Expl sw chapter_05_stp_part_i-rev2.

CCNA3-1 Chapter 5-1

Spanning Tree Protocol (STP)

Redundant Layer 2 TopologiesRedundant Layer 2 Topologies

CCNA3-2 Chapter 5-1

Redundant Layer 2 Topologies

• Ketersedian network infrastructure yang handal sangat dibutuhkan, khususnya pada bisnis yang memerlukan network yang memiliki tingkat link-down yang cukup kecil.

• Redundancy merupakan solusi untuk memastikan ketersediaan link network selalu ada.

• Layer 2 redundancy meningkatkan ketersediaan link netwok dengan menggunakan alternate network paths melalui penambahan device dan kabel pada network infrastruktur.

• Memiliki beberapa jalur data network dengan hanya allows for a single path untuk koneksi tanpa mengganggu konektivitas antar device dalam network.

• Spanning Tree Protocol (STP); logically blocks physical loops, dalam network dapat dengan cepat melakukan kalkulasi untuk menentukan port mana yang akan di block dalam network berbasis vlan.

CCNA3-3 Chapter 5-1

Redundancy

CCNA3-4 Chapter 5-1

Redundancy

Redundant paths create Redundant paths create loops loops in the network.in the network.

Redundant paths create Redundant paths create loops loops in the network.in the network.

How are they controlled?How are they controlled?Spanning Tree ProtocolSpanning Tree Protocol

How are they controlled?How are they controlled?Spanning Tree ProtocolSpanning Tree Protocol

CCNA3-5 Chapter 5-1

Redundancy

• Spanning Tree Protocol (STP) secara default berada dalam kondisi enabled pada semua switches.

• STP menempatkan salah satu ports switch dalam kondisi untuk melakukan forwarding state dan ports switch lainnya dalam kondisi blocking state.

ForwardForwardForwardForward

BlockedBlockedBlockedBlocked

CCNA3-6 Chapter 5-1

Issues with Redundancy

• Redundancy sangat penting dalam hierarchical design network.

• Ketika multiple paths terdapat diantara 2 devices dalam network dan STP telah di-disabled pada switches tersebut, maka Layer 2 loop akan terjadi.

• Jika STP di-enabled kan pada switches tersebut, atau dalam kondisi default, maka Layer 2 loop tidak akan terjadi.

• Dalam hierarchical design network infrastruktur, redundancy biasanya dilakukan pada distribution and core layers switch dengan cara menambah hardware dan alternative paths melalui hardware tambahan tersebut.

CCNA3-7 Chapter 5-1


• Ethernet frames tidak memiliki Time-To-Live (TTL) parameter seperti pada packets IP.

• Hal ini akan mengakibatkan, pengiriman ethernet frame tidak dapat dihentikan/not terminated dalam switched network, sehingga ethernet frame tersebut akan selalu berputar-putar dari switch ke switch tanpa tujuan yang jelas.

CCNA3-8 Chapter 5-1


• Kita harus ingat switches menggunakan Source MAC address untuk belajar dan mengetahui keberadaan suatu devices kemudian menyimpan information tersebut kedalam MAC address Tables.

• Switches akan melakukan flooding frames untuk mencari unknown destinations sampai mereka mempelajari dan mendapatkan informasi mengenai MAC addresses dari devices yang dimaksud.

CCNA3-9 Chapter 5-1


• Sebagai tambahan, multicasts dan broadcasts juga akan flooded ke semua port kecuali receiving port. (Multicasts will not be flooded if the switch has been specifically configured to handle multicasts.)

• http://www.cisco.com/en/US/docs/switches/lan/catalyst2960/software/release/12.2_25_see/configuration/guide/swigmp.html

CCNA3-10 Chapter 5-1


PC1 sends a PC1 sends a broadcast.broadcast.


S2 receives the S2 receives the frame and updates frame and updates

the MAC table.the MAC table.

S2 receives the S2 receives the frame and updates frame and updates

the MAC table.the MAC table.

S2 floods the S2 floods the broadcast out all broadcast out all ports except the ports except the receiving port.receiving port.

