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1. M S RAMAIAH INSTITUTEM S RAMAIAH INSTITUTE
OF TECHNOLOGYOF TECHNOLOGY
Department of INFORMATION SCIENCE AND ENGINEERING
Subject : Data Communication
Topic : Virtual LAN
Submitted by : Shubhada Bhatta
Sushma S
Vidya B M
2. VLAN Overview (1)VLAN Overview (1)
• A VLAN allows a network administrator toA VLAN allows a network administrator to create groups ofcreate groups of
logically networked devices that act as if they are on theirlogically networked devices that act as if they are on their
own independent networkown independent network, even if they share a common, even if they share a common
infrastructure with other VLANs.infrastructure with other VLANs.
• Using VLANs, you canUsing VLANs, you can logically segment switchedlogically segment switched
networksnetworks based on functions, departments, or projectbased on functions, departments, or project
teams.teams.
• You can also use a VLAN toYou can also use a VLAN to geographically structure yourgeographically structure your
networknetwork to support the growing reliance of companies onto support the growing reliance of companies on
home-based workers.home-based workers.
• These VLANs allow the network administrator toThese VLANs allow the network administrator to
implementimplement access and security policiesaccess and security policies to particularto particular
groups of users.groups of users.
4. VLAN in detailsVLAN in details (1)(1)
• A VLAN is aA VLAN is a logically separate IP subnetworklogically separate IP subnetwork..
• VLANs allow multiple IP networks and subnets toVLANs allow multiple IP networks and subnets to
exist on the same switched network.exist on the same switched network.
• For computers to communicate on the sameFor computers to communicate on the same
VLAN, eachVLAN, each must have an IP address and amust have an IP address and a
subnet mask that is consistent for that VLANsubnet mask that is consistent for that VLAN..
• The switch has to be configured with the VLANThe switch has to be configured with the VLAN
and each port in the VLAN must be assigned toand each port in the VLAN must be assigned to
the VLAN.the VLAN.
5. VLAN in detailsVLAN in details (2)(2)
• A switch port with a singular VLAN configured onA switch port with a singular VLAN configured on
it is called anit is called an access portaccess port..
• Remember, just because two computers areRemember, just because two computers are
physically connected to the same switch doesphysically connected to the same switch does
not mean that they can communicate.not mean that they can communicate.
• DevicesDevices on two separate networks and subnetson two separate networks and subnets
must communicate via a routermust communicate via a router (Layer 3),(Layer 3),
whether or not VLANs are used.whether or not VLANs are used.
7. Benefits of VLAN (1)Benefits of VLAN (1)
• SecuritySecurity - Groups that have sensitive data are- Groups that have sensitive data are
separated from the rest of the network,separated from the rest of the network,
decreasing the chances of confidentialdecreasing the chances of confidential
information breaches.information breaches.
– Faculty computers are on VLAN 10 and completelyFaculty computers are on VLAN 10 and completely
separated from student and guest data traffic.separated from student and guest data traffic.
• Cost reductionCost reduction - Cost savings result from less- Cost savings result from less
need for expensive network upgrades and moreneed for expensive network upgrades and more
efficient use of existing bandwidth and uplinks.efficient use of existing bandwidth and uplinks.
8. Benefits of VLAN (2)Benefits of VLAN (2)
• Higher performanceHigher performance - Dividing flat Layer 2- Dividing flat Layer 2
networks into multiple logical workgroupsnetworks into multiple logical workgroups
(broadcast domains)(broadcast domains) reduces unnecessary trafficreduces unnecessary traffic
on the network and boosts performanceon the network and boosts performance..
• Broadcast storm mitigationBroadcast storm mitigation - Dividing a network- Dividing a network
into VLANs reduces the number of devices thatinto VLANs reduces the number of devices that
may participate in a broadcast storm.may participate in a broadcast storm.
