STP Study Guide All - Revision history

West0476: /* PortFast */

2012-02-06T15:31:26Z

PortFast

← Older revision		Revision as of 15:31, 6 February 2012
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	='''PortFast'''=		='''PortFast'''=

	Spanning Tree Portfast causes an interface configured as a layer 2 access port to enter the forwarding state immediately. Conf t int fa 0/1 spanning-tree portfast		Spanning Tree Portfast causes an interface configured as a layer 2 access port to enter the forwarding state immediately.

			Conf t int fa 0/1 spanning-tree portfast

	confirm with show spanning-tree interface Fastethernet 0/1.		confirm with show spanning-tree interface Fastethernet 0/1.

	Config the Basic Parameters of PVRST+ conf t spanning-tree mode rapid-pvst spanning-tree vlan 2 root primary spanning tree- vlan 3 root secondary		Config the Basic Parameters of PVRST+ conf t spanning-tree mode rapid-pvst spanning-tree vlan 2 root primary spanning tree- vlan 3 root secondary

West0476: /* Only four high-order bits of the 16 bit bridge priority field carry actual priority */

2012-02-06T15:30:56Z

Only four high-order bits of the 16 bit bridge priority field carry actual priority

← Older revision		Revision as of 15:30, 6 February 2012
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	MST		MST

	~~PortFast~~

	~~Spanning Tree Portfast causes an interface configured as a layer 2 access port to enter the forwarding state immediately.~~

	~~Conf t~~

	~~int fa 0/1~~

	~~spanning-tree portfast~~

	~~confirm with show spanning-tree interface Fastethernet 0/1.~~

	='''Config the Basic Parameters of PVRST+'''=		='''Config the Basic Parameters of PVRST+'''=

West0476: /* Selects the Root Port on All Non-root Bridges */

2012-02-06T15:29:50Z

Selects the Root Port on All Non-root Bridges

← Older revision		Revision as of 15:29, 6 February 2012
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	• The protocol establishes one root port on each nonroot bridge.		• The protocol establishes one root port on each nonroot bridge.

	• The root port is the lowest-cost path from the nonroot bridge to the root bridge		• The root port is the lowest-cost path from the nonroot bridge to the root bridge

West0476: /* Bridge Identifier for PVRST+ */

2012-02-06T15:28:23Z

Bridge Identifier for PVRST+

← Older revision		Revision as of 15:28, 6 February 2012
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	Bridge Priority A 4-bit field still used to carry bridge priority		Bridge Priority A 4-bit field still used to carry bridge priority

	Extended System ID		Extended System ID

	Mac Address		Mac Address
	Only four high-order bits of the 16 bit bridge priority field carry actual priority
			='''Only four high-order bits of the 16 bit bridge priority field carry actual priority'''=

	Cisco STP Default Config		Cisco STP Default Config

	PVST+		PVST+

	PVRST+		PVRST+

	MST		MST

	PortFast		PortFast

	Spanning Tree Portfast causes an interface configured as a layer 2 access port to enter the forwarding state immediately.		Spanning Tree Portfast causes an interface configured as a layer 2 access port to enter the forwarding state immediately.

	Conf t		Conf t

	int fa 0/1		int fa 0/1

	spanning-tree portfast		spanning-tree portfast

	confirm with show spanning-tree interface Fastethernet 0/1.		confirm with show spanning-tree interface Fastethernet 0/1.
	Config the Basic Parameters of PVRST+
			='''Config the Basic Parameters of PVRST+'''=

	conf t		conf t

	spanning-tree mode rapid-pvst		spanning-tree mode rapid-pvst

	spanning-tree vlan 2 root primary		spanning-tree vlan 2 root primary

	spanning tree- vlan 3 root secondary		spanning tree- vlan 3 root secondary

West0476: /* RSTP bridge port roles: */

2012-02-06T15:26:10Z

RSTP bridge port roles:

← Older revision		Revision as of 15:26, 6 February 2012
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	Root - A forwarding port that is the best port from Non root-bridge to Root bridge		Root - A forwarding port that is the best port from Non root-bridge to Root bridge

	Designated - A forwarding port for every LAN segment		Designated - A forwarding port for every LAN segment

	Alternate - An alternate path to the root bridge. This path is different than using the root port.		Alternate - An alternate path to the root bridge. This path is different than using the root port.

