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VLAN
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= Virtual Lan
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= Broadcast Domain
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= Logical Network subnet
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VLANs
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Range Type
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Usage
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0. 4095
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Reserved
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- For system use only.
- Cannot use these VLANs. |
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1
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Normal
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- Cisco default VLAN on a switch.
- Can be used this VLAN. - Cannot delete it. -All interfaces belong to this VLAN by default. |
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2 -1001
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Normal
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Used for Ethernet VLANs
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1002 - 1005
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Normal
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For Legacy reasons:
- are used for Token Ring and Fiber Distributed Data Interface (FDDI) VLANs. - Cannot delete VLANs 1002 - 1005 - stored in vlan.dat in flash memory and in running config if switch in transparent mode |
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1006 - 4094
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Extended
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Used for Ethernet VLANs
- Switch needs to be in transparent mode when creating extended VLANs important in VTP version 3 extended-range vlans are stored in VLAN database and can be propagated by VTP. + supports VLANs creation and and modification in server and transparent modes |
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If a VLAN is deleted, then the port associated to the vlan becomes inactive.
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Port becomes inactive if it is associate to a non-created VLAN
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The olde version of 802.1q(common encapsulation method todya) is ISL
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Native VLAN is used for backward compatibility, where untagged traffic is common
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VLAN 1 is the management VLAN (cannot be changed) ==> messages like cdp, stp, lldp are going to be carried over vlan 1.
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If on the connected switches there is a different native vlan, cdp will tell us there is a vlan mismatch
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Maximum number of VLANs might vary from one switch to the other depending on VTP, HSRP
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A group of devices that share a common broadcast domain
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Cisco proprietary Layer 2 messaging protocol.
Maintains VLAN configuration consistency (Manages VLAN addition, deletion, and renaming). Modes: - Client - Server - Client |
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Used by cisco switches to automatically negotiate whether an interface used between two switches should be put in access or trunk mode.
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Dynamic Auto forms a trunk only if it receives DTP messages
- Do not negotiate - Only listens |
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Dynamic Desirable will negociate the mode automatically and dynamically tries to to convert the link to trunk
- Generates DTP messages - Listens for incoming DTP messages |
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Dynamic auto
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Dynamic auto
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access
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Dynamic auto
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Dynamic desirable
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trunk
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Dynamic desirable
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Dynamic desirable
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trunk
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Dynamic auto or Dynamic desirable
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trunk
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trunk
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Dynamic auto or Dynamic desirable
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access
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access
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- Cisco proprietary protocol
- Exchange VLAN information - Synchronize vlan information (VLAN ID and name) with switches inside the same VTP domain |
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VTP Client mode can't exchange vlan configuration(cannot create or delete)