– In the figure you can see that although there are sixIn the figure you can see that although there are six
computers on this network, there are only threecomputers on this network, there are only three
broadcast domains: Faculty, Student, and Guest.broadcast domains: Faculty, Student, and Guest.
10. Benefits of VLAN (4)Benefits of VLAN (4)
• Improved IT staff efficiencyImproved IT staff efficiency - VLANs make it- VLANs make it
easier to manage the network because users witheasier to manage the network because users with
similar network requirements share the samesimilar network requirements share the same
VLAN.VLAN.
– When you provision a new switch, all the policies andWhen you provision a new switch, all the policies and
procedures already configured for the particular VLANprocedures already configured for the particular VLAN
are implemented when the ports are assigned.are implemented when the ports are assigned.
– It is also easy for the IT staff to identify the function of aIt is also easy for the IT staff to identify the function of a
VLAN by giving it an appropriate name.VLAN by giving it an appropriate name.
– In the figure, for easy identification VLAN 20 could beIn the figure, for easy identification VLAN 20 could be
named "Student", VLAN 10 could be named "Faculty",named "Student", VLAN 10 could be named "Faculty",
and VLAN 30 "Guest."and VLAN 30 "Guest."
11. Benefits of VLAN (5)Benefits of VLAN (5)
• Simpler project or application managementSimpler project or application management --
VLANs aggregate users and network devices toVLANs aggregate users and network devices to
support business or geographic requirements.support business or geographic requirements.
– Having separate functions makes managing aHaving separate functions makes managing a
project or working with a specializedproject or working with a specialized
application easier, for example, an e-learningapplication easier, for example, an e-learning
development platform for faculty.development platform for faculty.
– It is also easier to determine the scope of theIt is also easier to determine the scope of the
effects of upgrading network services.effects of upgrading network services.
12. Benefits of VLAN (6)Benefits of VLAN (6)
• Simpler project or application managementSimpler project or application management --
VLANs aggregate users and network devices toVLANs aggregate users and network devices to
support business or geographic requirements.support business or geographic requirements.
– Having separate functions makes managing aHaving separate functions makes managing a
project or working with a specializedproject or working with a specialized
application easier, for example, an e-learningapplication easier, for example, an e-learning
development platform for faculty.development platform for faculty.
– It is also easier to determine the scope of theIt is also easier to determine the scope of the
effects of upgrading network services.effects of upgrading network services.
13. Introducing VLANsIntroducing VLANs (1)(1)
• VLAN ID Ranges -VLAN ID Ranges - Access VLANs are divided into either aAccess VLANs are divided into either a
normal range or an extended range.normal range or an extended range.
• Normal Range VLANs -Normal Range VLANs -Used in small- and medium-sizedUsed in small- and medium-sized
business and enterprise networks.business and enterprise networks.
• Identified by a VLAN ID between 1 and 1005.Identified by a VLAN ID between 1 and 1005.
– IDs 1002 through 1005 are reserved for Token Ring and FDDI VLANs.IDs 1002 through 1005 are reserved for Token Ring and FDDI VLANs.
– IDs 1 and 1002 to 1005 are automatically created and cannot beIDs 1 and 1002 to 1005 are automatically created and cannot be
removed.removed.
– Configurations are stored within a VLAN database file, calledConfigurations are stored within a VLAN database file, called vlan.datvlan.dat..
– The vlan.dat file is located in the flash memory of the switch.The vlan.dat file is located in the flash memory of the switch.
• The VLAN trunking protocol (VTP), which helps manageThe VLAN trunking protocol (VTP), which helps manage
VLAN configurations between switches, can only learnVLAN configurations between switches, can only learn
normal range VLANs and stores them in the VLAN databasenormal range VLANs and stores them in the VLAN database
file.file.
14. Introducing VLANsIntroducing VLANs (2)(2)
• Extended Range VLANs -Extended Range VLANs - Enable serviceEnable service
providers to extend their infrastructure to a greaterproviders to extend their infrastructure to a greater
number of customers.number of customers.
