Hello, friends welcome to my blog tutorials my name is Dinesh Kumar Gupta in the last tutorials we discuss inter-VLAN.
now today I will discuss that What is Spanning Tree Protocol? STP terms?
So let's understand...
What is Spanning Tree Protocol?
STP:- Stand for Spanning Tree Protocol that provides the loop-free network when you have multiple links between the switch and also provides redundancy.
It is an Open Standard Protocol (IEEE 802.1D)
STP stop the broadcast Strome, multiple frames copies & database instability.
By default, STP runs all Cisco Catalyst Switch.
STP Terms
(1) Root Bridge
(2) Root Port
(3) Blocking Port
(4) Forwarding Port
(5) Designated Port
How STP works
(1) Root Bridge:- First of all selecting the one Root Bridge into all switches witch the help of priority value (by default priority value of every switch 32768+1 (vlan 1 ) =32769) and MAC address
Bridge ID = least of priority value+MAC address.
out of all the switches in the network one is elected as a Root bridge that became the focal point in the network switches and all the frame transfer one point to another point.
One is Root Bridge and all Non-Root bridge.
we can see the bridge ID of every switch
Show command is
Switch#show spanning-tree
(2) Root Port:-After selecting the Root Bridge now selecting the Root Port the Root Port shortest path Every Non-Root Bridge looks the best way to go Root Bridge.
but how to finds the best way? just Three measurements.
(a) Lest Cost (Speed)
(b) The lowest Forwarding Switch ID
(c) Lowest Physical port Number
STP Port Cost
Link Bandwidth STP Cost
4 Mbps 250
10 Mbps 100
16 Mbps 62
45 Mbps 39
100 Mbps 19
155 Mbps 14
622 Mbps 6
1 Gbps 4
10 Gbps 2
(3) Blocking Port:- That port that is used to disabled the loops.
There are two of Port in a Network
(a) Forwarding Port:- Forwarding Port always enable. this port never is disabled.
in this data send and received.
(b) Blocking Port:- Non-Forwarding that means in this port can't forward the data.
STP Port State
Port time
Blocking 20 sec. or no limits
Listening 15 sec.
Learning 15 sec.
Forwarding no limit
Disable no limit
What is Portfast?
Portfast is a feature of Cisco Devices that are used to disable STP and it is used to reduce the conversion time. when we connect the end user device the conversion time reduce.
but if we connect to layer 2 devices with this port fast it can create loops.
Configuration Command is
Switch(config)#interface fastethernet 0/1
Switch(config)#spanning-tree portfast
We Can Change the Root Bridge to the following command
there are two methods we can change the Root bridge
(1) Switch(config)#spanning-tree vlan 1 root primary
(2) Switch(config)#spanning-tree vlan 1 priority 4096
What is BPDU Guard?
BPDU:- Stand for Bridge Protocol Data Unit
If we configure port fast and after that the connecting layer 2 devices it can create loops but at this time we use BPDU Guard.
Configuration command is
Switch(config)#interface f0/2
Switch(config-if)#spanning-tree bpduguard enable
Switch(config-if)#exit
That for reading my tutorials...
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