1. Purpose:
The purpose of this chapter is to describe VLAN operations on the Catalyst
switches.
Timing:
This module should take about two hours to present.
Contents:
Basic VLAN operations.
VTP operations.
Cat1900 VLAN configurations.
Lab first part - VLAN configurations.
Lab second part - STP.

2. Objectives
Upon completion of this chapter, you will be able to perform the following tasks:
Configure a VLAN
Configure VLAN Trunking Protocol (VTP)
Configure a switch for trunking
Verify VLAN connectivity
Verify spanning-tree operations
Slide 1 of 1
Purpose:
Emphasize:

3. A VLAN = A broadcast domain = Logical network (subnet)
VLAN Overview
Segmentation
Flexibility
Security
3rd floor
2nd floor
Slide 1 of 1
Purpose:
Emphasize: A VLAN is a broadcast domain.
Note: In order to have inter-vlan communications, a router is required.
1st floor
SALES HR
ENG
A VLAN = A broadcast domain = Logical network (subnet)

4. VLAN Operations Each logical VLAN is like a separate physical bridge
Switch A
Green
VLAN
Black
Red
Slide 1 of 3
Purpose:
Emphasize:
Each port on the switch can be assigned to a VLAN.
By default, all ports are in VLAN 1, a factory default VLAN.
Each logical VLAN is like a separate physical bridge

5. VLAN Operations Each logical VLAN is like a separate physical bridge
Switch A
Green
VLAN
Black
Red
Switch B
Slide 2 of 3
Purpose:
Emphasize:
To allow VLANs to span across multiple switches, the connection between the switches must belong to mulitple VLANs.
Red
VLAN
Black
VLAN
Green
VLAN
Each logical VLAN is like a separate physical bridge
VLANs can span across multiple switches

6. VLAN Operations Each logical VLAN is like a separate physical bridge
Switch A
Green
VLAN
Black
Red
Switch B
Trunk
Fast Ethernet
Slide 3 of 3
Purpose:
Emphasize:
A trunk is used to connect two switches together.
A trunk carries traffic for multiple VLANs.
Only the fastethernet ports on the 1900 can be configured as trunk port.
Trunking is off by default on the 1900 fastethernet ports (fa 0/26 and fa 0/27).
Note:
The 1900 supports DISL.
At the time of the beta, the core switch (2900xl) doesn’t support DISL.
Red
VLAN
Black
VLAN
Green
VLAN
Each logical VLAN is like a separate physical bridge
VLANs can span across multiple switches
Trunks carries traffic for multiple VLANs

7. VLAN Membership Modes Static VLAN Dynamic VLAN Port e0/4 Port e0/9
Trunk
Port e0/4
Port e0/9
VLAN5
Slide 1 of 1
Purpose:
Emphasize:
Note:
Once a port has been assigned to a VLAN, it can not send or receive traffic from devices in another VLAN without the intervention of a layer 3 device like a router.
The 1900 can’t be configure as the VMPS.
A CiscoWorks 2000 or CWSI management station or a Cat 5000 switch can be configured as the VMPS.
In the future, dynamic VLANs may also offer membership based on other criteria such as protocol or application. Dynamic VLANs are covered in the Managing Cisco Switched Internetworks class.
VLAN10
VMPS
= vlan 10
MAC =

8. ISL Tagging ISL trunks enable VLANs across a backbone
Performed with ASIC
Not intrusive to client stations, client does not see the ISL header
Effective between switches, routers and switches, switches and servers with ISL network interface cards
VLAN Tag added by incoming port
Inter-Switch Link carries VLAN identifier
Slide 1 of 1
Purpose:
Emphasize:
Note:
The 1900 only supports ISL trunking.
ISL is Cisco Proprietary Q is an IEEE standard.
Other trunk types:
LANE (VLANSs over ATM)
(FDDI trunk)
VLAN Tag stripped by forwarding port