– Some global enterprises could be large enough to needSome global enterprises could be large enough to need
extended range VLAN IDs.extended range VLAN IDs.
• Are identified by a VLAN ID betweenAre identified by a VLAN ID between 1006 and1006 and
4094.4094.
• Support fewer VLAN features than normal rangeSupport fewer VLAN features than normal range
VLANs.VLANs.
• Are saved in theAre saved in the running configuration filerunning configuration file..
• VTPVTP does not learndoes not learn extended range VLANs.extended range VLANs.
15. Introducing VLANsIntroducing VLANs (3)(3)
• 255 VLANs Configurable255 VLANs Configurable
– One Cisco Catalyst 2960 switch can support upOne Cisco Catalyst 2960 switch can support up
to 255 normal range and extended rangeto 255 normal range and extended range
VLANs, although the number configured affectsVLANs, although the number configured affects
the performance of the switch hardware.the performance of the switch hardware.
17. Types of VLANs -Types of VLANs - Data VLANData VLAN
(1)(1)
• Data VLANData VLAN -- a VLAN that is configured to carrya VLAN that is configured to carry
only user-generated traffic.only user-generated traffic.
• It is common practice to separateIt is common practice to separate voice andvoice and
management trafficmanagement traffic from data traffic.from data traffic.
• A data VLAN is sometimes referred to as aA data VLAN is sometimes referred to as a useruser
VLANVLAN..
19. Types of VLANs-Types of VLANs- Default VLANDefault VLAN (1)(1)
• All switch ports becomeAll switch ports become a member of the defaulta member of the default
VLAN after the initial boot up of the switchVLAN after the initial boot up of the switch..
– Having all the switch ports participate in the defaultHaving all the switch ports participate in the default
VLAN makes them all part of the same broadcastVLAN makes them all part of the same broadcast
domain.domain.
– This allows any device connected to any switch port toThis allows any device connected to any switch port to
communicate with other devices on other switch ports.communicate with other devices on other switch ports.
– The default VLAN for Cisco switches is VLAN 1.The default VLAN for Cisco switches is VLAN 1.
– VLAN 1 has all the features of any VLAN, except thatVLAN 1 has all the features of any VLAN, except that
you cannot rename it and you can not delete it.you cannot rename it and you can not delete it.
20. Types of VLANsTypes of VLANs-- Default VLANDefault VLAN (2)(2)
– Layer 2 control traffic, such as CDP and spanning treeLayer 2 control traffic, such as CDP and spanning tree
protocol trafficprotocol traffic, will always be associated with VLAN 1, will always be associated with VLAN 1
- this cannot be changed.- this cannot be changed.
– In the figure, VLAN 1 traffic is forwarded over theIn the figure, VLAN 1 traffic is forwarded over the
VLAN trunks connecting the S1, S2, and S3 switches.VLAN trunks connecting the S1, S2, and S3 switches.
– It is a security best practice to change the defaultIt is a security best practice to change the default
VLAN to a VLAN other than VLAN 1VLAN to a VLAN other than VLAN 1; this entails; this entails
configuring all the ports on the switch to be associatedconfiguring all the ports on the switch to be associated
with a default VLAN other than VLAN 1.with a default VLAN other than VLAN 1.
22. Types of VLANsTypes of VLANs -- Native VLANNative VLAN (1)(1)
• A native VLAN is assigned to an 802.1Q trunkA native VLAN is assigned to an 802.1Q trunk
portport..
• An 802.1Q trunk port supports traffic coming fromAn 802.1Q trunk port supports traffic coming from
many VLANs (tagged traffic) as well as traffic thatmany VLANs (tagged traffic) as well as traffic that
does not come from a VLAN (untagged traffic).does not come from a VLAN (untagged traffic).
• The 802.1Q trunk port places untagged traffic onThe 802.1Q trunk port places untagged traffic on
the native VLAN.the native VLAN.