S2 floods the S2 floods the broadcast out all broadcast out all ports except the ports except the receiving port.receiving port.

S3 and S1 update S3 and S1 update their MAC tablestheir MAC tables

S3 and S1 update S3 and S1 update their MAC tablestheir MAC tables

S3 and S1 now S3 and S1 now flood the broadcast.flood the broadcast.

S3 and S1 now S3 and S1 now flood the broadcast.flood the broadcast.

S3 and S1 update S3 and S1 update their MAC tables their MAC tables with the wrong with the wrong

informationinformation

S3 and S1 update S3 and S1 update their MAC tables their MAC tables with the wrong with the wrong

informationinformation

S3 and S1 forward S3 and S1 forward the broadcast back the broadcast back

to S2.to S2.

S3 and S1 forward S3 and S1 forward the broadcast back the broadcast back

to S2.to S2.

S2 updates its S2 updates its MAC table with the MAC table with the wrong informationwrong information

S2 updates its S2 updates its MAC table with the MAC table with the wrong informationwrong information

S2 S2 floodsfloods the the broadcast againbroadcast again

S2 S2 floodsfloods the the broadcast againbroadcast againS3 and S1 update their S3 and S1 update their MAC tables again with MAC tables again with the the wrong informationwrong information

S3 and S1 update their S3 and S1 update their MAC tables again with MAC tables again with the the wrong informationwrong information



• Broadcast Storms:

PC1 sends a PC1 sends a broadcastbroadcast


No STPNo STP so a so aloop is createdloop is createdNo STPNo STP so a so a

loop is createdloop is createdPC4 sends a PC4 sends a

broadcastbroadcastPC4 sends a PC4 sends a

broadcastbroadcastAnother loopAnother loopAnother loopAnother loopPC3 sends a broadcast and PC3 sends a broadcast and creates yet another loopcreates yet another loop

PC3 sends a broadcast and PC3 sends a broadcast and creates yet another loopcreates yet another loop



Because of the high Because of the high level of traffic, it level of traffic, it

cannot be processed.cannot be processed.

Because of the high Because of the high level of traffic, it level of traffic, it

cannot be processed.cannot be processed.

In fact, the entire network can In fact, the entire network can no longer process new traffic no longer process new traffic

and comes to a screeching halt.and comes to a screeching halt.

In fact, the entire network can In fact, the entire network can no longer process new traffic no longer process new traffic

and comes to a screeching halt.and comes to a screeching halt.



• Duplicate Unicast Frames:

PC1 sends a PC1 sends a unicastunicast frame frame

to PC4to PC4

PC1 sends a PC1 sends a unicastunicast frame frame

to PC4to PC4

S2 has no entry for S2 has no entry for PC4 so the frame PC4 so the frame is flooded out the is flooded out the remaining portsremaining ports

S2 has no entry for S2 has no entry for PC4 so the frame PC4 so the frame is flooded out the is flooded out the remaining portsremaining ports

Both S3 and S1 have Both S3 and S1 have entries for PC4 so the entries for PC4 so the

frame is forwardedframe is forwarded

Both S3 and S1 have Both S3 and S1 have entries for PC4 so the entries for PC4 so the

frame is forwardedframe is forwarded

S1 also forwards S1 also forwards the frame it the frame it

received from S3received from S3

S1 also forwards S1 also forwards the frame it the frame it

received from S3received from S3

End result….End result….PC4 receives two copies of the same PC4 receives two copies of the same frame. One from S1 and one from S3.frame. One from S1 and one from S3.

End result….End result….PC4 receives two copies of the same PC4 receives two copies of the same frame. One from S1 and one from S3.frame. One from S1 and one from S3.


Real-World Redundancy Issues

• Loops in the Wiring Closet:• Error biasanya disebabkan masalah dalam pengkabelan.


Real-World Redundancy Issues

• Loops in Cubicles:• Beberapa user memiliki personal switch atau hub.