Receives VTP updates(processes them) and forwards them |
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VTP server mode can create and delete VLANs.
Propagates VLAN changes. Default mode for Cisco switches |
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VTP transparent mode does not share its VLAN database
Forwards received VTP advertisements Creates and deletes VLANs on a VTP transporant switch. |
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VTP mode off similar to VTP transparent mode but does not forward received updates
suported only in VTPv3 |
S1# conf t
S1(config)# vlan 2
S1(config-vlan)# name SalesVLAN004
S1# conf t
S1(config)# interface f 0/3
S1(config-if)# switchport mode access
S1(config-if)# switchport access vlan 2S1# conf t
S1(config)# vlan 3
S1(config-vlan)# name telephony
S1(config-vlan)# exit
S1(config)# interface f 0/2
S1(config-if)# switchport mode access
S1(config-if)# switchport voice vlan 3
SW1# show interfaces FastEthernet0/2 switchport
Name: Fa0/2
Switchport: Enabled
Administrative Mode: dynamic desirable
Operational Mode: static access
Administrative Trunking Encapsulation: negotiate
Operational Trunking Encapsulation: native
Negotiation of Trunking: On
Access Mode VLAN: 2 (data)
Trunking Native Mode VLAN: 1 (default)
Administrative Native VLAN tagging: enabled
Voice VLAN: 3 (telephony)
<... output omitted ...>
SW1# show vlan
VLAN Name Status Ports
---- -------------------------------- --------- -------------------------------
1 default active Fa0/1, Fa0/3, Fa0/4, Fa0/5, Fa0/6, Fa0/7
2 data active Fa0/2
3 telephony active Fa0/2
1002 fddi-default act/unsup
1003 token-ring-default act/unsup
1004 fddinet-default act/unsup
1005 trnet-default act/unsup
VLAN Type SAID MTU Parent RingNo BridgeNo Stp BrdgMode Trans1 Trans2
---- ----- ---------- ----- ------ ------ -------- ---- -------- ------ ------
1 enet 100001 1500 - - - - - 0 0
2 enet 100002 1500 - - - - - 0 0
3 enet 100003 1500 - - - - - 0 0
1002 fddi 101002 1500 - - - - - 0 0
1003 tr 101003 1500 - - - - - 0 0
1004 fdnet 101004 1500 - - - ieee - 0 0
1005 trnet 101005 1500 - - - ibm - 0 0
Remote SPAN VLANs
------------------------------------------------------------------------------
Primary Secondary Type Ports
------- --------- ----------------- ------------------------------------------
SW1# show vlan id 2
VLAN Name Status Ports
---- -------------------- ------- ---------------------
2 data active Fa0/2
VLAN Type SAID MTU Parent RingNo BridgeNo Stp BrdgMode Trans1 Trans2
---- ---- ------- ----- ------ ------ -------- --- --------- ------ ------
2 enet 100002 1500 - - - - - 0 0
<... output omitted ...>
SW1# show vlan brief
VLAN Name Status Ports
---- -------------------------------- --------- -------------------------------
1 default active Fa0/1, Fa0/3, Fa0/4, Fa0/5, Fa0/6, Fa0/7
2 data active Fa0/2
3 telephony active Fa0/2
1002 fddi-default act/unsup
1003 token-ring-default act/unsup
1004 fddinet-default act/unsup
1005 trnet-default act/unsup
Switch# show mac address-table
Mac Address Table
-------------------------------------------
Vlan Mac Address Type Ports
---- ----------- -------- -----
1 aabb.cc00.2f00 DYNAMIC Fa0/0
1 aabb.cc00.3100 DYNAMIC Fa0/1
2 aabb.cc00.3000 DYNAMIC Fa0/2Switch# show interfaces Ethernet0/1 switchport
Name: Et0/1
Switchport: Enabled
Administrative Mode: static access
Operational Mode: static access
Administrative Trunking Encapsulation: dot1q
Operational Trunking Encapsulation: native
Negotiation of Trunking: Off
Access Mode VLAN: 10 (Inactive)
Trunking Native Mode VLAN: 1 (default)
Administrative Native VLAN tagging: enabled
Voice VLAN: noneS1# conf t
S1(config)# interface e 0/0
S1(config-if)# switchport mode trunk
S1(config-if)# switchport trunk native vlan 99
S1(config-if)# switchport trunk allowed vlan 10, 20, 30S1(config-if)# switchport trunk allowed vlan 10, 20, 30, 100S1(config-if)# switchport trunk allowed vlan 100SwitchX# show interfaces Ethernet0/0 switchport
Name: Et0/0
Switchport: Enabled
Administrative Mode: trunk
Operational Mode: trunk
Administrative Trunking Encapsulation: dot1q
Operational Trunking Encapsulation: dot1q
Negotiation of Trunking: On
Access Mode VLAN: 1 (default)
Trunking Native Mode VLAN: 99 (VLAN0099)
Administrative Native VLAN tagging: enabled
Voice VLAN: none
<... output omitted ...>
Trunking VLANs Enabled: 10,20,30,99
<... output omitted ...>Switch# show interfaces trunk
Port Mode Encapsulation Status Native vlan
Et0/0 on 802.1q trunking 99
Port Vlans allowed on trunk
Et0/0 10,20,30,99
Port Vlans allowed and active in management domain
Et0/0 10,20,30,99
<... output omitted ...>SwitchX# show interfaces status
Port Name Status Vlan Duplex Speed Type
Et0/0 connected trunk auto auto unknown
Et0/1 connected 2 auto auto unknown
Et0/2 connected 1 auto auto unknown
Et0/3 connected 1 auto auto unknownSW1# configure terminal
SW1(config)# interface Ethernet0/0
SW1(config-if)# switchport mode trunk
SW1(config-if)# switchport trunk native vlan 90
SW1(config-if)# switchport trunk native vlan tagSW1(config-if)# switchport trunk native vlan tagNo comments yet.
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