• In the figure, the native VLAN is VLAN 99.In the figure, the native VLAN is VLAN 99.
• Untagged traffic is generated by a computerUntagged traffic is generated by a computer
attached to a switch port that is configured withattached to a switch port that is configured with
the native VLAN.the native VLAN.
23. Types of VLANsTypes of VLANs -- Native VLANNative VLAN (2)(2)
• Native VLANs are set out in the IEEE 802.1QNative VLANs are set out in the IEEE 802.1Q
specification to maintain backward compatibilityspecification to maintain backward compatibility
with untagged traffic common to legacy LANwith untagged traffic common to legacy LAN
scenarios.scenarios.
• For our purposes, a native VLAN serves as aFor our purposes, a native VLAN serves as a
common identifier on opposing ends of a trunkcommon identifier on opposing ends of a trunk
link.link.
• It is a best practice to use a VLAN other thanIt is a best practice to use a VLAN other than
VLAN 1 as the native VLAN.VLAN 1 as the native VLAN.
25. Types of VLANsTypes of VLANs -- ManagementManagement
VLANVLAN (1)(1)
• A management VLAN is any VLAN you configure toA management VLAN is any VLAN you configure to
access the management capabilities of a switchaccess the management capabilities of a switch..
• VLAN 1 would serve as the management VLAN ifVLAN 1 would serve as the management VLAN if
you did not proactively define a unique VLAN toyou did not proactively define a unique VLAN to
serve as the management VLAN.serve as the management VLAN.
• You assign the management VLAN an IP addressYou assign the management VLAN an IP address
and subnet mask.and subnet mask.
– A switch can be managed via HTTP, Telnet, SSH, orA switch can be managed via HTTP, Telnet, SSH, or
SNMP.SNMP.
• VLAN 1 is normally used as the default VLAN,VLAN 1 is normally used as the default VLAN,
– VLAN1 would be a bad choice as the managementVLAN1 would be a bad choice as the management
VLAN; you wouldn't want an arbitrary user connecting toVLAN; you wouldn't want an arbitrary user connecting to
a switch to default to the management VLAN.a switch to default to the management VLAN.
27. Types of VLANsTypes of VLANs -- Voice VLANVoice VLAN (1)(1)
• It is easy to appreciate why a separate VLAN isIt is easy to appreciate why a separate VLAN is
neededneeded to support Voice over IPto support Voice over IP (VoIP).(VoIP).
• VoIP traffic requires:VoIP traffic requires:
– Assured bandwidth to ensure voice qualityAssured bandwidth to ensure voice quality
– Transmission priority over other types of networkTransmission priority over other types of network
traffictraffic
– Ability to be routed around congested areas on theAbility to be routed around congested areas on the
networknetwork
– Delay of less than 150 milliseconds (ms) across theDelay of less than 150 milliseconds (ms) across the
networknetwork
29. Types of VLANsTypes of VLANs -- Voice VLANVoice VLAN (3)(3)
• A Cisco Phone is a SwitchA Cisco Phone is a Switch
• The Cisco IP Phone contains an integrated three-portThe Cisco IP Phone contains an integrated three-port
10/100 switch as shown in the Figure. The ports provide10/100 switch as shown in the Figure. The ports provide
dedicated connections to these devices:dedicated connections to these devices:
• Port 1 connects to the switch or other voice-over-IPPort 1 connects to the switch or other voice-over-IP
(VoIP) device.(VoIP) device.
• Port 2 is an internal 10/100 interface that carries the IPPort 2 is an internal 10/100 interface that carries the IP
phone traffic.phone traffic.
• Port 3 (access port) connects to a PC or other device.Port 3 (access port) connects to a PC or other device.
