1. Extending Switched Networks with Virtual LANs
Configuring VLANs

2. Outline Overview VTP Configuration 802.1Q Trunking Configuration
ISL Trunking Configuration
VLAN Creation
VLAN Name Modification
VLAN Port Assignment
VLAN Configuration Verification
Adds, Moves, and Changes for VLANs
VLAN Troubleshooting
Summary
Slide 1 of 2
Purpose: This slide states the chapter objectives.
Emphasize: Read or state each objective so that each student has a clear understanding of the chapter objectives.
Note: Catalyst switches have different CLIs. The Catalyst 2900xl and the Catalyst 1900 has a Cisco IOS CLI. The Cisco IOS CLI commands available on the 2900xl is different from the The Catalyst 5000 family has no Cisco IOS CLI, and use the set commands instead. This class only covers the configuration on the Catalyst 1900 switch.

3. VTP Configuration Guidelines
VTP domain name
VTP mode (server, client, or transparent); server mode is default
VTP pruning
VTP password
VTP version
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 to an existing domain. Add a new switch in client mode to prevent the new switch from propagating incorrect VLAN information.
Reset the VTP revision number to 0, but change the VTP mode to transparent.

4. Creating a VTP Domain Catalyst 2950 Series
wg_sw_2950# configure terminal
wg_sw_2950(config)# vtp mode [ server | client | transparent ]
wg_sw_2950(config)# vtp domain domain-name
wg_sw_2950(config)# vtp password password
wg_sw_2950(config)# vtp pruning
wg_sw_2950(config)# end
Layer 2 of 2
Note: The two commands shown in the slide can also be combined into one command:
vtp domain switchlab transparent

5. VTP Configuration Example
Switch(config)# vtp domain ICND
Changing VTP domain name to ICND
Switch(config)# vtp mode transparent
Setting device to VTP TRANSPARENT mode.
Switch(config)# end
Switch#show vtp status
VTP Version : 2
Configuration Revision : 0
Maximum VLANs supported locally : 64
Number of existing VLANs : 17
VTP Operating Mode : Transparent
VTP Domain Name : ICND
VTP Pruning Mode : Disabled
VTP V2 Mode : Disabled
VTP Traps Generation : Disabled
MD5 digest : 0x7D 0x6E 0x5E 0x3D 0xAF 0xA0 0x2F 0xAA
Configuration last modified by at :08:05
Switch#

6. 802.1Q Trunking Issues
Make sure that the native VLAN for an 802.1Q trunk is the same on both ends of the trunk link.
Make sure that your network is loop-free before disabling STP.
Note that native VLAN frames are untagged.

7. Configuring 802.1Q Trunking
wg_sw_a(config-if)# switchport mode trunk
Configures the port as a VLAN trunk
Note: The Catalyst 2950 series switches support only 802.1Q encapsulation.

8. Configuring ISL Trunking
wg_sw_4000(config)# interface {fastethernet | gigabitethernet} slot/port
Select the interface to configure.
wg_sw_4000(config-if)# shutdown
(Optional) Shut down the interface to prevent traffic flow until configuration is complete.
wg_sw_4000(config-if)# switchport trunk encapsulation {isl | dot1q | negotiate}
(Optional) Specify the encapsulation. Note: You must enter this command with either the isl or dot1q keyword to support the switchport mode trunk command, which is not supported by the default mode (negotiate).
Layer 2 of 2
wg_sw_4000(config-if)# switchport mode {dynamic {auto | desirable} | trunk}
Configure the interface as a Layer 2 trunk (required only if the interface is a Layer 2 access port or to specify the trunking mode).

9. Configuring ISL Trunking (Cont.)
wg_sw_4000# configure terminal
wg_sw_4000(config-if)# interface gigabitEthernet 2/24
wg_sw_4000(config-if)# shutdown
wg_sw_4000(config-if)# switchport trunk encapsulation isl
wg_sw_4000(config-if)# switchport mode trunk
wg_sw_4000(config-if)# no shutdown
Layer 2 of 2
Note: Not all Catalyst series switches support ISL encapsulation.

10. VLAN Creation Guidelines
The maximum number of VLANs is switch-dependent.
Most Catalyst desktop switches support 64 VLANs with a separate spanning tree per VLAN.
VLAN 1 is the factory default Ethernet VLAN.
CDP and VTP advertisements are sent on VLAN 1.
The Catalyst switch IP address is in the management VLAN (VLAN 1 by default).
To add or delete VLANs, the switch must be in VTP server or transparent mode.
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.