	Backup - A backup/redundant path to a segment where another bridge port already connects.		Backup - A backup/redundant path to a segment where another bridge port already connects.

	Disabled - Not strictly part of STP, a network administrator can manually disable a port		Disabled - Not strictly part of STP, a network administrator can manually disable a port

West0476: /* There are Five Port States */

2012-02-06T15:25:49Z

There are Five Port States

← Older revision		Revision as of 15:25, 6 February 2012
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	• Blocking		• Blocking

	• Listening		• Listening

	• Learning		• Learning

	• Forwarding		• Forwarding

	• Disabled		• Disabled

West0476: /* There are four roles of ports under STP */

2012-02-06T15:25:37Z

There are four roles of ports under STP

← Older revision		Revision as of 15:25, 6 February 2012
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	1) Root		1) Root

	2) Designated		2) Designated

	3) Non-Designated		3) Non-Designated

	4) Disabled		4) Disabled

West0476 at 15:25, 6 February 2012

2012-02-06T15:25:20Z

← Older revision		Revision as of 15:25, 6 February 2012
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	='''Selects the Root Port on All Non-root Bridges'''=		='''Selects the Root Port on All Non-root Bridges'''=

	• The protocol establishes one root port on each nonroot bridge.		• The protocol establishes one root port on each nonroot bridge.
	• The root port is the lowest-cost path from the nonroot bridge to the root bridge		• The root port is the lowest-cost path from the nonroot bridge to the root bridge

	='''Selects Designated Port on Each Segment		='''Selects Designated Port on Each Segment'''=
	'''= • On each segment, STP establishes one designated port on the bridge that has the lowest path cost to the root bridge
			• On each segment, STP establishes one designated port on the bridge that has the lowest path cost to the root bridge
	• The switch primarily chooses a designated port as the least-cost path to the root bridge		• The switch primarily chooses a designated port as the least-cost path to the root bridge
	• In the event of a tie, the bridge ID acts as the tiebreaker		• In the event of a tie, the bridge ID acts as the tiebreaker
	• Port Roles		• Port Roles

	='''There are four roles of ports under STP		='''There are four roles of ports under STP'''=
	'''= 1) Root
			1) Root
	2) Designated		2) Designated
	3) Non-Designated		3) Non-Designated
	4) Disabled		4) Disabled

	='''There are Five Port States		='''There are Five Port States'''=
	'''= • Blocking
			• Blocking
	• Listening		• Listening
	• Learning		• Learning
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	• Disabled		• Disabled

	='''RSTP		='''RSTP'''=
	'''=~~A variation of Spanning Tree Protocol (STP) designed to ensures a topology that doesn’t have loops.~~

	='''IEEE introduced Rapid Spanning Tree Protocol (RSTP) as 802.1w		A variation of Spanning Tree Protocol (STP) designed to ensures a topology that doesn’t have loops.
	'''= Detection of root switch failure is done in 3 hello times
			='''IEEE introduced Rapid Spanning Tree Protocol (RSTP) as 802.1w'''=

			Detection of root switch failure is done in 3 hello times
	STP can take 30 to 50 seconds to respond to a topology change, RSTP is typically able to respond to changes within 3 × Hello times *(default: 3 times 2 seconds) or within a few milliseconds of a physical link failure		STP can take 30 to 50 seconds to respond to a topology change, RSTP is typically able to respond to changes within 3 × Hello times *(default: 3 times 2 seconds) or within a few milliseconds of a physical link failure
	RSTP maintains backup details regarding the discarding status of ports.		RSTP maintains backup details regarding the discarding status of ports.

