книги / Сети передачи данных

Убедимся в правильности приведенных на рис. 1.5 статусе и состоянии портов коммутаторов согласно разд. 1 пособия, исполь-

зуя вывод команд Show Spanning-Tree VLAN 1 и Show SpanningTree Detail. Состояние коммутаторов будет выглядеть так:

Sw1:

sw1.lab#show spanning-tree detail

VLAN0001 is executing the ieee compatible Spanning Tree protocol

Bridge Identifier has priority 32768, sysid 1, address 0019.3096.eb80

Configured hello time 2, max age 20, forward delay 15 We are the root of the spanning tree (здесь и далее цветом выделены важные элементы, к некоторым будут даны

пояснения)

Topology change flag not set, detected flag not set Number of topology changes 20 last change occurred

00:04:47 ago

Times: hold 1, topology change 35, notification 2 hello 2, max age 20, forward delay 15

Timers: hello 0, topology change 0, notification 0,

aging 300

* Этот коммутатор стал корневым (Root Bridge для

VLAN 1).

Port 1 (FastEthernet0/1) of VLAN0001 is forwarding Port path cost 19, Port priority 128, Port Identi-

fier 128.1.

Designated root has priority 32769, address 0019.3096.eb80

Designated bridge has priority 32769, address 0019.3096.eb80

Designated port id is 128.1, designated path cost 0 Timers: message age 0, forward delay 0, hold 0 Number of transitions to forwarding state: 5

Link type is point-to-point by default

BPDU: sent 627, received 1981

* Path Cost для этого порта = 19, Port Priority = = 128, PID = 128.1.

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Port 3 (FastEthernet0/3) of VLAN0001 is forwarding

Port path cost 19, Port priority 128, Port Identifier

128.3.

Designated root has priority 32769, address 0019.3096.eb80

Designated bridge has priority 32769, address 0019.3096.eb80

Designated port id is 128.3, designated path cost 0

Port 25 (GigabitEthernet0/1) of VLAN0001 is forwarding

Port path cost 4, Port priority 128, Port Identi-

fier 128.25.

Designated root has priority 32769, address 0019.3096.eb80

Designated bridge has priority 32769, address 0019.3096.eb80

Designated port id is 128.25, designated path cost 0 Timers: message age 0, forward delay 0, hold 0 Number of transitions to forwarding state: 3

Link type is point-to-point by default

BPDU: sent 169, received 2454

* Path Cost для этого порта = 4, Port Priority = = 128, PID = 128.25.

VLAN0001 is executing the ieee compatible Spanning Tree protocol

Bridge Identifier has priority 32768, sysid 1, address 001c.b1de.6000

Configured hello time 2, max age 20, forward delay 15

Current root has priority 32769, address 0019.3096.eb80

Root port is 26 (GigabitEthernet0/2), cost of root path is 4

Topology change flag not set, detected flag not set Number of topology changes 24 last change occurred

00:04:59 ago

from GigabitEthernet0/1

Times: hold 1, topology change 35, notification 2 hello 2, max age 20, forward delay 15

Timers: hello 0, topology change 0, notification 0,

aging 300

* Информация о том, что корневой Sw1, RPC = 4 от

Sw2 к Sw1.

Port 2 (FastEthernet0/2) of VLAN0001 is forwarding Port path cost 19, Port priority 128, Port Identi-

fier 128.2.

Designated root has priority 32769, address 0019.3096.eb80

Designated bridge has priority 32769, address 001c.b1de.6000

Designated port id is 128.2, designated path cost 4 Timers: message age 0, forward delay 0, hold 0 Number of transitions to forwarding state: 1

Link type is point-to-point by default

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BPDU: sent 396, received 0

Port 25 (GigabitEthernet0/1) of VLAN0001 is forwarding

Port path cost 4, Port priority 128, Port Identi-

fier 128.25.

Designated root has priority 32769, address 0019.3096.eb80

Designated bridge has priority 32769, address 001c.b1de.6000

Designated port id is 128.25, designated path cost 4 Timers: message age 0, forward delay 0, hold 0 Number of transitions to forwarding state: 1

Link type is point-to-point by default BPDU: sent 755, received 2008

Port 26 (GigabitEthernet0/2) of VLAN0001 is forwarding

Port path cost 4, Port priority 128, Port Identi-

fier 128.26.

Designated root has priority 32769, address 0019.3096.eb80

Designated bridge has priority 32769, address 0019.3096.eb80

sw3.lab#show spanning-tree detail

VLAN0001 is executing the ieee compatible Spanning Tree protocol

Bridge Identifier has priority 32768, sysid 1, address 04fe.7f2b.e680

Configured hello time 2, max age 20, forward delay 15 Current root has priority 32769, address

0019.3096.eb80

Root port is 26 (GigabitEthernet0/2), cost of root path is 12

Topology change flag not set, detected flag not set Number of topology changes 42 last change occurred

00:04:28 ago

Times: hold 1, topology change 35, notification 2 hello 2, max age 20, forward delay 15

Timers: hello 0, topology change 0, notification 0, aging 300

Port 1 (FastEthernet0/1) of VLAN0001 is alternate blocking

Port path cost 19, Port priority 128, Port Identifier 128.1.