9. Encapsulated Ethernet frame
ISL Encapsulation
ISL Header
26 bytes
Encapsulated Ethernet frame
CRC
4 bytes DA
Type
User SA
LEN
AAAA03
HSA
VLAN
BPDU
BPDU
INDEX
RES
VLAN
BPDU
Slide 1 of 1
Purpose:
Emphasize:
Note:
Since ISL technology is implemented in ASICs, frames are tagged at wire speed.
The number of VLANs supported by a switch depends on the switch hardware.
The Catalyst 1900en supports 64 active VLANs with an instance of STP per VLAN.
PVST = Per VLAN Spanning Tree. PVST is a Cisco proprietary implementation. It requires Cisco ISL encapsulation in order to work.
Frames encapsulated with ISL header and CRC
Support for many VLANs (1024)
VLAN field
BPDU bit

10. VLAN Trunking Protocol (VTP)
A messaging system that advertises VLAN configuration information
Maintains VLAN configuration consistency throughout a common administrative domain
VTP sends advertisements on trunk ports only
Support mixed media trunks (Fast Ethernet, FDDI, ATM)
VTP Domain “ICND”
3.Sync to the latest vlan information
Slide 1 of 1
Purpose:
Emphasize:
Notes: VTP is a Cisco proprietray feature. VTP is a Layer 2 messaging protocol that maintains VLAN configuration consistency by managing the addition, deletion, and renaming of VLANs on a network-wide basis. VTP minimizes misconfigurations and configuration inconsistencies that can cause several problems, such as duplicate VLAN names, incorrect VLAN-type specifications, and security violations. A VTP domain (also called a VLAN management domain) is one switch or several interconnected switches sharing the same VTP domain. A switch is configured to be in only one VTP domain. You make global VLAN configuration changes for the domain by using the Cisco IOS command-line interface (CLI), Cisco Visual Switch Manager Software, or Simple Network Management Protocol (SNMP). By default, a 1900 switch is in the no-management-domain state until it receives an advertisement for a domain over a trunk link or you configure a management domain. The default VTP mode is server mode, but VLANs are not propagated over the network until a management domain name is specified or learned. If the switch receives a VTP advertisement over a trunk link, it inherits the management domain name and configuration revision number. The switch then ignores advertisements with a different management domain name or an earlier configuration revision number. When you make a change to the VLAN configuration on a VTP server, the change is propagated to all switches in the VTP domain. VTP advertisements are transmitted out all trunk connections, including Inter-Switch Link (ISL), IEEE Q, IEEE , and ATM LAN Emulation (LANE). If you configure a switch from VTP transparent mode, you can create and modify VLANs, but the changes are not transmitted to other switches in the domain, and they affect only the individual switch. 2
1.“new vlan added”

11. VTP Modes Server Client Transparent Create vlans Modify vlans
Delete vlans
Sends/forwards advertisements
Synchronize
Saved in NVRAM
Server
Sends/forwards advertisements
Synchronize
Not saved in NVRAM
Slide 1 of 1
Purpose:
Emphasize:
Default VTP mode on the Catalyst switches is Server. Be careful when adding new switches into an existing network. This is covered in more detail later.
Create vlans
Modify vlans
Delete vlans
Forwards advertisements
Does not synchronize
Saved in NVRAM
Client
Transparent

12. How VTP Works VTP advertisements are sent as multicast frames
VTP servers and clients synchronized to latest revision number
VTP advertisement are sent every five minutes or when there is a change
Slide 1 of 2
Purpose:
Emphasize:
Notes:
VTP advertisements are sent on factory-default VLAN based on the media type.
Each advertisement starts as configuration revision number 0. When changes are made, the configuration revision number increments (n+1).
Routers ignore VTP packets.
There are two types of advertisements; requests from clients that want to learn at boot up and response from servers.
There are three types of messages; summary advertisements sent every 300 seconds on VLAN 1, subset advertisements with information about VLANs, and advertisement requests from clients where the server responds with summary and subset advertisements