	='''RSTP bridge port roles:		='''RSTP bridge port roles:'''=
	'''= Root - A forwarding port that is the best port from Non root-bridge to Root bridge
			Root - A forwarding port that is the best port from Non root-bridge to Root bridge
	Designated - A forwarding port for every LAN segment		Designated - A forwarding port for every LAN segment
	Alternate - An alternate path to the root bridge. This path is different than using the root port.		Alternate - An alternate path to the root bridge. This path is different than using the root port.
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	Disabled - Not strictly part of STP, a network administrator can manually disable a port		Disabled - Not strictly part of STP, a network administrator can manually disable a port

	='''RSTP Topology Change Mechanism		='''RSTP Topology Change Mechanism'''=
	'''=When an RSTP bridge detects a topology change it performs the following actions.
			When an RSTP bridge detects a topology change it performs the following actions.
	The RSTP Bridge starts the TC while time with a value equal to twice the hello time for all its non-edge designated ports and its root, port if necessary. The TC While time is the interval during which the RSTP Bridge actively informs the rest of the bridges in the network of a topology. It then flushes the MAC addresses associated with all non-edge ports. And as long as the TC While timer is running the BPDUs will be sent out of the port will have the TC bit set.		The RSTP Bridge starts the TC while time with a value equal to twice the hello time for all its non-edge designated ports and its root, port if necessary. The TC While time is the interval during which the RSTP Bridge actively informs the rest of the bridges in the network of a topology. It then flushes the MAC addresses associated with all non-edge ports. And as long as the TC While timer is running the BPDUs will be sent out of the port will have the TC bit set.

	='''Bridge Identifier for PVRST+		='''Bridge Identifier for PVRST+'''=
	'''= Bridge Priority A 4-bit field still used to carry bridge priority
			Bridge Priority A 4-bit field still used to carry bridge priority
	Extended System ID		Extended System ID
	Mac Address		Mac Address
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	='''PortFast'''=		='''PortFast'''=

	Spanning Tree Portfast causes an interface configured as a layer 2 access port to enter the forwarding state immediately. Conf t int fa 0/1 spanning-tree portfast		Spanning Tree Portfast causes an interface configured as a layer 2 access port to enter the forwarding state immediately. Conf t int fa 0/1 spanning-tree portfast
	confirm with show spanning-tree interface Fastethernet 0/1.		confirm with show spanning-tree interface Fastethernet 0/1.
	Config the Basic Parameters of PVRST+ conf t spanning-tree mode rapid-pvst spanning-tree vlan 2 root primary spanning tree- vlan 3 root secondary		Config the Basic Parameters of PVRST+ conf t spanning-tree mode rapid-pvst spanning-tree vlan 2 root primary spanning tree- vlan 3 root secondary

	='''Multiple Spanning Tree		='''Multiple Spanning Tree'''=
	''='MST extends the IEEE 802.1w RST algorithm to multiple spanning trees. The main purpose of MST is to reduce the total number of spanning-tree instances.
			MST extends the IEEE 802.1w RST algorithm to multiple spanning trees. The main purpose of MST is to reduce the total number of spanning-tree instances.

West0476: /* STP initially converges on a logically loop-free network topology */

2012-02-06T15:21:47Z

STP initially converges on a logically loop-free network topology

← Older revision		Revision as of 15:21, 6 February 2012
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	='''STP initially converges on a logically loop-free network topology'''=		='''STP initially converges on a logically loop-free network topology'''=
	1) Elects one root bridge		1) Elects one root bridge

	2) Selects the root port on all nonroot bridges		2) Selects the root port on all nonroot bridges

	3) Selects the designated port on each segment		3) Selects the designated port on each segment

West0476: /* Elects One Root Bridge */

2012-02-06T15:21:33Z

Elects One Root Bridge

← Older revision		Revision as of 15:21, 6 February 2012
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	='''Elects One Root Bridge'''=		='''Elects One Root Bridge'''=
	• The protocol uses a process to elect a root bridge		• The protocol uses a process to elect a root bridge

	• Only one bridge acts as the root bridge in a given network per VLAN		• Only one bridge acts as the root bridge in a given network per VLAN

	• On the root bridge, all ports act as designated ports		• On the root bridge, all ports act as designated ports

	• Switch with lowest priority parameter is elected as root		• Switch with lowest priority parameter is elected as root

	• STP Step 2 (cont)		• STP Step 2 (cont)