Affects all of the Affects all of the traffic on S1traffic on S1

Affects all of the Affects all of the traffic on S1traffic on S1


Spanning Tree Protocol (STP)

Introduction to STPIntroduction to STP


Spanning-Tree Algorithm (STA)

• STP Topology – Avoiding a loop (menghindari terjadinya looping):

STP is in use and S3 STP is in use and S3 has placed port F0/2 has placed port F0/2 in in blocking stateblocking state to to

avoid a loop.avoid a loop.

STP is in use and S3 STP is in use and S3 has placed port F0/2 has placed port F0/2 in in blocking stateblocking state to to

avoid a loop.avoid a loop.



S2 forwards the S2 forwards the broadcast – broadcast – but but

not to S3not to S3..

S2 forwards the S2 forwards the broadcast – broadcast – but but

not to S3not to S3..

S1 forwards the S1 forwards the broadcast.broadcast.


Because F0/2 is in Because F0/2 is in blocking stateblocking state, the , the broadcast is not broadcast is not

forwardedforwarded back to back to S2. – NO LOOP!S2. – NO LOOP!

Because F0/2 is in Because F0/2 is in blocking stateblocking state, the , the broadcast is not broadcast is not

forwardedforwarded back to back to S2. – NO LOOP!S2. – NO LOOP!



• STP Topology – Network Failure (Kegagalan Network):

Trunk 1 Trunk 1 FailureFailureTrunk 1 Trunk 1 FailureFailure

S3 port S3 port activatedactivatedS3 port S3 port

activatedactivated

PC1 Sends a PC1 Sends a broadcast.broadcast.

PC1 Sends a PC1 Sends a broadcast.broadcast.



S3 and S1 forward S3 and S1 forward the broadcast.the broadcast.

S3 and S1 forward S3 and S1 forward the broadcast.the broadcast.

Trunk 1 comes Trunk 1 comes back up.back up.

Trunk 1 comes Trunk 1 comes back up.back up.

S3 port back to S3 port back to blocking modeblocking mode..S3 port back to S3 port back to blocking modeblocking mode..



• Terminology:• Root Bridge:

• Switch yang digunakan sebagai reference point untuk semua calculations.

• Root Ports:• Port Switch terdekat ke root bridge.

• Designated Port:• Semua port yang bukan root (non-root ports) yang

diberi izin untuk mem-forward traffic didalam network.• Non-designated Ports:

• Semua ports yang di-configured dalam kondisi mem-blocking untuk menghindari terjadinya loops.



• STP menggunakan Spanning Tree Algorithm (STA) untuk menentukan port switch yang mana dalam network yang akan di configurasi untuk melakukan blocking agar tidak terjadi loops.

• STP memastikan hanya ada 1 logical path diantara semua destinations yang ada dalam network dengan cara memblocking redundant path untuk mencegah terjadinya loops.

• Melalui proses election/pemilihan, algorithma akan memilih single switch sebagai root bridge dan menggunakannya sebagai reference point untuk semua calculations.

• Election process di controlled menggunakan Bridge-ID (BID).

BridgePriority

MACMACAddressAddress

2222 6666


Root Bridge

• Election Process:• Pada semua switches yang berpartisipasi dalam broadcast domain.• Setelah switch selesai melakukan boots, switch akan mengirim keluar

Frame Bridge Protocol Data Units (BPDU), yang berisi Bridge ID dan Root ID dari switch, setiap 2 seconds.

• Bagaimana cara mengidentifikasikan root ID dari root bridge (switch referensi point/switch root bridge) di network..?

Menentukan Root Bridge. The Root Bridge of the spanning tree is the bridge with

the smallest (lowest) Bridge ID.

Setiap Bridge memiliki unique identifier (ID) and priority number yang bisa di konfigurasi; dengan kata lain; Bridge ID contains both numbers.

To compare 2 Bridge IDs, the priority is compared first. If two bridges have equal priority, then the MAC

addresses are compared.


Root Bridge

Lanjutan : Select a root bridge. For example:Misalnya :Switch A memiliki (MAC=0200.0000.11110200.0000.1111) dan Switch B memiliki (MAC=0200.0000.22220200.0000.2222), Kedua Switch tersebut memiliki nilai priority yang sama, yaitu 10 (default), maka untuk memilih switch yang akan menjadi root bridge kita bandingkan mac-addressnya, dan yang memiliki mac-address terkecil akan menjadi root bridge;

Maka : Switch A will be selected as the Root Bridge.

