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CCNA 200-120 Training2.8 Identify enhanced switching technologies

Jose Luis Flores / Amel Walkinshaw

Aug, 2015

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2.0 LAN Switching Technologies

2.8 Identify enhanced switching technologies 2.8.a RSTP 2.8.b PVSTP 2.8.c Etherchannels

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2.8 Identify enhanced switching technologies

The 802.1D Spanning Tree Protocol (STP) standard was designed at a time when the recovery of connectivity after an outage within a minute or so was considered adequate performance. With the advent of Layer 3 switching in LAN environments, bridging now competes with routed solutions where protocols, such as Open Shortest Path First (OSPF) and Enhanced Interior Gateway Routing Protocol (EIGRP), are able to provide an alternate path in less time.

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2.8 Identify enhanced switching technologies

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2.8 Identify enhanced switching technologies

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2.8 Identify enhanced switching technologies

Which switch provides the spanning-tree designated port role for the network segment that services the printers?

A. Switch1B. Switch2C. Switch3D. Switch4

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Key Topics

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udld aggressive

spanning-tree mode rapid-pvstspanning-tree portfast defaultspanning-tree portfast bpduguard defaultno spanning-tree optimize bpdu transmission

On interface:

description XXXXX power inline never switchport access vlan XXX switchport mode access no logging event link-status no snmp trap link-status no mdix auto spanning-tree portfast spanning-tree guard loop

Check Bug CSCee70806 athttp://www.cisco.com/cgi-bin/Support/Bugtool/launch_bugtool.pl____________________Release Notes"no spanning-tree optimize bpdu transmission" cannot be removed from the "show running" output.

Best practices:

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Best practices:

errdisable recovery cause udlderrdisable recovery cause bpduguarderrdisable recovery interval (time in seconds)

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PVST Operation In a PVST+ environment, you can tune the spanning-tree

parameters so that half the VLANs forward on each uplink trunk.

You do this by configuring one switch to be elected the root bridge for hal of the VLANs in the network and a second switch to be elected the root bridge for the other half of the VLANs

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PVST Operation

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PVST Operation Switched networks running PVST+ have the following

characteristics:− Configured PVST per VLAN allows redundant links to be fully utilized.− Each additional spanning-tree instance for a VLAN adds more CPU

cycles to all switches in the network

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PVST OperationPVST Port States

Operation Allowed Blocking Listening Learning Forwarding Disabled

Can receive and process BPDUs

Yes Yes Yes Yes No

Can forward data frames received on interface

No No No Yes No

Can forward data frames switched from another interface

No No No Yes No

Can learn MAC addresses

No No Yes Yes NO

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PVST OperationExtended System ID

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PVST OperationBridge ID for PVST+ with Extended System ID

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Rapid PVST + Operation In Rapid PVST+, a single instance of RSTP runs for each VLAN.

This is why Rapid PVST+ has a very high demand for switch resources (CPU cycles and RAM)

Rapid PVST+ is simply the Cisco Implementation of RSTP on a per-VLAN basis.

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Rapid PVST + Operation With RSTP, IEEE improved the convergence performance of

STP from 50 seconds to less than 10 seconds with its definition of Rapid STP (RSTP) in the standard 802.1w.

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Which two states are the port states when RSTP has converged? (Choose two. )

A. discardingB. listeningC. learningD. forwardingE. disabled

2.8 Identify enhanced switching technologies

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Rapid PVST + Operation RSTP is identical to STP in the following ways: It elects the root switch using the same parameters and

tiebreakers. It elects the root port on non-root switches with the same

rules. It elects designated ports on each LAN segment with the

same rules. It places each port in either forwarding or discarding state,

although RSTP calls the blocking state the discarding state.

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RSTP and STP Port States

Operational State

STP State802.1D

RSTP State802.1w

Forwards Data Frames in This State?

Enabled Blocking Discarding No

Enabled Listening Discarding No

Enabled Learning Learning No

Enabled Forwarding Forwarding Yes

Disabled Disabled Discarding No

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2.8 Identify enhanced switching technologies

Port Roles The role is now a variable assigned to a given port. The root port and designated port roles remain, while the blocking port role is split into the backup and alternate port roles. The Spanning Tree Algorithm (STA) determines the role of a port based on Bridge Protocol Data Units (BPDUs). In order to simplify matters, the thing to remember about a BPDU is there is always a method to compare any two of them and decide whether one is more useful than the other. This is based on the value stored in the BPDU and occasionally on the port on which they are received. This considered, the information in this section explains practical approaches to port roles.