Designated root has priority 32769, address 0019.3096.eb80

Designated bridge has priority 32769, address 0019.3096.eb80

Designated port id is 128.1, designated path cost 0 Timers: message age 1, forward delay 0, hold 0 Number of transitions to forwarding state: 4

Link type is point-to-point by default BPDU: sent 2488, received 933

Port 2 (FastEthernet0/2) of VLAN0001 is designated forwarding

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Port path cost 19, Port priority 128, Port Identifier 128.2.

Designated root has priority 32769, address 0019.3096.eb80

Designated bridge has priority 32769, address 04fe.7f2b.e680

Designated port id is 128.2, designated path cost 12 Timers: message age 0, forward delay 0, hold 0 Number of transitions to forwarding state: 1

Link type is point-to-point by default BPDU: sent 380, received 0

Port 3 (FastEthernet0/3) of VLAN0001 is alternate blocking

Port path cost 19, Port priority 128, Port Identifier 128.3.

Designated root has priority 32769, address 0019.3096.eb80

Designated bridge has priority 32769, address 0019.3096.eb80

Designated port id is 128.3, designated path cost 0 Timers: message age 2, forward delay 0, hold 0 Number of transitions to forwarding state: 3

Link type is point-to-point by default BPDU: sent 1149, received 170

Port 26 (GigabitEthernet0/2) of VLAN0001 is root forwarding

Port path cost 4, Port priority 128, Port Identifier 128.26.

Designated root has priority 32769, address 0019.3096.eb80

Designated bridge has priority 32769, address 04fe.7f86.7980

Designated port id is 128.26, designated path cost 8 Timers: message age 4, forward delay 0, hold 0 Number of transitions to forwarding state: 1

Link type is point-to-point by default BPDU: sent 993, received 1758

Sw3.lab#show spanning-tree vlan 1

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VLAN0001

Spanning tree enabled protocol ieee Root ID Priority 32769

Address 0019.3096.eb80 Cost 12

Port 26 (GigabitEthernet0/2)

Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Bridge ID Priority 32769 (priority 32768 sys-id-ext 1) Address 04fe.7f2b.e680

Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Aging Time 300

sw4.lab#show spanning-tree detail

VLAN0001 is executing the ieee compatible Spanning Tree protocol

Bridge Identifier has priority 32768, sysid 1, address 04fe.7f86.7980

Configured hello time 2, max age 20, forward delay 15

Current root has priority 32769, address

0019.3096.eb80

Root port is 25 (GigabitEthernet0/1), cost of root

path is 8

Topology change flag not set, detected flag not set Number of topology changes 18 last change occurred

00:04:12 ago

Port path cost 4, Port priority 128, Port Identifier 128.25.

Designated root has priority 32769, address 0019.3096.eb80

Designated bridge has priority 32769, address 001c.b1de.6000

Designated port id is 128.25, designated path cost 4 Timers: message age 3, forward delay 0, hold 0 Number of transitions to forwarding state: 1

Link type is point-to-point by default BPDU: sent 2008, received 730

Port 26 (GigabitEthernet0/2) of VLAN0001 is designated forwarding

Port path cost 4, Port priority 128, Port Identifier 128.26.

Designated root has priority 32769, address 0019.3096.eb80

Designated bridge has priority 32769, address 04fe.7f86.7980

Designated port id is 128.26, designated path cost 8 Timers: message age 0, forward delay 0, hold 0 Number of transitions to forwarding state: 1

Link type is point-to-point by default BPDU: sent 1750, received 993

sw4.lab#show spanning-tree vlan 1

VLAN0001

Spanning tree enabled protocol ieee

Root ID Priority 32769

Address 0019.3096.eb80

Cost 8

Port 25 (GigabitEthernet0/1)

Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Bridge ID Priority 32769 (priority 32768 sys-id-ext 1) Address 04fe.7f86.7980

Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Aging Time 300

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1.2.2. Изменение места положения корня

Изменим место положения корневого коммутатора путем уменьшения поля приоритета в ВID. Например, чтобы Root Bridge стал Sw2 (рис. 1.12), изменим его приоритет в BID.

Рис. 1.12. Смена корневого моста

Настройте приоритет 4096 на Sw2:

Sw2:

sw2.lab#configure terminal

sw2.lab(config)# spanning-tree vlan 1 priority 4096

В результате вывод команды Show Spanning-Tree VLAN 1 на коммутаторах:

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Sw1:

sw1.lab#show spanning-tree vlan 1

VLAN0001

Spanning tree enabled protocol ieee

Root ID Priority 4097

Address 001c.b1de.6000

Cost 4

Port 25 (GigabitEthernet0/1)

Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Bridge ID Priority 32769 (priority 32768 sys-id-ext 1) Address 0019.3096.eb80

Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Aging Time 15

*Информация о том, какой сейчас новый Root Bridge.

Sw2:

sw2.lab#show spanning-tree vlan 1

18w1d: %SYS-5-CONFIG_I: Configured from console by console

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