13. How VTP Works VTP advertisements are sent as multicast frames
VTP servers and clients synchronized to latest revision number
VTP advertisement are sent every five minutes or when there is a change
1.Add new VLAN
2.Rev 3 --> Rev 4
Slide 2 of 2
Purpose:
Emphasize: The latest revision number is what the switches will synchronize to. 3
Server 3
4.Rev 3 --> Rev 4
5.Sync new vlan info
4.Rev 3 --> Rev 4
5.Sync new vlan info
Client
Client

14. VTP Pruning
Increases available bandwidth by reducing unnecessary flooded traffic
Example: Station A sends broadcast, broadcast is only flooded toward any switch with ports assigned to the red VLAN
Port 2 B
Switch 4
Flooded traffic is pruned
Switch 2
Slide 1 of 1
Purpose:
Emphasize: VTP prunning provides optimized flooding. Without VTP prunning, station A’s broadcast will be flooded to all switches whether they have any port in the red vlan or not.
Note:
VLAN 1 can’t be prunned. STP, CDP, VTP updates are sent on VLAN1.
All switches in the switched network must support prunning or prunning will be disabled.
Each trunk port maintains a state variable per vlan indicating if the switch has any port assigned to a particular vlan or not.
Red VLAN
Switch 5
Port 1 A
Switch 6
Switch 3
Switch 1

15. VLAN Configuration Guidelines
Maximum number of VLANs is switch-dependent
Catalyst 1900 supports 64 VLANs with a separate spanning tree per VLAN
VLAN1 is One of the factory default VLANs
CDP and VTP advertisements are sent on VLAN1
Catalyst 1900 IP address is in the VLAN1 broadcast domain
Must be in VTP server or transparent mode to create, add, or delete VLANs
Slide 1 of 1
Purpose:
Emphasize:
Note:
In the ICND lab,
All the switches and routers are in VLAN1.
The core server and the core router are in multiple VLANs.
Each workgroup PC is on an unique VLAN.

16. VLAN Configuration Steps
Enable VTP (optional)
Enable trunking
Create VLANs
Assign VLAN to ports
Slide 1 of 1
Purpose: Show the four basic steps for configuring VLANs.
Emphasize:

17. VTP Configuration Guidelines
VTP domain name
VTP mode (server/client/transparent)—VTP server mode is the default
VTP pruning
VTP password
VTP trap
Slide 1 of 1
Purpose:
Emphasize:
Notes:
All switches in a VTP domain must run the same VTP version.
The password entered with a domain name should be the same for all switches in the domain. If you configure a VTP password, the management domain will not function properly if you do not assign the management domain password to each switch in the domain.
A VTP version 2-capable switch can operate in the same VTP domain as a switch running VTP version 1 provided version 2 is disabled on the version 2-capable switch (version 2 is disabled by default).
Do not enable VTP version 2 on a switch unless all of the switches in the same VTP domain are version 2-capable. When you enable version 2 on a switch, all of the version 2-capable switches in the domain must have version 2 enabled. If there is a version 1-only switch, it will not exchange VTP information with switches with version 2 enabled.
If there are token ring networks in your environment, you must enable VTP version 2 for Token Ring VLAN switching to function properly.
Enabling or disabling VTP pruning on a VTP server enables or disables VTP pruning for the entire management domain.
In the lab, all the switches are set to VTP transparent mode.
Use caution when adding a new switch into an existing domain. A new switch should be added in client mode to prevent the new switch from propagating incorrect VLANs information
Use the delete vtp command to reset the VTP revision number

18. Creating a VTP Domain wg_sw_a(config)#
vtp [server | transparent] [domain domain-name] [trap {enable | disable}]
[password password] [pruning {enable | disable}
Slide 1 of 2
Purpose:
Emphasize:

19. Creating a VTP Domain wg_sw_a(config)# wg_sw_a#conf terminal
vtp [server | transparent] [domain domain-name] [trap {enable | disable}]
[password password] [pruning {enable | disable}
wg_sw_a#conf terminal
Enter configuration commands, one per line. End with CNTL/Z
wg_sw_a(config)#vtp transparent
wg_sw_a(config)#vtp domain switchlab
Slide 2 of 2
Purpose:
Emphasize:
Note:
The two commands shown in the slide can also be combined into one command:
“vtp domain switchlab transparent”

20. Verifying VTP Configurations
wg_sw_a#show vtp
Slide 1 of 2
Purpose:
Emphasize:

21. Verifying VTP Configurations
wg_sw_a#show vtp
wg_sw_a#show vtp
VTP version: 1
Configuration revision: 4
Maximum VLANs supported locally: 1005
Number of existing VLANs: 6
VTP domain name : switchlab
VTP password :
VTP operating mode : Transparent
VTP pruning mode : Enabled
VTP traps generation : Enabled
Configuration last modified by: at :00:00
Slide 2 of 2
Purpose:
Emphasize:
Note:
In the slide, the VLAN database was last modified locally. The IP address of wg_sw_a is
In the lab, the 1900s are running version , prunning was disabled by default. In the documentation, prunning is suppose to be enabled by default.

22. trunk [on | off | desirable | auto | nonegotiate]
Defining a Trunk
wg_sw_a(config-if)#
trunk [on | off | desirable | auto | nonegotiate]
On = Set trunk on and negotiate with other side
Off = Set trunk off and negotiate with other side
Desirable = Negotiate with other side. Trunk on if other side is on, desirable, or auto
Auto = Will be a trunk only if the other side is on or desirable
Non-negotiate = Set trunk on and will not negotiate
Slide 1 of 2
Purpose:
Emphasize: The 1900 supports DISL.
Note:
At the time of the beta, the core switch (2900xl) does not support DISL.
If trunking is on at one end, and off at the other end, the link will be down.

23. Defining a Trunk wg_sw_a(config-if)# First trunk port(Port A)
trunk [on | off | desirable | auto | nonegotiate]
On = Set trunk on and negotiate with other side
Off = Set trunk off and negotiate with other side
Desirable = Negotiate with other side. Trunk on if other side is on, desirable, or auto
Auto = Will be a trunk only if the other side is on or desirable
Non-negotiate = Set trunk on and will not negotiate
Slide 2 of 2
Purpose:
Emphasize:
Note:
wg_sw_a#conf terminal
Enter configuration commands, one per line. End with CNTL/Z
wg_sw_a(config)#interface f0/26
wg_sw_a(config-if)#trunk on
First trunk port(Port A)

24. Verifying a Trunk wg_sw_a#show trunk [A | B] Slide 1 of 2 Purpose:
Emphasize:
Trunk A = fasthethernet 0/26
Trunk B = fastetherent 0/27

25. Verifying a Trunk wg_sw_a#show trunk [A | B] wg_sw_a#show trunk a
DISL state: On, Trunking: On, Encapsulation type: ISL
Slide 2 of 2
Purpose:
Emphasize:
Note: The Cat 1900,at the time of the beta, only supports ISL trunking. It does not support 802.1Q trunking.

26. vlan vlan# [name vlan-name]
Adding a VLAN
wg_sw_a(config)#
vlan vlan# [name vlan-name]
Slide 1 of 2
Purpose:
Emphasize:
Each VLAN has a unique, four-digit number that can be from 1 to To add a VLAN to the VLAN database, the minimum parameter required is the VLAN number.