11. Adding a VLAN Catalyst 2950 Series Switch# configure terminal
Switch(config)# vlan 2
Switch(config-vlan)# name VLAN2
Layer 2 of 2

12. wg_sw_a(config-vlan)# name vlan-name
Modifying a VLAN Name
wg_sw_a(config-vlan)# name vlan-name
wg_sw_a# configure terminal
wg_sw_a(config)# vlan 2
wg_sw_a(config-vlan)# name switchlab2
Note: The output shows that there are currently no ports assigned to VLAN9.

13. Assigning Switch Ports to a VLAN
Catalyst 2950 Series
wg_sw_2950(config-if)# switchport access [vlan vlan# | dynamic]
wg-sw_2950# configure terminal
wg_sw_2950(config)# interface fastethernet 0/2
wg_sw_2950(config-if)# switchport access vlan 2
wg_sw_2950# show vlan
VLAN Name Status Ports
default active Fa0/1, Fa0/3, Fa0/4
2 vlan active Fa0/2
Layer 2 of 2
Note: In the lab, we will only be configuring static VLAN membership.

14. Verifying the VTP Configuration
wg_sw_2950# show vtp status
wg_sw_2950# show vtp status
VTP Version : 2
Configuration Revision : 0
Maximum VLANs supported locally : 64
Number of existing VLANs : 17
VTP Operating Mode : Server
VTP Domain Name : ICND_lab
VTP Pruning Mode : Disabled
VTP V2 Mode : Disabled
VTP Traps Generation : Disabled
MD5 digest : 0x7D 0x6E 0x5E 0x3D 0xAF 0xA0 0x2F 0xAA
Configuration last modified by at :08:05
Layer 2 of 2
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 , and pruning was disabled by default. In the documentation, pruning is suppose to be enabled by default.

15. wg_sw_2950# show interfaces interface [switchport | trunk]
Verifying a Trunk
wg_sw_2950# show interfaces interface [switchport | trunk]
wg_sw_2950# show interfaces fa0/11 switchport
Name: Fa0/11
Switchport: Enabled
Administrative Mode: trunk
Operational Mode: down
Administrative Trunking Encapsulation: dot1q
Negotiation of Trunking: On
Access Mode VLAN: 1 (default)
Trunking Native Mode VLAN: 1 (default)
. . .
Layer 2 of 2
Note: The Catalyst 1900,at the time of the beta, only supports ISL trunking. It does not support 802.1Q trunking.
wg_sw_2950# show interfaces fa0/11 trunk
Port Mode Encapsulation Status Native vlan
Fa0/ desirable q trunking
Port Vlans allowed on trunk
Fa0/
Port Vlans allowed and active in management domain
Fa0/

16. wg_sw_2950# show vlan [brief | id vlan-id || name vlan-name]
Verifying a VLAN
Catalyst 2950 Series
wg_sw_2950# show vlan [brief | id vlan-id || name vlan-name]
wg_sw_2950# show vlan id 2
VLAN Name Status Ports
2 switchlab active Fa0/2, Fa0/12
VLAN Type SAID MTU Parent RingNo BridgeNo Stp BrdgMode Trans1 Trans2
2 enet
wg_sw_2950#
Layer 2 of 2
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 Spanning-Tree Protocol. It does not support DEC or IBM Spanning-Tree Protocol. Routers support all three Spanning-Tree Protocol standards.
Other parameters: Used for Token Ring or FDDI VLANs.

17. Verifying VLAN Membership
wg_sw_2950# show vlan brief
wg_sw_2950# show vlan brief
VLAN Name Status Ports
1 default active Fa0/1, Fa0/2, Fa0/3, Fa0/4
2 vlan active
3 vlan active
4 vlan active
1002 fddi-default act/unsup
1003 token-ring-default act/unsup
1004 fddinet-default act/unsup
1005 trnet-default act/unsup
Layer 2 of 2
Emphasize: Port 1 = e0/1, ……. AUI = e0/25, A = fa 0/26, B = fa 0/27
wg_sw_2950# show interfaces interface switchport

18. Verifying STP for a VLAN
wg_sw_2950# show spanning-tree [active | detail | vlan vlan-id | summary]
wg_sw_2950# show spanning-tree vlan 2
VLAN0002
Spanning tree enabled protocol ieee
Root ID Priority 2
Address fc.a840
Cost
Port (FastEthernet0/12)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority (priority sys-id-ext 2)
Address a445.9b40
Aging Time 300
Interface Role Sts Cost Prio.Nbr Type
Fa0/ Desg FWD Shr
Fa0/ Root FWD P2p
Layer 2 of 2
Note: To adjust the spanning tree 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 four spanning tree templates, then you can assign VLANs to each template. When you modify a template, you are modifying all the VLANs belonging to that template.

