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Transcript of CCNAV3.3 308
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CCNA Semester 3
Chapter 08Chap
ter 08
VLAN TRUNKINGVLAN TRUNKINGPROTOCOLPROTOCOL
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Table of ContentTable of Content
1 VTP2 Inter-VLAN routing overview
3 VLAN troubleshooting
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VTPVTP
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VTP conceptsVTP concepts
The role of VTP is to maintain VLAN
configuration consistency across a commonnetwork administration domain.
VTP is a messaging protocol that uses Layer 2trunk frames to manage the addition,deletion, and renaming of VLANs on a singledomain.
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A messaging system that advertises VLAN configuration information
Maintains VLAN configuration consistency throughout a commonadministrative domain
Sends advertisements on trunk ports only
VTP Protocol FeaturesVTP Protocol Features
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Forwardsadvertisements
Synchronizes
Not saved inNVRAM
Creates VLANs Modifies VLANs
Deletes VLANs
Sends/forwardsadvertisements
Synchronizes
Saved in NVRAM
Creates VLANs
Modifies VLANs
Deletes VLANs Forwardsadvertisements
Does notsynchronize
Saved in NVRAM
VTP ModesVTP Modes
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VTP Operation
VTP advertisements are sent as multicast frames.
VTP servers and clients are synchronized to the latest revision number.
VTP advertisements are sent every 5 minutes or when there is a change.
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VTP Pruning
Increases available bandwidth by reducing unnecessary flooded traffic
Example: Station A sends broadcast, and broadcast is flooded only toward
any switch with ports assigned to the red VLAN
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Three types of VTP messagesThree types of VTP messages
Summary advertisements
Advertisement requests
Subset advertisements
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Summary advertisementsSummary advertisements
Summary Advertisement1 2 3 4
Version Code Followers MgmtD len
Management domain name (zero-padded to32bytes)
Configuration revision number
Updater identifyUpdate timestamp (12 bytes)
MD5 digest (16 bytes)
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Advertisement requestAdvertisement request
Advertisement Request
1 2 3 4
Version Code Rsvd MgmtD len
Management domain name (zero-padded to32bytes)
Start value
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Subset advertisementSubset advertisement
Subset Advertisement
1 2 3 4
Version Code Seq-Num MgmtD len
Management domain name (zero-padded to32bytes)
Configuration revision number
Vlan-info field 1
:
Vlan-info field N
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Vlan-info field N formatVlan-info field N format
Info length Status Vlan-typeVlan-name len
ISL VLAN-id MTU size802.10 index
Vlan-name (padded with 0s to multiples of 4bytes)
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VTP domain name
VTP mode (server/client/transparent)VTP server mode is the default
VTP pruning VTP password
VTP trap
Use caution when adding a new switch to an existing domain.Add a new switch in client mode to prevent the new switch from
propagating incorrect VLAN information.
Use the delete vtp command to reset the VTP revision number.
VTP Configuration GuidelinesVTP Configuration Guidelines
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VTP configurationVTP configuration
Switch# vlan database
Switch(vlan)# vtp v2-modeSwitch(vlan)# vtp domain cisco
Switch(vlan)# vtp client/server/transparent
Switch# show vtp status
Switch# show vtp counters
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Creating a VTP Domain
wg_sw_1900#configure terminalEnter configuration commands, one per line. End with CNTL/Zwg_sw_1900(config)#vtp transparentwg_sw_1900(config)#vtp domain switchlab
wg_sw_1900(config)#vtp [server | transparent | client] [domaindomain-name] [trap {enable | disable}] [passwordpassword][pruning {enable | disable}]
Catalyst 1900
Catalyst 2950
wg_sw_2950#vlan databasewg_sw_2950(vlan)#vtp [ server | client | transparent ]wg_sw_2950(vlan)#vtp domain domain-namewg_sw_2950(vlan)#vtp passwordpasswordwg_sw_2950(vlan)#vtp pruningwg_sw_2950(vlan)#snmp-server enable traps vtpwg_sw_2950(vlan)#exit
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VTP Configuration ExampleVTP Configuration Example
wg_sw_1900(config)#vtp transparentwg_sw_1900(config)#vtp domain switchlab pruning enablewg_sw_1900(config)#exitwg_sw_1900#show vtpVTP version: 1
Configuration revision: 4Maximum VLANs supported locally: 1005
Number of existing VLANs: 6 VTP domain name : switchlab VTP password : VTP operating mode : Transparent VTP pruning mode : EnabledVTP traps generation : EnabledConfiguration last modified by: 0.0.0.0 at 00-00-0000
00:00:00wg_sw_1900#config terminalwg_sw_1900(config)#interface f0/26wg_sw_1900(config-if)#trunk on desirablewg_sw_1900(config-if)#exitwg_sw_1900(config)#exitwg_sw_1900#show trunk A
DISL state: On, Trunking: On, Encapsulation type: ISL
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INTER-VLAN ROUTING OVERVIEWINTER-VLAN ROUTING OVERVIEW
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VLAN-to-VLAN OverviewVLAN-to-VLAN Overview
Network layer devices combine multiple
broadcast domains.
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Physical and logical interfacesPhysical and logical interfaces
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Configuring inter-VLAN routingConfiguring inter-VLAN routing
Router(config)# interface fastethernet
port-number. Subinterface-number
Router(config-if)#encapsulation dot1q/isl vlan-
numberRouter(config-if)#ip address x.x.x.x y.y.y.y
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Routing Between VLANs with ISL TrunksRouting Between VLANs with ISL Trunks
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Routing Between VLANs with 802.1Q TrunksRouting Between VLANs with 802.1Q Trunks
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TROUBLESHOOTING VLANTROUBLESHOOTING VLAN
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VLAN troubleshooting processVLAN troubleshooting process
LEDs
(or networkmanageme
nt
equivalent)
O.K ?
Switch
configuratio
n OK?
Physicallink
connection
OK?
Vlan
configuration OK?
L2 path
betweenswitchs
OK?
Fix any problem withswitch hardware
Fix any problem withconfiguration statements
Check with CDP, fixany cabling problems
Fix any switch trunking or
ISL configuration problem
Fix any VLAN, spanning tree or
intermediate router problems
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Preventing broadcast stormsPreventing broadcast storms
Setting threshold values to high or lowdiscards excessive broadcast, multicast, orunicast MAC traffic.
Minimize the STP processes occurring
between devices.
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Troubleshooting VLANsTroubleshooting VLANs
Show vlan Show spanning-tree
Show sw-vlan
Debug sw-vlan packet
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Scenario 1:Scenario 1: A trunk link cannot be established between aA trunk link cannot be established between a
switch and a routerswitch and a router
1. Make sure that the port is connected and notreceiving any physical-layer, alignment orframe-check-sequence (FCS) errors.
2. Verify that the duplex and speed are setproperly between the switch and the router.
3. Configure the physical router interface with
one subinterface for each VLAN that willroute traffic.
4. Confirm that the router is running an IOSrelease that supports trunking.
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Scenario 2:Scenario 2: VTP is not correctly propagating VLANVTP is not correctly propagating VLAN
configuration changesconfiguration changes
1. Make sure the switches are connectedthrough trunk links.
2. Make sure the VTP domain name is thesame on all switches that need tocommunicate with each other.
3. Check the VTP mode of the switch.
4. If using VTP passwords, the same passwordmust be configured on all switches in theVTP domain.
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Scenario 3:Scenario 3: Dropped packets and loopsDropped packets and loops
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SummarySummary
Definition of VLAN Trunking Protocol (VTP)
Configuring inter-VLAN routing usingsubinterfaces on a router port
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Q&AQ&A