27. vlan vlan# [name vlan-name]
Adding a VLAN
wg_sw_a(config)#
vlan vlan# [name vlan-name]
wg_sw_a#conf terminal
Enter configuration commands, one per line. End with CNTL/Z
wg_sw_a(config)#vlan 9 name switchlab2
Slide 2 of 2
Purpose:
Emphasize:

28. wg_sw_a#show vlan [vlan#]
Verifying a VLAN
wg_sw_a#show vlan [vlan#]
Slide 1 of 2
Purpose:
Emphasize:

29. wg_sw_a#show vlan [vlan#]
Verifying a VLAN
wg_sw_a#show vlan [vlan#]
wg_sw_a#sh vlan 9
VLAN Name Status Ports
9 switchlab Enabled
VLAN Type SAID MTU Parent RingNo BridgeNo Stp Trans1 Trans2
9 Ethernet Unkn
Slide 2 of 2
Purpose:
Emphasize:
Note:
Type: Default is ethernet. (other types are FDDI and Token Ring)
SAID: Is used for FDDI trunking.
MTU: Default is 1500 for ethernet vlan.
STP: The 1900 only supports 802.1d STP. It does not support DEC or IBM STP. Routers support all three STP standards.
Other parameters: Used for Token Ring or FDDI VLANs.

30. vlan vlan# name vlan-name
Modifying a VLAN Name
wg_sw_a(config)#
vlan vlan# name vlan-name
wg_sw_a#conf terminal
Enter configuration commands, one per line. End with CNTL/Z
wg_sw_a(config)#vlan 9 name switchlab90
Slide 1 of 1
Purpose:
Emphasize:
Note: The output shows that there are currently no ports assigned to VLAN 9.
wg_sw_a#show vlan 9
VLAN Name Status Ports
9 switchlab Enabled

31. Assigning Switch Ports to a VLAN
wg_sw_a(config-if)#
vlan-membership {static {vlan#} | dynamic}
Slide 1 of 2
Purpose:
Emphasize: By default, all ports are in VLAN 1.

32. Assigning Switch Ports to a VLAN
wg_sw_a(config-if)#
vlan-membership {static {vlan#} | dynamic}
wg_sw_a#conf terminal
Enter configuration commands, one per line. End with CNTL/Z
wg_sw_a(config)#interface ethernet 0/8
wg_sw_a(config-if)#vlan-membership static 9
Slide 2 of 2
Purpose:
Emphasize:
Note:
In the lab, we will only be configuring static VLAN membership.

33. Verifying VLAN Membership
wg_sw_a#show vlan-membership
Slide 1 of 2
Purpose:
Emphasize:

34. Verifying VLAN Membership
wg_sw_a#show vlan-membership
wg_sw_a#show vlan-membership
Port VLAN Membership Type Port VLAN Membership Type
Static Static
Static Static
Static Static
Static Static
Static Static
Static Static
Static Static
Static Static
Slide 2 of 2
Purpose:
Emphasize: Port 1 = e0/1, ……. AUI = e0/25, A = fa 0/26, B = fa 0/27
Note: port 1=e0/1, port 2=e0/

35. Verifying Spanning Tree
wg_sw_a#show spantree {vlan number}
Slide 1 of 2
Purpose:
Emphasize:
This command displays all instances of spanning-tree that are currently running. If you specify a particular vlan, the system just display the spanning-tree operating parameters for the specified VLAN.
Spanning tree is enabled by default on all VLANs.
Use the following global configuration command to disable Spanning tree for a VLAN:
wg_sw_a(config)#no spantree 2
wg_sw_a#sh span 2
Error: STP is not enabled for VLAN 2
Note:
The command syntax on the 2900xl is a little different:
“show spanning-tree vlan {vlan number}”.
One of the lab procedure requires the students to telnet to the core switches (2900xl) to examine the STP status.

