Dell S4820T, Configuration Manual

Page: 993 / 1178

Te 1/7 128.264 128 20000 EDS 20000 32768 0001.e85d.0e90 128.264
Interface
Name Role PortID Prio Cost Sts Cost Link-type Edge
---------- ------ -------- ---- ------- --- ----------------
Te 1/6 Root 128.263 128 20000 FWD 20000 P2P No
Te 1/7 ErrDis 128.264 128 20000 EDS 20000 P2P No
Dell(conf-if-te-1/7)#do show ip interface brief tengigabitEthernet 1/7
Interface IP-Address OK Method Status Protocol
TenGigabitEthernet 1/7 unassigned YES Manual up up
Selecting STP Root
The STP determines the root bridge, but you can assign one bridge a lower priority to increase the
likelihood that it becomes the root bridge. You can also specify that a bridge is the root or the secondary
root.
To change the bridge priority or specify that a bridge is the root or secondary root, use the following
command.
• Assign a number as the bridge priority or designate it as the root or secondary root.
PROTOCOL SPANNING TREE mode
bridge-priority { priority-value | primary | secondary}
–
priority-value
: the range is from 0 to 65535. The lower the number assigned, the more likely
this bridge becomes the root bridge.
The primary option specifies a bridge priority of 8192.
The secondary option specifies a bridge priority of 16384.
The default is 32768 .
Example of Viewing STP Root Information
To view only the root information, use the
show spanning-tree root
command from EXEC privilege
mode.
Dell#show spanning-tree 0 root
Root ID Priority 32768, Address 0001.e80d.2462
We are the root of the spanning tree
Root Bridge hello time 2, max age 20, forward delay 15
Dell#
STP Root Guard
Use the STP root guard feature in a Layer 2 network to avoid bridging loops. In STP, the switch in the
network with the lowest priority (as determined by STP or set with the
bridge-priority
command) is
selected as the root bridge. If two switches have the same priority, the switch with the lower MAC
address is selected as the root. All other switches in the network use the root bridge as the reference
used to calculate the shortest forwarding path.
Because any switch in an STP network with a lower priority can become the root bridge, the forwarding
topology may not be stable. The location of the root bridge can change, resulting in unpredictable
Spanning Tree Protocol (STP)
993