32. Types of VLANsTypes of VLANs -- Network trafficNetwork traffic
type (1)type (1)
• Network Management and Control TrafficNetwork Management and Control Traffic
• Many different types of network managementMany different types of network management
and control traffic can be present on theand control traffic can be present on the
network, such as Cisco Discovery Protocolnetwork, such as Cisco Discovery Protocol
(CDP) updates, Simple Network Management(CDP) updates, Simple Network Management
Protocol (SNMP) traffic, and Remote MonitoringProtocol (SNMP) traffic, and Remote Monitoring
(RMON) traffic.(RMON) traffic.
33. Types of VLANsTypes of VLANs -- Network trafficNetwork traffic
type (2)type (2)
34. Types of VLANsTypes of VLANs -- Network trafficNetwork traffic
type (3)type (3)
• IP TelephonyIP Telephony
• The types of IP telephony traffic are signalingThe types of IP telephony traffic are signaling
traffic and voice traffic.traffic and voice traffic.
• Signaling traffic is, responsible for call setup,Signaling traffic is, responsible for call setup,
progress, and teardown, and traverses theprogress, and teardown, and traverses the
network end to end.network end to end.
• The other type of telephony traffic consists ofThe other type of telephony traffic consists of
data packets of the actual voice conversation.data packets of the actual voice conversation.
• Data traffic should be associated with a dataData traffic should be associated with a data
VLAN (other than VLAN 1), and voice traffic isVLAN (other than VLAN 1), and voice traffic is
associated with a voice VLAN.associated with a voice VLAN.
35. Types of VLANsTypes of VLANs -- Network trafficNetwork traffic
type (4)type (4)
36. Types of VLANsTypes of VLANs -- Network trafficNetwork traffic
type (5)type (5)
• IP MulticastIP Multicast
• IP multicast traffic is sent fromIP multicast traffic is sent from a particular source addressa particular source address
to a multicast groupto a multicast group that is identified by a single IP and MACthat is identified by a single IP and MAC
destination-group address pair.destination-group address pair.
• Multicast traffic can produceMulticast traffic can produce a large amount of dataa large amount of data
streaming across the network.streaming across the network.
• When the network must support multicast traffic,When the network must support multicast traffic, VLANsVLANs
should be configured to ensure multicast traffic only goes toshould be configured to ensure multicast traffic only goes to
those user devicesthose user devices that use the service provided, such asthat use the service provided, such as
remote video or audio applications.remote video or audio applications.
• Routers must be configured to ensure that multicast traffic isRouters must be configured to ensure that multicast traffic is
forwarded to the network areas where it is requested.forwarded to the network areas where it is requested.
37. Types of VLANsTypes of VLANs -- Network trafficNetwork traffic
type (6)type (6)
38. Types of VLANsTypes of VLANs -- Network trafficNetwork traffic
type (7)type (7)
• Normal DataNormal Data
• Normal data traffic is related to file creation andNormal data traffic is related to file creation and
storage, print services, e-mail database access,storage, print services, e-mail database access,
and other shared network applications that areand other shared network applications that are
common to business uses.common to business uses.
• VLANs are a natural solution for this type ofVLANs are a natural solution for this type of
traffic because you can segment users by theirtraffic because you can segment users by their
functions or geographic area to more easilyfunctions or geographic area to more easily
manage their specific needs.manage their specific needs.
39. Types of VLANsTypes of VLANs -- Network trafficNetwork traffic
type (8)type (8)
• Scavenger ClassScavenger Class
• The Scavenger class is intended to provide less-than best-The Scavenger class is intended to provide less-than best-
effort services to certain applicationseffort services to certain applications..
• Applications assigned to this class haveApplications assigned to this class have little or nolittle or no
contribution to the organizational objectivescontribution to the organizational objectives of theof the
enterprise and are typically entertainment oriented inenterprise and are typically entertainment oriented in
nature.nature.
• These includeThese include peer-to-peer media-sharing applicationspeer-to-peer media-sharing applications
(KaZaa, Morpheus, Groekster, Napster, iMesh, and so on),(KaZaa, Morpheus, Groekster, Napster, iMesh, and so on),
gaming applicationsgaming applications (Doom, Quake, Unreal Tournament,(Doom, Quake, Unreal Tournament,
and so on), and any entertainment video applications.and so on), and any entertainment video applications.
