Edge-Core ECS4110-28T, Руководство по управлению, Страница: 252 / 1514

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HAPTER
8
| Spanning Tree Algorithm
Configuring Interface Settings for STA
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Auto – The switch automatically determines if the interface is
attached to a point-to-point link or to shared media. (This is the
default setting.)
◆
Root Guard – STA allows a bridge with a lower bridge identifier (or
same identifier and lower MAC address) to take over as the root bridge
at any time. Root Guard can be used to ensure that the root bridge is
not formed at a suboptimal location. Root Guard should be enabled on
any designated port connected to low-speed bridges which could
potentially overload a slower link by taking over as the root port and
forming a new spanning tree topology. It could also be used to form a
border around part of the network where the root bridge is allowed.
(Default: Disabled)
◆ Admin Edge Port – Since end nodes cannot cause forwarding loops,
they can pass directly through to the spanning tree forwarding state.
Specifying Edge Ports provides quicker convergence for devices such as
workstations or servers, retains the current forwarding database to
reduce the amount of frame flooding required to rebuild address tables
during reconfiguration events, does not cause the spanning tree to
initiate reconfiguration when the interface changes state, and also
overcomes other STA-related timeout problems. However, remember
that Edge Port should only be enabled for ports connected to an end-
node device. (Default: Auto)
■
Enabled – Manually configures a port as an Edge Port.
■
Disabled – Disables the Edge Port setting.
■
Auto – The port will be automatically configured as an edge port if
the edge delay time expires without receiving any RSTP or MSTP
BPDUs. Note that edge delay time (802.1D-2004 17.20.4) equals
the protocol migration time if a port's link type is point-to-point
(which is 3 seconds as defined in IEEE 802.3D-2004 17.20.4);
otherwise it equals the spanning tree’s maximum age for
configuration messages (see maximum age under "Configuring
Global Settings for STA" on page 243 ).
An interface cannot function as an edge port under the following
conditions:
■
If spanning tree mode is set to STP ( page 243 ), edge-port mode
cannot automatically transition to operational edge-port state using
the automatic setting.
■
If loopback detection is enabled ( page 242 ) and a loopback BPDU is
detected, the interface cannot function as an edge port until the
loopback state is released.
■
If an interface is in forwarding state and its role changes, the
interface cannot continue to function as an edge port even if the
edge delay time has expired.