Chapter 9 Virtual LANs (VLANs)

Setup 1

Setup 2

Setup 3 VLAN Advantages 1- Broadcast Control 2- Security 3- Flexibility and Scalability

Managing VLANs 1- Create VLAN 2- Assign ports to VLANS: Static or Dynamic using VLAN Management Policy Server (VMPS) In 1900 Series Step11900A(config)#vlan 2 name Sales Step21900A(config)#int f0/1 1900A(config-if)#vlan-membership static A(config-if)#^Z Step31900A#sh vlan

Managing VLANs In 2950 Series Step12950B#vlan database 2950B(vlan)#vlan 2 name Sales 2950B(vlan)#apply OR 2950B(config)#vlan B(config-vlan)#name Sales Step22950B(config)#int f0/1 2950B(config-if)#switchport mode ? access Set trunking mode to ACCESS unconditionally dynamic Set trunking mode to dynamically negotiate access or trunk mode trunk Set trunking mode to TRUNK unconditionally 2950B(config-if)#switchport mode access 2950B(config-if)#switchport access vlan B(config-if)#^Z Step32950B#sh vlan 2950B#sh vlan brief

Connecting VLANs VLAN 3VLAN 2VLAN 4VLAN 3VLAN 2VLAN 4 1- Access Link A.L

VLAN 3VLAN 2VLAN 4VLAN 3VLAN 2VLAN 4 2- Trunk Link T.L

VLAN Identification in Trunks ISL (Inter-Switch Link) IEEE 802.1q * Cisco proprietary * Open Standard encapsulation method * 1900 Series * 2950 Series FCSFrameVLAN ID Trunk Link Tagging Frames

Configuring Trunking In 1900 Series 1900A(config)#int f0/ A(config-if)#trunk on off auto desirable non-negotiate In 2950 Series 2950B(config)#int f0/ B(config-if)#switchport mode trunk 2950B(config-if)#switchport mode dynamic auto 2950B(config-if)#switchport mode dynamic desirable 2950B(config-if)#switchport nonegotiate

Configuring Trunking 1- Auto: Changes to Trunk if available (default) 2- Desirable: Changes to Trunk if neighbor port is Trunk, Desirable or Auto. 3- Nonegotiate: The neighbor must be either Trunk or Access. 4- Trunk: Makes link Trunk even if neighbor port is Access.

In 3550 Series 3550C(config)#int f0/ C(config-if)#switchport trunk encapsulation ? dot1q Interface uses only 802.1q trunking encapsulation when trunking isl Interface uses only ISL trunking encapsulation when trunking negotiate Device will negotiate trunking encapsulation with peer on interface 3550C(config-if)#switchport trunk encapsulation dot1q

Defining the Allowed VLANs on a Trunk 2950B(config)#int f0/1 2950B(config-if)#switchport trunk ? allowed Set allowed VLAN characteristics when interface is in trunking mode native Set trunking native characteristics when interface is in trunking mode pruning Set pruning VLAN characteristics when interface is in trunking mode 2950B(config-if)#switchport trunk allowed vlan ? WORD VLAN IDs of the allowed VLANs when this port is in trunking mode add add VLANs to the current list all all VLANs except all VLANs except the following none no VLANs remove remove VLANs from the current list 2950B(config-if)#switchport trunk allowed vlan remove ? WORD VLAN IDs of disallowed VLANS when this port is in trunking mode 2950B(config-if)#switchport trunk allowed vlan remove B(config-if)#switchport trunk allowed vlan remove 4-8

Modifying the Trunk Native VLAN 2950B(config-if)#switchport trunk native vlan ? VLAN ID of the native VLAN when this port is in trunking mode 2950B(config-if)#switchport trunk native vlan 40 19:23:29: %CDP-4-NATIVE_VLAN_MISMATCH: Native VLAN mismatch discovered on FastEthernet0/1 (40), with Core FastEthernet0/7 (1). 19:24:29: %CDP-4-NATIVE_VLAN_MISMATCH: Native VLAN mismatch discovered on FastEthernet0/1 (40), with Core FastEthernet0/7 (1). 2950B(config-if)#no switchport trunk native vlan

Routing between VLANs

Router#config t Router(config)#int f0/0.1 Router(config-subif)#encapsulation ? dot1Q IEEE 802.1Q Virtual LAN Router(config-subif)#encapsulation dot1Q ? IEEE 802.1Q VLAN ID Router(config-subif)#encapsulation dot1Q 2 Router(config-subif)# int f0/0.2 Router(config-subif)#encapsulation dot1Q 3