19. Executing Adds, Moves, and Changes for VLANs
wg_sw_a(config)# vlan vlan-id
wg_sw_a(config-vlan)#
Enters the privileged EXEC VLAN configuration mode
Writes VLAN adds, moves, and changes to the vlan.dat file
wg_sw_a(config-if)# switchport access vlan vlan#
Purpose: This slide discuss the initial configurations on the routers and switches.
Note: There is no setup mode on the Catalyst 1900 switch.
Statically assigns a VLAN to a specific port

20. Troubleshooting Switched LANs

21. Problem: One Device Cannot Communicate with Another
Make sure that the IP address, subnet mask, and VLAN membership of the switch interface are correct.
If the host is in the same subnet as the switch interface, make sure that the switch interface and the switch port to which the host is connected are assigned to the same VLAN.
If the host is in a different subnet, make sure that the default gateway on the switch is configured with the address of a router that is in the same subnet as the switch interface.

22. Problem: One Device Cannot Communicate with Another (Cont.)
If the port is in listening or learning mode, wait until the port is in forwarding mode and try to connect to the host again.
Make sure that the speed and duplex settings on the host and the appropriate switch ports are correct.
If the connected device is an end station, enable spanning-tree PortFast and disable trunking on the port.
Make sure that the switch is learning the MAC address of the host.

23. Problem: A Device Cannot Establish a Connection Across a Trunk Link
Make sure that the trunking mode that is configured on both ends of the link is valid. The trunking mode should be “on” or “desirable” on one end and “on,” “desirable,” or “auto” on the other end.
Make sure that the trunk encapsulation type that is configured on both ends of the link is valid.
On IEEE 802.1Q trunks, make sure that the native VLAN is the same on both ends of the trunk.

24. Problem: VTP Not Updating Configuration on Other Switches
Make sure that the switches are connected through trunk links. VTP updates are exchanged only over trunk links.
Make sure that the VTP domain name is the same on the appropriate switches. VTP updates are exchanged only between switches in the same VTP domain.
Check to see if the switch is in VTP transparent mode. Only switches in VTP server or VTP client mode update their VLAN configuration based on VTP updates from other switches.
If you are using VTP passwords, you must configure the same password on all switches in the VTP domain.

25. Summary
When creating VLANs, you must decide whether to use VTP in your network. With VTP, you can make configuration changes centrally on one or more switches and have those changes automatically communicated to all the other switches in the same VTP domain.
The IEEE 802.1Q protocol carries traffic for multiple VLANs over a single link on a multivendor network. Use the switchport mode interface configuration command to set a Fast Ethernet or Gigabit Ethernet port to trunk mode.
The ISL protocol operates in a point-to-point environment to carry traffic for multiple VLANs over a single link. ISL is a Cisco proprietary protocol. On switches that support ISL, such as the Catalyst 4000, use the switchport trunk encapsulation interface configuration command to set a port to encapsulate with ISL.
Purpose: This slide discuss the initial configurations on the routers and switches.
Note: There is no setup mode on the Catalyst 1900 switch.

26. Summary (Cont.)
Catalyst switches have a factory default configuration in which various default VLANs are preconfigured to support various media and protocol types. The vlan global configuration command can be used to create a VLAN.
An existing VLAN name or number can be modified using the vlan global configuration command syntax.
After creating a VLAN, a port or a number of ports can be statically assigned to that VLAN. A port can belong to only one VLAN at a time.
VLAN configurations can be verified using the show commands.

27. Summary (Cont.)
To add, change, or delete VLANs, the switch must be in VTP server or transparent mode. When VLAN changes are made from a switch that is in VTP server mode, the change is automatically propagated to other switches in the same VTP domain. Changes made in VTP transparent mode affect only the local switch and are not propagated within the VTP domain. VLAN changes cannot be made in VTP client mode.
Misconfiguration of a VLAN is one of the most common errors in switched networks.