CCNP Learning Note 14-Exchange Part---STP

STP Classification

Ieee	CISCO
802.1D STP Convergence 30-50s	PVST (ISL only); pvst+ (ISL & 802.1Q)
802.1W rapid-stp convergence within 1s	Rapid-pvst
802.1s MST	Mist/mst

802.1D stp===========pvst+ (ISL & 802.1Q)

Slow convergence and slow convergence

Switch-based VLAN-based

(redundant link is cut off, anti-ring simultaneously causes two links) (Configure different VLANs to go different links, anti-ring and not wasted)

-the difference between 802.1W RAPID-STP and Rapid-pvst is based on switch and VLAN-based

When the number of switch VLANs is huge, the VLAN-based spanning tree will increase correspondingly, and it will occupy a lot of switch resources when updating BPDUs (2s refresh).

MST is the partitioning of multiple VLANs into one instance, one for one tree, and the other to prevent loops while reducing the update BPDUs

BPDUs

Two kinds of 1, configuring BPDUs

2,TCN topology changes when used

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Protocol ID: reserved, always 0

version: 802.1d=0; 802.1w; 802.1s

message type: Mate version =0;TCN = 80. TCN messages are only here at the end, flag fields are for configuration messages

flag : 802.1d first and last two digits using FLAG

Root ID: rooted identity

Cost Path: The overhead used to determine which port of the block

Bridge ID: uniquely identifies a switch that is used to elect the root

Port ID: A port that uniquely identifies a switch

Message Age:

Max age:20s Refresh

Hello time:2s Refresh

forward delay: 15s

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STP Four processes

1, select the root mouth (the entire network selected one)

2, select the root port (select from all non-follow bridges, one per station)

3, select the specified port (one for each link)

4,blok the rest of the mouth

Root Bridge election:

Based on bridge ID (preferably small)

Bride Priority 2byte

MAC Address 5byte

Cisco Bridge ID

Bridge Priority 4bit Range 0-15 default =8

Extend SystemID 12bit differentiate VLAN

48bit MAC

The above structure priority is variable but the VLAN number can not be changed, so the whole is increased by 4,096 times times 2~12=4096, because bride the default = 8, all of the default =32768

0 0

1 4097

. .

8 32768

the actual project will not allow the device to elect their own roots, are set up artificially

Global: Spanning-tree VLAN 1 Root primary set this switch as the root

Global: Spanning-tree VLAN 1 root secondary Set this switch as the backup root

Global: Spanning-tree VLAN 1 primary xx=4096 multiple set priority

election root port:

1, the minimum root bridge ID (root ID, also a bride ID)

2, to the bottom of the root bridge cost

3, the smallest sender Brideid

4, the smallest sender Portid

5, the smallest receiver of the Portid

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CCNP Learning Note 14-Exchange Part---STP