Spanning Tree Protocols Flashcards
Classify each STP type
802.1d Avoids a loop in the LAN
PVST Prevents loops in a VLAN
MST (802.1s) Prevents loops in an arbitrary group of VLANs
RPVST+ (802.1w) same as PVST but has faster convergence
What are the Dynamic Trunking modes
Desirable
Auto
Which dynamic trunking options will not form a trunk?
Auto-Auto
How is the root bridge elected ?
Lowest priority. The default is 32768.
The lowest base MAC address.
Command to change the vlan priority
Must be in increments of 4096
SW1(config)#spanning-tree vlan 1 priority 36864
For a vlan its default priority plus vlan #
vlan 1 priority would be 32769
Modifying port cost
SW1(config)#int gi1/1
SW1(config-if)#spanning-tree vlan 1 cost 2
Modifying port priority
SW1(config)#int gi1/1
SW1(config-if)#spanning-tree vlan 1 port-priority 64
Increments of 32
What are the STP port states ?
- Discarding
- Learning
- Forwarding
Port Roles
Root
Designated
Alternate
Backup
Root Guard
Prevents switch from becoming the root
SW1(config)#int gi1/3
SW1(config-if)#spanning-tree guard root
BPDU Guard
Error-disables port if it receives a pdu
SW1(config)#int gi1/3
SW1(config-if)#spanning-tree bpduguard enable
Global Command
spanning-tree portfast edge bpduguard default
BPDU Filter
Prevents switch from sending or processing received BPDUs.
SW1(config)#int gi1/3
SW1(config-if)#spanning-tree bpdufilter enable
UDLD modes
Automatically detect the loss of bidirectional communication on a link
Normal - Does not err disable port
udld port
Aggressive - UDLD tries to reestablish the connection with the neighbor. After eight failed retries, the port is disabled.
udld port aggressive
Global enables
udld enable
udld aggressive
Loop Guard
Blocks ports on a per-VLAN basis
SW1(config)#int gi1/3
SW1(config-if)#spanning-tree guard loop
