1 Enterprise Lan Switching Cisco Ccna 200 125 200 105 m1 Slides [PDF]

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Enterprise LAN Switching for Cisco CCNA 200-125/200-105 SPANNING TREE PROTOCOL (STP)

Ross Bagurdes NETWORK ENGINEER

@bagurdes

Module Goals The need for STP STP operation STP demonstration

Broadcast Messages

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Broadcast Storm!

Spanning Tree Protocol Shuts Down Redundancy

X

Introducing Spanning Tree Protocol (STP)

Spanning Tree Protocol Shuts Down Redundancy

X

Spanning Tree Protocol

X

X

?

X

X X

X

Spanning Tree Protocol Operation 1. Select Root Bridge 2. Select “best” path to Root Bridge 3. Select port to block on non-Root Bridge

Bridge - A switch - A device that converts media from one type to another i.e. A wireless Ethernet to wired Ethernet bridge

Select the Root Bridge

Bridge Protocol Data Units (BPDU) A message used in STP to communicate: • • • • •

Root Bridge ID Cost to Root Bridge Senders Bridge ID Port ID STP timers

Select the Root Bridge

Select the Root Bridge Bridge ID

Priority

Switch MAC Address

32,769

0015.27A4.FD36

Bridge ID

Priority

VLAN ID Priority 1000000000000001

32,769 12 Bits

4 bits

Switch MAC Address

0015.27A4.FD36

Bridge ID

Priority

Priority

VLAN ID

32,769 12 Bits

4 bits

1000000000000001

Switch MAC Address

0015.27A4.FD36

Bridge ID

Priority

Switch MAC Address

32,769

0015.27A4.FD36

1000000000000001 Priority

VLAN ID

4 bits

12 Bits

VLAN 1 - Bridge Priority VLAN 1 Priority Options 0000000000000001

1

1000000000000001

32,769

0001000000000001

4,097

1001000000000001

36,865

0010000000000001

8,193

1010000000000001

40,961

0011000000000001

12,289

1011000000000001

45,057

0100000000000001

16,385

1100000000000001

49,153

0101000000000001

20,481

1101000000000001

53,249

0110000000000001

24,577

1110000000000001

57,345

0111000000000001

28,673

1111000000000001

61,441

VLAN 175 - Bridge Priority VLAN 175 Priority Options 0000000010101111

175

1000000010101111

32,943

0001000010101111

4,271

1001000010101111

37,039

0010000010101111

8,367

1010000010101111

41,135

0011000010101111

12,463

1011000010101111

45,231

0100000010101111

16,559

1100000010101111

49,327

0101000010101111

20,655

1101000010101111

53,423

0110000010101111

24,751

1110000010101111

57,519

0111000010101111

28,847

1111000010101111

61,615

Priority = Priority + VLAN ID

1000000000000001 Priority

VLAN ID

4 bits

12 Bits

Bridge ID

Priority

Switch MAC Address

32,769

0015.27A4.FD36

1000000000000001 Priority

VLAN ID

4 bits

12 Bits

Select the Root Bridge Bridge ID Priority

Switch MAC Address

Priority

Switch MAC Address

32,769

0015.27A4.FD36

32,769

6ADC.FC89.9974

Priority

Switch MAC Address

32,769

3175.AC8F.2121

Root Bridge Switch with the lowest Bridge ID.

Select the Root Bridge Bridge ID Priority

Switch MAC Address

Priority

Switch MAC Address

32,769

0015.27A4.FD36

32,769

6ADC.FC89.9974

Priority

Switch MAC Address

32,769

3175.AC8F.2121

Select the Root Bridge Root Bridge 32769:0015.27A4.FD36

32769:6ADC.FC89.9974 G0/1

A

G0/1 G0/3

G0/2

G0/3

G0/2

C 32769: 3175.AC8F.2121

B

Root Port Port on non-root bridge with the best cost to the root bridge.