40. VLAN Switch Port (1)VLAN Switch Port (1)
• Static VLANStatic VLAN - Ports on a switch are manually assigned to a- Ports on a switch are manually assigned to a
VLAN.VLAN.
– Static VLANs are configured using the Cisco CLI.Static VLANs are configured using the Cisco CLI.
– This can also be accomplished with GUI management applications,This can also be accomplished with GUI management applications,
such as the Cisco Network Assistant.such as the Cisco Network Assistant.
• Dynamic VLANDynamic VLAN - This mode is not widely used in production- This mode is not widely used in production
networks.networks.
– A dynamic port VLAN membership is configured using a specialA dynamic port VLAN membership is configured using a special
server called a VLAN Membership Policy Server (VMPS).server called a VLAN Membership Policy Server (VMPS).
– With the VMPS, you assign switch ports to VLANs dynamically,With the VMPS, you assign switch ports to VLANs dynamically,
based on the source MAC address of the device connected to thebased on the source MAC address of the device connected to the
port.port.
– The benefit comes when you move a host from a port on one switchThe benefit comes when you move a host from a port on one switch
in the network to a port on another switch in the network-the switchin the network to a port on another switch in the network-the switch
dynamically assigns the new port to the proper VLAN for that host.dynamically assigns the new port to the proper VLAN for that host.
41. VLAN Switch Port (2)VLAN Switch Port (2)
• Voice VLANVoice VLAN - A port is configured to be in voice mode so- A port is configured to be in voice mode so
that it can support an IP phone attached to it.that it can support an IP phone attached to it.
• It is assumed that the network has been configured toIt is assumed that the network has been configured to
ensure that voice traffic can be transmitted withensure that voice traffic can be transmitted with a prioritya priority
status over the network.status over the network.
• When a phone is first plugged into a switch port that is inWhen a phone is first plugged into a switch port that is in
voice mode, the switch port sends messages to the phonevoice mode, the switch port sends messages to the phone
providing the phone with the appropriate voice VLAN IDproviding the phone with the appropriate voice VLAN ID
and configuration.and configuration.
• The IP phone tags the voice frames with the voice VLAN IDThe IP phone tags the voice frames with the voice VLAN ID
and forwards all voice traffic through the voice VLAN.and forwards all voice traffic through the voice VLAN.
48. VLAN Trunk (1)VLAN Trunk (1)
• A trunk is a point-to-point link between one orA trunk is a point-to-point link between one or
more Ethernet switch interfaces and anothermore Ethernet switch interfaces and another
networking devicenetworking device, such as a router or a switch., such as a router or a switch.
• Ethernet trunks carryEthernet trunks carry the traffic of multiple VLANsthe traffic of multiple VLANs
over a single linkover a single link..
• A VLAN trunk allows you to extend the VLANsA VLAN trunk allows you to extend the VLANs
across an entire network.across an entire network.
• Cisco supportsCisco supports IEEE 802.1QIEEE 802.1Q for coordinatingfor coordinating
trunks on Fast Ethernet and Gigabit Ethernettrunks on Fast Ethernet and Gigabit Ethernet
interfaces.interfaces.
52. VLAN Trunk - 802.1Q FrameVLAN Trunk - 802.1Q Frame
tagging (1)tagging (1)
• The VLAN tag fieldThe VLAN tag field consists of anconsists of an EtherTypeEtherType
field, a tag control information field,and the FCSfield, a tag control information field,and the FCS
fieldfield..
• EtherType fieldEtherType field
– Set to the hexadecimal value of 0x8100.Set to the hexadecimal value of 0x8100.
– This value is called the tag protocol ID (TPID) value.This value is called the tag protocol ID (TPID) value.
