Spanning-Tree Root-Guard - Edge-Core ES3510MA Management Manual

| Spanning Tree Commands
C 33
HAPTER
spanning-tree root-
guard
C U
OMMAND SAGE
◆ This command defines the priority for the use of a port in the Spanning
Tree Algorithm. If the path cost for all ports on a switch are the same,
the port with the highest priority (that is, lowest value) will be
configured as an active link in the spanning tree.
◆ Where more than one port is assigned the highest priority, the port with
lowest numeric identifier will be enabled.
E
XAMPLE
Console(config)#interface ethernet 1/5
Console(config-if)#spanning-tree port-priority 0
R C
ELATED OMMANDS
spanning-tree cost (769)
This command prevents a designated port
into account and allowing a new STP root port to be elected. Use the no
form to disable this feature.
S
YNTAX
[no] spanning-tree root-guard
D S
EFAULT ETTING
Disabled
C M
OMMAND ODE
Interface Configuration (Ethernet, Port Channel)
C U
OMMAND SAGE
A bridge with a lower bridge identifier (or same identifier and lower
◆
MAC address) can take over as the root bridge at any time.
When Root Guard is enabled, and the switch receives a superior BPDU
◆
on this port, it is set to the Discarding state until it stops receiving
superior BPDUs for a fixed recovery period. While in the discarding
state, no traffic is forwarded across the port.
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.
◆ When spanning tree is initialized globally on the switch or on an
interface, the switch will wait for 20 seconds to ensure that the
spanning tree has converged before enabling Root Guard.
"Displaying Interface Settings for STA" on page
14. See Port Role under
– 776 –
from taking superior BPDUs
14
207.