2950B#config t 2950B(config)#int f0/1 2950B(config-if)#switchport mode trunk 2950B(config-if)#int f0/2 2950B(config-if)#switchport access vlan B(config-if)#int f0/3 2950B(config-if)#switchport access vlan B(config-if)#int f0/4 2950B(config-if)#switchport access vlan B(config-if)#int f0/5 2950B(config-if)#switchport access vlan B(config-if)#int f0/6 2950B(config-if)#switchport access vlan 2 Router(config)#int f0/0 Router(config-if)#no ip address Router(config-if)#no shutdown Router(config-if)#int f0/0.1 Router(config-subif)#encapsulation dot1q 1 Router(config-subif)#ip address Router(config-subif)#int f0/0.2 Router(config-subif)#encapsulation dot1q 2 Router(config-subif)#ip address Router(config-subif)#int f0/0.3 Router(config-subif)#encapsulation dot1q 3 Router(config-subif)#ip address

VLAN Trunking Protocol (VTP) Creates VLANs Modifies VLANs Deletes VLANs Sends and forwards advertisements Synchronizes Saved in NVRAM Can not Create, Modify or Delete VLANs Sends and forwards advertisements Synchronizes Not saved in NVRAM Creates local VLANs only Modifies local VLANs only Deletes local VLANs only Sends and forwards advertisements Does not Synchronizes Saved in NVRAM

2950B#(config)#vtp mode server Device mode already VTP SERVER. 2950B(config)#vtp domain Cisco Changing VTP domain name from null to Cisco 2950B(config)#vtp password cisco Setting device VLAN database password to cisco 2950B(config)#do show vtp password VTP Password: cisco 2950B(config)#do show vtp status VTP Version : 2 Configuration Revision : 0 Maximum VLANs supported locally : 255 Number of existing VLANs : 8 VTP Operating Mode : Server VTP Domain Name : Cisco VTP Pruning Mode : Disabled VTP V2 Mode : Disabled VTP Traps Generation : Disabled MD5 digest : 0x15 0x54 0x88 0xF2 0x50 0xD9 0x03 0x07 Configuration last modified by at :47:32 Local updater ID is on interface Vl1 (lowest numbered VLAN interface found)

VTP Pruning

2950B#sh int trunk Port Mode Encapsulation Status Native vlan Fa0/1 auto 802.1q trunking 1 Fa0/2 auto 802.1q trunking 1 Port Vlans allowed on trunk Fa0/ Fa0/ Port Vlans allowed and active in management domain Fa0/1 1 Fa0/2 1 Port Vlans in spanning tree forwarding state and not pruned Fa0/1 1 Fa0/2 none 2950B(config-if)#switchport trunk pruning ? vlan Set VLANs enabled for pruning when interface is in trunking mode 2950B(config-if)#switchport trunk pruning vlan 3-4

Telephony: Configuring Voice VLANs IP phone sends voice traffic with layer 3 IP precedence and layer 2 class of service (CoS) values, which are both set to 5 for voice traffic; all other traffic defaults to 0. The switch supports quality of service (QoS) based on IEEE 802.1p CoS. (802.1p provides a mechanism for implementing QoS at the MAC level.) By using CDP we can deal with: Voice VLAN tagged with a layer 2 CoS priority value Access VLAN tagged with a layer 2 CoS priority value Access VLAN, untagged (no layer 2 CoS priority value)

Consider the following: 1.Use Access Ports. 2.Set Voice VLAN Correctly 3.Enable QoS before enabling Voice VLAN by using the command 2950B(config)#mls qos 4.You must set the port trust state to trust by using the command 2950B(config-if)#mls qos trust cos 5.Enable CDP 6.Portfast is auto enbled when you enable Voice VLAN but not auto disabled when you disable Voice VLAN 7.You can back to default settings by using the command 2950B(config-if)#no switchport voice vlan

2950B#configure t 2950B(config)#mls qos to enable QoS 2950B(config)#interface f0/1 2950B(config-if)#switchport priority extend ? cos Override 802.1p priority of devices on appliance trust Trust 802.1p priorities of devices on appliance 2950B(config-if)#switchport priority extend trust to define untagged CoS with value = B(config-if)#mls qos trust cos setting trust 2950B(config-if)#switchport voice vlan dot1p 2950B(config-if)#switchport mode access 2950B(config-if)#switchport access vlan B(config-if)#switchport voice vlan 10