– With the EtherType field set to the TPID value, theWith the EtherType field set to the TPID value, the
switch receiving the frame knows to look forswitch receiving the frame knows to look for
information in the tag control information field.information in the tag control information field.
53. VLAN Trunk - 802.1Q FrameVLAN Trunk - 802.1Q Frame
tagging (2)tagging (2)
• Tag control information fieldTag control information field
– 3 bits of user priority3 bits of user priority - Used by the 802.1p standard,- Used by the 802.1p standard,
which specifies how to provide expeditedwhich specifies how to provide expedited
transmission of Layer 2 frames.transmission of Layer 2 frames.
– 1 bit of Canonical Format Identifier (CFI)1 bit of Canonical Format Identifier (CFI) - Enables- Enables
Token Ring frames to be carried across Ethernet linksToken Ring frames to be carried across Ethernet links
easily.easily.
– 12 bits of VLAN ID (VID)12 bits of VLAN ID (VID) - VLAN identification- VLAN identification
numbers; supports up to 4096 VLAN IDs.numbers; supports up to 4096 VLAN IDs.
• FCS fieldFCS field
– After the switch inserts the EtherType and tag controlAfter the switch inserts the EtherType and tag control
information fields, it recalculates the FCS values andinformation fields, it recalculates the FCS values and
inserts it into the frame.inserts it into the frame.
55. VLAN Trunk –Native VLAN (1)VLAN Trunk –Native VLAN (1)
• Tagged Frames on the Native VLANTagged Frames on the Native VLAN
• Control traffic sent on the native VLAN should beControl traffic sent on the native VLAN should be
untaggeduntagged..
• If an 802.1Q trunk port receives a tagged frameIf an 802.1Q trunk port receives a tagged frame
on the native VLAN, iton the native VLAN, it dropsdrops the frame.the frame.
– Consequently, when configuring a switch port on aConsequently, when configuring a switch port on a
Cisco switch, you need to identify these devices andCisco switch, you need to identify these devices and
configure them so that they do not send taggedconfigure them so that they do not send tagged
frames on the native VLAN.frames on the native VLAN.
56. VLAN Trunk –Native VLAN (2)VLAN Trunk –Native VLAN (2)
• Untagged Frames on the Native VLANUntagged Frames on the Native VLAN
• When a Cisco switch trunk port receives untagged framesWhen a Cisco switch trunk port receives untagged frames
it forwards those frames to the native VLAN.it forwards those frames to the native VLAN.
• The default native VLAN is VLAN 1.The default native VLAN is VLAN 1.
• When you configure an 802.1Q trunk port, a default PortWhen you configure an 802.1Q trunk port, a default Port
VLAN ID (PVID) is assigned the value of the native VLANVLAN ID (PVID) is assigned the value of the native VLAN
ID.ID.
• All untagged traffic coming in or out of the 802.1Q port isAll untagged traffic coming in or out of the 802.1Q port is
forwarded based on the PVID value.forwarded based on the PVID value.
– For example, if VLAN 99 is configured as the native VLAN, theFor example, if VLAN 99 is configured as the native VLAN, the
PVID is 99 and all untagged traffic is forward to VLAN 99.PVID is 99 and all untagged traffic is forward to VLAN 99.
– If the native VLAN has not been reconfigured, the PVID value isIf the native VLAN has not been reconfigured, the PVID value is
set to VLAN 1.set to VLAN 1.
67. Managing Port (2)Managing Port (2)
• Delete VLANsDelete VLANs
• Alternatively, the entire vlan.dat file can beAlternatively, the entire vlan.dat file can be
deleted using the commanddeleted using the command delete flash:vlan.datdelete flash:vlan.dat
from privileged EXEC mode.from privileged EXEC mode.
• After the switch is reloaded, the previouslyAfter the switch is reloaded, the previously
configured VLANs will no longer be present.configured VLANs will no longer be present.
• This effectively places the switch into is "factoryThis effectively places the switch into is "factory
default" concerning VLAN configurations.default" concerning VLAN configurations.