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2.8 Identify enhanced switching technologies

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2.8 Identify enhanced switching technologies

EtherChannel mode ON

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2.8 Identify enhanced switching technologies

Ciscozine_SW1Ciscozine_SW1# configure terminalCiscozine_SW1(config)# interface range fastethernet0/0 -2Ciscozine_SW1(config-if-range)# switchport mode trunkCiscozine_SW1(config-if-range)# switchport access vlan 10Ciscozine_SW1(config-if-range)# channel-group 1 mode onCiscozine_SW1(config-if-range)# exitCiscozine_SW1(config)# exitCiscozine_SW1# write

Ciscozine_SW2Ciscozine_SW2# configure terminalCiscozine_SW2(config)# interface range fastethernet0/0 -2Ciscozine_SW2(config-if-range)# switchport mode trunkCiscozine_SW2(config-if-range)# switchport access vlan 10Ciscozine_SW2(config-if-range)# channel-group 1 mode onCiscozine_SW2(config-if-range)# exitCiscozine_SW2(config)# exitCiscozine_SW2# write

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2.8 Identify enhanced switching technologies

STP/EtherChannel CostSpanning-tree reproduces the increased bandwidth provided by EtherChannel. The default cost for a 100 Mbps link is 19 and if a port-channel is created that has only two 100 Mbps links, the spanning-tree cost will be 9.

A port-channel with six or more 100 Mbps physical ports will have an STP cost of 5. The cost is calculated based on the number of ports assigned to the port-channel. see table below:

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2.8 Identify enhanced switching technologies

A network administrator is configuring an EtherChannel between SW1 and SW2. The SW1 configuration is shown.What is the correct configuration for SW2?

A. interface FastEthernet 0/1 channel-group 1 mode active switchport trunk encapsulation dot1q switchport mode trunk interface FastEthernet 0/2 channel-group 1 mode active switchport trunk encapsulation dot1q switchport mode trunkB. interface FastEthernet 0/1 channel-group 2 mode auto switchport trunk encapsulation dot1q switchport mode trunk interface FastEthernet 0/2 channel-group 2 mode auto switchport trunk encapsulation dot1q switchport mode trunkC. interface FastEthernet 0/1 channel-group 1 mode desirable switchport trunk encapsulation dot1q switchport mode trunk interface FastEthernet 0/2 channel-group 1 mode desirable switchport trunk encapsulation dot1q switchport mode trunkD. interface FastEthernet 0/1 channel-group 1 mode passive switchport trunk encapsulation dot1q switchport mode trunk interface FastEthernet 0/2 channel-group 1 mode passive switchport trunk encapsulation dot1q switchport mode trunk

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2.8 Identify enhanced switching technologies

What parameter can be different on ports within an EtherChannel?

A. speedB. DTP negotiation settingsC. trunk encapsulationD. duplex

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2.8 Identify enhanced switching technologies

If the devices produced the given output, what is the cause of the EtherChannel problem?

A. SW1's Fa0/1 interface is administratively shut down.B. There is an encapsulation mismatch between SW1's Fa0/1 and SW2's Fa0/1 interfaces.C. There is an MTU mismatch between SW1's Fa0/1 and SW2's Fa0/1 interfaces.D. There is a speed mismatch between SW1's Fa0/1 and SW2's Fa0/1 interfaces.

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2.8 Identify enhanced switching technologies

A network administrator creates a layer 3 EtherChannel, bundling four interfaces into channel group1.

On what interface is the IP address configured?

A. the port-channel 1 interfaceB. the highest number member interfaceC. all member interfacesD. the lowest number member interface

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Bibliography

• http://www.cisco.com/c/en/us/support/docs/lan-switching/spanning-tree-protocol/24062-146.html• http://blog.ine.com/wp-content/uploads/2010/04/understanding-stp-rstp-convergence.pdf• http://infodocs.net/articulo/networking/etherchannel-entre-switches-cisco• http://orbit-computer-solutions.com/Understanding-and-Configuring-EtherChannel.php

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Q&A