Flashcards in STP Deck (62)
What is the IEEE standard for:
What does RSTP stand for?
Rapid Spanning Tree Protocol
What STP mode do Cisco switches generally default to?
802.1D with PVST
Command to set a switch to use PVST
spanning-tree mode pvst
What 3 fields make up the BID?
2. System ID Extension
3. System ID
What is the range for priority?
What is unusual about the priority value?
It's in multiples of 4096.
What is the value of an all 1's priority field?
What are the values of each bit in the priority field?
32768 16384 8192 4096
What is normally stored in the System ID extension field?
How many bits in the System ID extension field?
How many bits in the priority field?
How many bits in the System ID field?
What's in the System ID field?
The BIA of the switch
Is the System ID configurable?
No, that's supplied automatically by the switch.
What is the decimal value of the first 2 bytes of the BID if the priority field is 0010 and the vlan is 12?
Command to set the priority for a given VLAN
spanning-tree vlan *vlan id* priority *priority*
Command to set a port cost.
spanning-tree [vlan *vlan id*] cost *cost*
What is the default BID priority?
Is portfast or bpduguard enabled by default?
What are the 3 port types in STP?
1. Root port
2. Designated port
3. Blocking port
What is a Designated port vs other port types?
It's a port that is not the closest to the root switch (root port), but is still forwarding and not blocking (blocking port). This is also related to the fact that this port is where the root switch's BPDU will be forwarded out of.
What state are all the ports on the root switch in?
They are all forwarding.
What types of ports (in STP language) does the root switch have: root, designated, blocking, disabled.
What 4 fields are shown in a "show mac address-table" output?
2. MAC address
3. Type (dynamic or static)
4. Output port to get to that MAC
What does "show interfaces status" show us (7 fields)?
3. Status (connect / notconnect/ disabled)
7. Type (10/100/1000 TX etc)
If a frame came into a switch and was either an unknown destination MAC or a broadcast mac, what ports would the switch forward it out of?
All forwarding ports for that VLAN, except the one on which it was received.
What makes a switch a designated switch for a given ethernet segment?
It's the switch (and therefor the port) that is forwarding the root's BPDU.
4 important fields in a Hello BPDU
1. Root BID
2. Sender's BID
3. Sender's root cost
4. Timers on the root switch