CCNA3_M9_VLAN_Trunking_Protocol (1130774)
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CCNA – Semester3Module 9VLAN Trunking ProtocolObjectives• Origins and functions of VLAN trunking• Define VTP• Inter-VLAN routingTrunkingHistory of trunking• In radio technologies, a trunk is a singlecommunications line that carries multiple channels ofradio signals.Trunk in VLAN• The same principle of trunking is applied to networkswitching technologies.• A trunk is a physical and logical connectionbetween two switches across which network traffictravels.Trunking protocols• Trunking protocols were developed toeffectively manage the transfer of framesfrom different VLANs on a single physicalline.• Two types of trunking mechanisms exist:– frame filtering– frame tagging.Frame FilteringFrames Tagging• Every frame is appended with a tag or VLAN ID.• Each switch examines every frame’s VLAN ID beforeforwarding.• Frame’s VLAN ID is removed before transmitted toend stations• Requires lessadministration• Scalable to largenetworkTrunking Protocol•The most common tagging schemes for Ethernet segmentsare listed below:• ISL – Cisco proprietary Inter-Switch Link protocol.• 802.1Q – IEEE standard that will be focused on in this section.•Trunk ports speed must be at least 100MbpsVLANs and Trunking• Switch removes the identifierbefore the frame is transmittedto the target end station.• Frame tagging functions atLayer 2.• A trunk link does not belong toa specific VLAN.VLANs and Trunking• ISL is a protocol that maintains VLAN information astraffic flows between the switches.
With ISL, an Ethernetframe is encapsulated with a header that contains aVLAN ID.Trunking configurationTrunking modesShow port capabilities• Determine what encapsulation the port can support (orshow interfaces switchport).Show trunk• Verify that trunking has been configured and verifythe settings (or show interfaces trunk)VTPVTP Introduction• With VTP, VLAN configuration is consistentlymaintained across a common administrative domain.• VTP is a messaging protocol that uses Layer 2 trunkframes to manage the addition, deletion, and renamingof VLANs on a single domain.Trunk Links• VTP messages are encapsulated in either ISL or IEEE802.1Q protocol frames, and passed across trunk linksto other devices.VTP header• The VTP header varies, depending upon the type of VTPmessage, but generally, four items are found in all VTPmessages:– VTP protocol version: Either Version 1 or 2– VTP message type: Indicates one of four types– Management domain name length: Indicates size of the name thatfollows– Management domain name: The name configured for themanagement domainVTP modes• VTP switches operate in one of three modes:– Server– Client– TransparentVTP revision number•VLANs detected within theadvertisements serve asnotification to the switchthat traffic with the newlydefined VLAN IDs may beexpected.•VTP maintains its own NVRAM.
An erase startup-configuration clearsthe NVRAM of configuration commands, but not the VTP databaserevision number.To set the configuration revision number back to zero, the switchmust be rebooted.•VTP advertisement• Each switch advertises on its trunk ports, itsmanagement domain, configuration revisionnumber, the VLANs that it knows about, andcertain parameters for each known VLAN.• These advertisement frames are sent to amulticast address so that all neighboringdevices can receive the frames.VTP advertisements• There are two types of VTP advertisements:• Requests from clients that want information at bootup• Response from servers• There are three types of VTP messages:• Advertisement requests• Summary advertisements• Subset advertisementsVTP advertisementsVTP Implementation• By default, server and client Catalyst switches issuesummary advertisements every 5 minutes.• Subset advertisements contain detailed informationabout VLANs such as VTP version type, domain nameand related fields, and the configuration revisionnumber.
The following can trigger these advertisements:––––Creating or deleting a VLANSuspending or activating a VLANChanging the name of a VLANChanging the maximum transmission unit (MTU) of a VLANVTP Implementation• Advertisements may contain some or all of thefollowing information:– Management domain name. Advertisements with differentnames are ignored.– Configuration revision number.– Message Digest 5 (MD5) password.– Updater identity.VTP version• Two different versions of VTP are available,Version 1 and Version 2.• The two versions are not interoperable.• Configure the VTP version on a Cisco IOScommand-based switch:Switch#vlan databaseSwitch(vlan)#vtp v2-modeConfigure VTP domainSwitch(vlan)#vtp domain domain_nameSwitch(vlan)#vtp password passwordSwitch(vlan)#vtp {client | server | transparent}• The domain name can be between 1 and 32characters.• The password must be between 8 and 64characters long.Add switch to VTP domain••••Clear the configuration (erase startup)Clear the VTP file (delete flash:vlan.dat)Powercycle the switchesConfigure VTP mode and domain name (domainname can be learned automatically on clientswitches)• Password protect for the domain• Configure a trunk port that connect to a switchin the domain.Show vtp statusShow vtp countersInter-VLAN Routing OverviewBetween VLANsCommunicating between VLANsRouter on a Stick•Two of the most commonissues that arise in a multipleVLAN environment are:– The need for end user devices toreach non-local hosts– The need for hosts on differentVLANs to communicate•The router-on-a-stick designsemploy a single trunk link thatconnects the router to the restof the campus network.ISL and 802.1q••As the number of VLANsincreases on a network, thephysical approach of havingone router interface per VLANquickly becomes unscalable.Networks with many VLANsmust use VLAN trunking toassign multiple VLANs to asingle router interface.Inter-VLAN with trunking•••The primary advantage of using atrunk link is a reduction in thenumber of router and switchports used.Not only can this save money, itcan also reduce configurationcomplexity.Consequently, the trunkconnected router approach canscale to a much larger number ofVLANs than a one-link-per-VLANdesign.Subinterfaces and VLANsConfigure Inter-VLAN Routing• In order for inter-VLAN routing to work properly,all of the routers and switches involved mustsupport the same encapsulation.• To define subinterfaces on a physical interface,perform the following tasks:– Identify the interface.– Define the VLAN encapsulation.– Assign an IP address to the interface.Configure Inter-VLAN RoutingRouter(config)#interface fastethernet port-number.
subinterfacenumberRouter(config-if)#encapsulation dot1q vlan-numberRouter(config-if)#ip address ip-address subnet-maskInter-VLAN exampleSummary••••The origins and functions of VLAN trunkingIEEE 802.1Q & Cisco ISLDefinition of VLAN Trunking Protocol (VTP)The contents of VTP messages and the three VTPmodes• Configuring and verifying VTP on an IOS-basedswitch• Configuring inter-VLAN routing using subinterfaceson a router portLab 1: VLAN & VTP• Configure VTP domain CCNA,password class, version 2.• VLANs: Associate, Professional,Specialist• Trunk ports: f0/24Ports ->DefaultAssociateProfessionalSpecialistServer1 – 3, 64,5,8 – 127,13 – 1920 – 23Client2–91, 10 – 1515 – 18, 2019, 21 – 23Lab Topology• IP range: 172.20.0.0/16• Vlan Default (port 1 – 5) needs 5IPs• Vlan Sales (port 6 – 10) needs100 IPs• Vlan Engineer (port 11 – 15)needs 50 IPs• Vlan Marketing (port 16 – 23)needs 100 IPsCCNA3 – Module9.
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