2. Spanning Tree Protocol Flashcards
What are the different types of SPT?
- 802.1D
- PVST
- PVST+
- 802.1W RSTP
- MST
What are the 6 STP port states?
- Disabled
- Blocking (receive BPDU)
- Listening (send/receive BPDU)
- Learning (send/receive BPDU, adjust mactable)
- Forwarding
- Broken
What are the 3 STP port types?
- Root port (1 per vlan)
- Designated port (1 per link)
- Blocking port
What are the 2 types of BPDU?
- Configuration BPDU (discover the root bridge)
- Topology Change notification
How to change a switch to long mode?
spanning-tree pathcost method long
What are the long-mode costs?
- 2.000.000
- 200.000
- 20.000
- 2.000
- 1000
- 200
- 20
- 2
What does Spanning-Tree do?
Enables switches to become aware of other switches through the advertisement en receipt of BPDUs. It creates a L2 loop free topology
How can you recognize a root bridge?
All the ports are forwardering and designated
What are the root bridge election steps?
- Every switch thinks it is the root bridge and sends out a config BPDU
- If a received config BPDU has a higer bridge identifier it ignores
- If a received config BPDU has a lower bridge identifier it updates its own BPDU
If priority is equal the lowest mac address counts
Why is a bridge priority always higher?
The vlan is added to the priority
What are the 5 steps for the roort port election?
- Interface with the lowest path cost
- Interface associated to the lowest system prio of advertising switch
- Interface associated to the lowest mac of advertising switch
- When multiple links are associated to the same switch, lowest port priority
- When multiple links are associated to the same switch, lowest port number
What are the 2 port types on a catalyst switch?
- P2P
- P2P edge
What happens when a switch discovers STP topology changes?
The switch that detects the change sends a Topology Change Notification BPDU towards the bridge. An upwards stream switch will ACK and forward the BPDU.
What happens when the root bridge receives a TCN BPDU?
It creates a new BPDU configuration wit hthe Topology Change flag set. and floods it.
What does a switch do when it receives a BPDU with the Topology Flag set?
They change their MAC timer to the forward delay timer (15 sec default). This flushes all macs of devices that did not respond within the 15 sec.
After a second BPDU the MAC timer is placed back to 300