If the network administrator would like switch B to become the root bridge, they must set its priority to be less than 10 (<10).

• Secara default, Root ID sama dengan local Bridge ID pada semua switch di dalam network. • Dengan kata lain, semua switch menganggap dirinya sebagai

root bridge ketika pertama kali switch selesai melakukan boots.


Root Bridge

• Switches mem-forward frame BPDU-nya, switches di dalam broadcast domain read the root ID information dari BPDU frame.

• Jika root ID dari BPDU yang diterima lower than the root ID switch penerima, switch penerima akan meng-updates root ID tersebut dengan mengidentifikasi switch terdekat tersebut sebagai root bridge.

• Selanjutnya switch akan mem-forwards new BPDU frames with the lower root ID tadi ke switches adjacent/tetangga lainnya.

• Akhirnya, switch yang memiliki lowest BID (Bridge ID terkecil) paling terakhir akan dikenal sebagai Root Bridge untuk spanning-tree instance.


Best Path

• Setelah Root Bridge sudah dipilih, maka STA memulai process pemilihan best paths ke Root Bridge dari semua destinations yang ada didalam broadcast domain.

• Path information ditentukan melalui summing up the individual port costs disepanjang path (egress) dari destination ke root bridge.

• Default/Standart Port Costs yang ditetapkan oleh IEEE dan didefenisikan berdasarkan kecepatan dari port adalah sebagai berikut:

Link SpeedLink Speed CostCost

10Gbps 2

1Gbps 4

100Mbps 19

10Mbps 100


Best Path

• You are not restricted to the defaults.• Cost of a path can be manually configured to specific path

agar diterima oleh STA sebagai pilihan best path.• Path Cost adalah the sum of all the egress port costs to the

root bridge.• Path dengan lowest cost (cost terkecil) akan menjadi Perferred

Path dan yang lainnya akan di blocked

switch(config)#interface fa0/1switch(config-if)#spanning-tree cost [value]switch(config-if)#end

Value can be between: 1 ….. 200,000,000

• The ‘no’ form of the following command will return the cost to its default value.


Best Path

• Verifying the port and path cost (to the root bridge).

Port CostPort CostPort CostPort Cost

Path CostPath CostPath CostPath Cost


BPDU Process

• Root Bridge Election Process:

S3 believes S2 is the root bridge.S3 believes S2 is the root bridge.S1 still thinks it is the root bridge.S1 still thinks it is the root bridge.S3 believes S2 is the root bridge.S3 believes S2 is the root bridge.S1 still thinks it is the root bridge.S1 still thinks it is the root bridge.


BPDU Process


S2 and S1 both think that theyS2 and S1 both think that theyare the root bridge.are the root bridge.

S2 and S1 both think that theyS2 and S1 both think that theyare the root bridge.are the root bridge.


BPDU Process


S3 recognizes S1 as the root.S3 recognizes S1 as the root.S2 recognizes S1 as the root.S2 recognizes S1 as the root.S3 recognizes S1 as the root.S3 recognizes S1 as the root.S2 recognizes S1 as the root.S2 recognizes S1 as the root.


BPDU Process


If the root bridge fails, the election If the root bridge fails, the election process begins again.process begins again.

If the root bridge fails, the election If the root bridge fails, the election process begins again.process begins again.


Bridge ID

Early STP implementation – no VLANs.Early STP implementation – no VLANs.Early STP implementation – no VLANs.Early STP implementation – no VLANs.

Changed to include VLAN ID.Changed to include VLAN ID.Changed to include VLAN ID.Changed to include VLAN ID.

That means that there is That means that there is a separate a separate instance of STPinstance of STP for each VLAN. for each VLAN.

That means that there is That means that there is a separate a separate instance of STPinstance of STP for each VLAN. for each VLAN.


Bridge ID


Bridge ID

• Bridge Priority:• Customizable value yang dapat dipergunakan untuk

mempengaruhi/merubah switch untuk menjadi root bridge.

