 Spanning Tree
IEEE 802
.
1D Standard spanning tree functionality is supported by Atop
’s managed switches/ The
S
panning
T
ree
P
rotocol (
STP
) provides a function to prevent switching loops and broadcast radiation at the OSI layer 2. A switching
loop occurs in a network when there are multiple connections or redundant paths between two network switches or
at least two ports are connected on both sides of the two network switches. The switching loop can create a
broadcast radiation, which is the accumulation of broadcast and multicast traffics in a computer network
.
As
broadcast and multicast messages are forwarded by bridges/switches to every port, the bridges/switches will
repeatedly rebroadcast the broadcast messages, and this accumulation of traffic can flood the network. STP creates
a spanning tree topology and disables those links of the network that are not part of the spanning tree, which leaves
only a single active path between two nodes. This function can avoid flooding and increase network efficiency
.
Therefore, Atop
’s managed switches deploy spanning tree as a tool when the users set up connection or port
redundancy or fault-tolerance in their network.
RSTP
(
R
apid
S
panning
T
ree
P
rotocol), IEEE 802
.
1W then superseded by IEEE 802.1D-2004, is also supported in
A
TOP’s managed switches. It is an evolution of the STP, but it is still backwards compatible with standard STP.
RSTP has the advantage over the STP. When there is a topology change such as link failure in the network, the
RSTP will converge significantly faster to a new spanning tree topology. RSTP improves convergence on point-to-
point links by reducing the Max-Age time to 3 times Hello interval, removing the STP listening state, and exchanging
a handshake between two switches to quickly transition the port to forwarding state.
MSTP
(
M
ultiple
S
panning
T
ree
P
rotocol) is also a standard defined by the IEEE 802
.
1s that allows multiple VLANs
to be mapped to a single spanning tree instance called MST Instance, which will provide multiple pathways across
the network
.
It is compatible with STP and RSTP. To support larger network, MSTP groups bridges/switches into
regions that appear as a single bridge to other devices
.
Within each region, there can be multiple MST instances.
MSTP shares common parameters as RSTP such as port path costs. MSTP also help prevent switching loop and
has rapid convergence when there is a topology change. It is possible to have different forwarding paths for different
MST instances. This enables load balancing of network traffic across redundant links.
This section describes how to setup the spanning tree protocol
)
STP
(
, rapid spanning tree protocol
)
RSTP
(
, and
Multiple Spanning Tree Protocol
)
MSTP
Figure 2.103 depicts the dropdown menu for Spanning Tree
.