36. Verifying Spanning Tree
wg_sw_a#show spantree {vlan number}
wg_sw_a#show spantree 1
VLAN1 is executing the IEEE compatible Spanning Tree Protocol
Bridge Identifier has priority 32768, address 0050.F037.DA00
Configured hello time 2, max age 20, forward delay 15
Current root has priority 0, address 00D0.588F.B600
Root port is FastEthernet 0/26, cost of root path is 10
Topology change flag not set, detected flag not set
Topology changes 53, last topology change occured 0d00h17m14s ago
Times: hold 1, topology change 8960
hello 2, max age 20, forward delay 15
Timers: hello 2, topology change 35, notification 2
Port Ethernet 0/1 of VLAN1 is Forwarding
Port path cost 100, Port priority 128
Designated root has priority 0, address 00D0.588F.B600
Designated bridge has priority 32768, address 0050.F037.DA00
Designated port is Ethernet 0/1, path cost 10
Timers: message age 20, forward delay 15, hold 1
Slide 2 of 2
Purpose:
Emphasize:
Note:
To adjust the STP timers or bridge priority on the 1900, use the following global configuration command:
wg_sw_a(config)#spantree-template 1 ?
forwarding-time Set a Spanning Tree FORWARD Interval
hello-time Set a Spanning Tree HELLO Interval
max-age Set a Spanning Tree MAX AGE Interval
priority Set a Spanning Tree PRIORITY
vlan Assign up to ten VLANs to a bridge template
On the 1900, you can assign up to 4 spantree-templates then you can assign VLANs to each template. When you modify a template, you are modifying all the VLANs belonging to that template.

37. Visual Objective ... SUBNET VLAN POD
wg_ro_x, wg_sw_x, core_sw_a
wg_pc_a, core_server
wg_pc_b, core_server
wg_pc_c, core_server
wg_pc_d, core_server
wg_pc_e, core_server
wg_pc_f, core_server
wg_pc_g, core_server
wg_pc_h, core_server
wg_pc_i, core_server
wg_pc_j, core_server
wg_pc_k, core_server
wg_pc_l, core_server
wg_pc_a
VLAN2
fa0/26
(port A)
e0/1
e0/2 e0
wg_sw_a
wg_ro_a
wg_pc_l
VLAN13
fa0/26
(port A)
e0/1
Slide 1 of 1
Purpose:
Emphasize:
Notes: Refer to the lab setup guide for lab instructions.
e0/2 e0
wg_ro_l
wg_sw_l
ISL
...
ISL
fa0/1
fa0/12
fa0/24
core_ server
10.x.x.1
ISL
core_sw_a

38. Visual Objective ... ... wg_pc_a 10.2.2.12 VLAN2 SUBNET VLAN POD
wg_ro_x, wg_sw_x, core_sw_a, core_sw_b
wg_pc_a, core_server
wg_pc_b, core_server
wg_pc_c, core_server
wg_pc_d, core_server
wg_pc_e, core_server
wg_pc_f, core_server
wg_pc_g, core_server
wg_pc_h, core_server
wg_pc_i, core_server
wg_pc_j, core_server
wg_pc_k, core_server
wg_pc_l, core_server
fa0/26
(port A)
fa0/27
(port B)
e0/1
wg_sw_a
wg_pc_l
VLAN13
Slide 1 of 1
Purpose:
Emphasize:
Notes: Refer to the lab setup guide for lab instructions.
fa0/26
(port A)
fa0/27
(port B)
e0/1
wg_sw_l
...
...
ISL
ISL
ISL
ISL
fa0/12
fa0/12
fa0/1
fa0/1
fa0/13
fa0/13
fa0/24
ISL
core_ server
fa0/14
ISL
fa0/14
core_sw_a
core_sw_b
10.x.x.1

39. Summary
After completing this chapter, you should be able to perform the following tasks:
Configuring VLAN
Configuring VTP
Configuring a trunk
Verifing Spanning Tree Operations
Slide 1 of 1
Purpose:
Emphasize:

40. Review Questions 1. What are the three VTP modes?
2. Over what type of port can VTP advertisements be sent?
3. VLAN ID is carried in the ________ header.
4. How do we assign a VLAN to a port?
Slide 1 of 1
Purpose:
Emphasize:
Notes: Refer to the appendix for answer to the review questions.