37 terms

1 STP

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STP convergence time
30-second
STP convergence via States?
The listening and learning states
How will STP designated port must be elected on the segment connecton
ill be the port with the lowest root path cost of all the ports on that segment
What are the STP port States?
STP port States

STP: disabled
blocking(BLK)
listening (LIS)
learning(LER)
forwarding(FWD)
STP PATH COST for 1 Gbps
Cost 4
STP PATH COST 622 MBPS
COST 6
STP PATH COST 155 Mbps
Cost 14
STP PATH COST 100 Mbps
100 Mbps Cost 19
STP PATH COST 45 Mbps
Cost 39
STP PATH COST 16 Mbps
Cost 62
STP PATH COST 10 Mbps
Cost 100
STP PATH COST 4 Mbps
Cost 250
STP port state disabled show the port as?
STP port state Once that port is administratively enabled, the port goes into blocking state (BLK).
You won't see "DIS" next to a port in the output of show spanning vlan.disabled port is simply a port that's been administratively shut down. A disabled port isn't forwarding frames or even officially running STP.
STP port state blocking
No frame forwarding, no frame receiving, and therefore no dynamic learning of MAC addresses. About the only thing a blocked port can do is accept BPDUs from neighboring switches.
STP port state forwarding
When a port starts the transition from blocking to forwarding, it enters listening mode (LIS).
The port goes from learning to forwarding mode. Forwarding mode allows a port to
The port goes from learning to forwarding mode. Forwarding mode allows a port to forward and receive frames, send and receive BPDUs, and continue to learn MAC addresses. This is the only state where the port is actually forwarding frames!
STP Hello Time defines
Hello Time defines how often the root bridge originates Config BPDUs.
Default setting: 2 seconds.
What is a Forward Delay
is the length of the listening and learning port stages, with a default of 15 seconds for each individual stage.
STP Timers
Maximum Age (Max Age) is how long a switch will retain the superior BPDU's contents before discarding it. Default setting: 20 seconds.
STP Timers must be set under the
Root Switch
L3 routing protocols such as EIGRP and OSPF allow us to use how many paths?
to the primary paths, making equal- and unequal-cost load balancing possible. With routing, we want to use as many of those paths as is feasible.
purpose of the Spanning Tree Protocol (STP)
Is to identify valid loop-free paths and then choose the best of those paths for use. STP will then block ports on the valid but less desirable paths, holding those paths in standby. Should a primary path become unavailable, STP will realize this and begin to unblock the necessary ports to put the next best path into action.
Before making a forwarding decision regarding the incoming frame, each switch will an entry
check its own MAC address table regarding an entry for the source MAC address of the frame. None of the switches have such
Forwarding decision None of the switches have an entry for the frame's destination.
They'll flood the frame out all ports except the one it came in on. so each switch will follow the default behavior for an unknown unicast address.
switching loops cause three major problems:
Frames can't reach their intended destination,either in full or in part There's an unnecessary strain put on the switch CPU A lot of bandwidth is unnecessarily sucked up by all those broadcasts
What is a Forward Delay default timer
Default of 15 seconds for each individual stage.
STP port state disabled
You won't see "DIS" next to a port in the output of show spanning vlan.disabled port is simply a port that's been administratively shut down. A disabled port isn't forwarding frames or even officially running STP.
listening mode (LIS).
When a port starts the transition from blocking to forwarding, it enters listening mode (LIS).
STP port state listening (LIS)
A listening port is listening for BPDUs. A listening port can send BPDUs as well, allowing the port to participate in the root bridge election. A port in listening mode still can't forward or receive frames, and as a result the port can't learn MAC addresses.
STP port state learning (LRN)
A learning port isn't forwarding frames, but it is learning MAC addresses and adding them to the switch's MAC address table. A port in learning mode continues to send and receive BPDUs.
STP port state
the port goes from learning to forwarding mode. Forwarding mode allows a port to forward and receive frames, send and receive BPDUs, and continue to learn MAC addresses. This is the only state where the port is actually forwarding frames!
STP port root port selection
First, choose the port receiving the superior BPDU. Tie? Choose the port with the lowest root path cost.Still tied? Choose the port receiving the BPDU with the lowest Sender BID.
Hello Time defines how often the
Hello Time defines how often the root bridge originates Config BPDUs. Default setting: 2 seconds.
Maximum Age (Max Age) is?
How long a switch will retain the superior BPDU's contents before discarding it. Default setting: 20 seconds.
STP Timers must be set under the
Root Switch
Spanning tree IEEE Priority
is 32769
purpose of the Spanning Tree Protocol (STP)
is to identify valid loop-free paths and then choose the best of those paths for use. STP will then block ports on the valid but less desirable paths, holding those paths in standby. Should a primary path become unavailable, STP will realize this and begin to unblock the necessary ports to put the next best path into action.
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