• Switch yang memiliki nilai lowest priority (priority terkecil), berarti switch tersebut memiliki BID terkecil, dan akan menjadi root bridge.


Bridge ID

• Bridge Priority:• Penambahan VLAN ID akan mengurangi bits yang

tersedia untuk bridge priority (dari 16bits menjadi 4bits).• Oleh karena itu, nilai bridge priority ditetapkan dengan

kelipatan 4096.• Nilai priority akan ditambahkan ke extended system value

(VLAN ID) sebagai identifikasi dari Priority dan VLAN dalam BPDU frame.

++++


Bridge ID

• Bridge Priority:• For example, pada sebuah switch:

• The default bridge priority = 32,769.

= (4096 * 8) + VLAN 1 ( native VLAN)• If I assign bridge priority = 24,576 for VLAN 1 = (24,576) + VLAN 1 , the bridge priority becomes 24,577

• Maka switch ini akan menjadi root bridge.

++++


Bridge ID

• Bridge Priority:

Default Priority:Default Priority:Election based on Election based on

MAC AddressMAC Address

Default Priority:Default Priority:Election based on Election based on

MAC AddressMAC Address


Bridge ID

• Bridge Priority:

Modified Priority:Modified Priority:Election based on Election based on

priority.priority.

Modified Priority:Modified Priority:Election based on Election based on

priority.priority.


Configure and Verify the Bridge ID

• Two Methods to configure the Bridge ID:• Metode 1: Menetapkan bahwa switch memiliki Menetapkan bahwa switch memiliki

nilai prioritas terendahnilai prioritas terendahMenetapkan bahwa switch memiliki Menetapkan bahwa switch memiliki

nilai prioritas terendahnilai prioritas terendah

Menetapkan switch akan menjadi root bridge jika Menetapkan switch akan menjadi root bridge jika primary switch fails.primary switch fails.

Menetapkan switch akan menjadi root bridge jika Menetapkan switch akan menjadi root bridge jika primary switch fails.primary switch fails.



• Two Methods to configure the Bridge ID:• Metode 2:

VLAN ID NumberVLAN ID NumberVLAN ID NumberVLAN ID Number Priority valuePriority valuePriority valuePriority value


Port Roles

• Root bridge akan dipilih oleh spanning-tree menjadi link utama.• Location dari root bridge dalam network topology akan menentukan

bagaimana port roles dikalkulasikan.• Root Port (exists on non-root bridges):

• Port switch yang best-path/terbaik untuk mem-forward traffic ke root bridge.

• Hanya ada 1 root port per switch• Designated Port (forward data frames):

• Port switch yang me-receives & mem-forwards frames ke arah root bridge tujuan. Hanya ada 1 designated port per segment/koneksi.

• Untuk switch root bridges, semua ports-nya adalah designated ports

• Non-designated Port:• Port switch yang diblocked oleh spanning tree, dan tidak akan

mem-forwarding data frames.


Port Roles

• STA akan menentukan jenis dari port dari setiap port yang terdapat pada switch.

• Untuk menentukan root port pada switch, yaitu:• Switch akan membandingkan path costs pada semua

port switch yang berpartisipasi dalam spanning tree.• Jika terdapat 2 port switch yang memiliki path cost yang

sama menuju root bridge, maka:• Switch akan menggunakan customizable port priority

value, atau lowest port ID.• Port ID adalah nomor dari connected port/nomor

port.


Port Roles – Root Port

• For Example: Default Port Priority = 128Default Port Priority = 128Default Port Priority = 128Default Port Priority = 128

F0/1 Priority = 128,1F0/1 Priority = 128,1F0/1 Priority = 128,1F0/1 Priority = 128,1



• You can specify the root port:• Configure Port Priority:

SW3(config)#interface fa0/23

SW3(config-if)#spanning-tree vlan 1 port-priority 32

• Priority values 0 - 240, in increments of 16. • Default port priority value is 128.• The lower the port priority value, the higher the

priority.



• Verifying the Port Priority:


Part II

(next session)

Expl sw chapter_05_stp_part_i-rev2.

Technology

Transcript of Expl sw chapter_05_stp_part_i-rev2.