STP Port Costs

Port Speed 10 Mbps 100 Mbps 1 Gbps 10 Gbps

Port Cost 100 19 4 2

Choose Root Ports Root Bridge 32769:0015.27A4.FD36

A

G0/3 4

Cost = 4

G0/1 4

G0/3 4

32769:6ADC.FC89.9974 G0/1 4

G0/2 4

C 32769: 3175.AC8F.2121

G0/2 4

B

Choose Root Ports Root Bridge 32769:0015.27A4.FD36

A

G0/3 4

G0/1 4

G0/3 4

32769:6ADC.FC89.9974 G0/1 4

G0/2 4

C 32769: 3175.AC8F.2121

G0/2 4

B

Cost = 4

Choose Root Ports Cost = 4 + 4 = 8

Root Bridge 32769:0015.27A4.FD36

A

G0/3 4

G0/1 4

G0/3 4

32769:6ADC.FC89.9974 G0/1 4

G0/2 4

C 32769: 3175.AC8F.2121

G0/2 4

B

Cost = 4

Choose Root Ports Root Bridge 32769:0015.27A4.FD36

A

G0/1 4

G0/3 4

Root Port

G0/3 4

32769:6ADC.FC89.9974 G0/1 4

G0/2 4

C 32769: 3175.AC8F.2121

G0/2 4

B

Choose Root Ports Root Bridge 32769:0015.27A4.FD36

A

G0/1

32769:6ADC.FC89.9974 Root Port

G0/1

G0/3

G0/2

Root Port

G0/3

G0/2

C 32769: 3175.AC8F.2121

B

Designated Port Port that receives and forwards frames.

Non-designated Port Port that drops incoming frames and does not send frames. *Receives and processes Bridge Protocol Data Units

Select Designated/Non-designated Ports Root Bridge 32769:0015.27A4.FD36

32769:6ADC.FC89.9974

DP

A

G0/1

DP

G0/3

Root Port

G0/1

DP

DP

X

G0/2

NDP

Root Port

G0/3

G0/2 DP

C 32769: 3175.AC8F.2121

B

Spanning Tree Protocol Process 1. Switch port link established (plug in cable)

X

2. Switch port begins in BLOCKING 3. Transition all ports to LISTENING state and send/process BPDUs (15 seconds) a) Transition non-designated ports to BLOCKING BLOCKING

4. Transition all designated ports to LEARNING state (15 seconds) 5. Transition all designated ports to FORWARDING state

Spanning Tree Protocol Protocol Process Process 1. Switch stops receiving BPDUs 2. Transition all ports to BLOCKING BLOCKING (20 seconds) LISTENING state 3. Transition all ports to LISTENING and send/process BPDUs (15 seconds) a) Transition non-designated ports to BLOCKING

4. Transition all designated ports to LEARNING state (15 seconds) 5. Transition all designated ports to FORWARDING state

Spanning Tree Protocol Process BLOCKING

20 seconds

LISTENING

15 seconds

LEARNING

15 seconds

FORWARDING

Demonstrating Spanning Tree Protocol

STP Demonstration 2960-1 32769:0cf5.a471.bd00 F0/1

2960-2 32769:2037.06d2.5500 F0/2

F0/2

F0/1

F0/1

F0/2

32769:0022.907f.3380 s3560

STP Demonstration 2960-1 32769:0cf5.a471.bd00 F0/1

2960-2 32769:2037.06d2.5500 F0/2

F0/2

F0/1

F0/1

F0/2 Root Bridge

32769:0022.907f.3380 s3560

STP Demonstration 2960-1 32769:0cf5.a471.bd00 F0/1 Root Port

2960-2 32769:2037.06d2.5500 F0/2

F0/2

F0/1

DP

DP F0/1

DP

F0/2

DP

Root Bridge 32769:0022.907f.3380 s3560

Root Port

STP Demonstration 2960-1 32769:0cf5.a471.bd00

DP F0/1 Root Port

F0/2

2960-2 32769:2037.06d2.5500

X

NDP

F0/2

F0/1

DP

DP F0/1

DP

F0/2

DP

Root Bridge 32769:0022.907f.3380 s3560

Root Port

Algorhyme I think that I shall never see A graph more lovely than a tree. A tree whose crucial property Is loop-free connectivity. A tree that must be sure to span So packets can reach every LAN First, the root must be selected. By ID, it’s elected. Least-cost paths from root are traced. In the tree, these paths are placed. A mesh is made by folks like me, Then bridges find a spanning tree.

-Radia Perlman

Summary The need for STP STP operation STP demonstration