Configure VLAN in Cisco Catalyst Switch

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If you have basic understanding of VLANs in Switching World then you can easily configure VLANs in Cisco Catalyst switches. In this post, I will show steps to Configure VLAN in Cisco Catalyst Switch.

Configure VLAN in Cisco Catalyst Switch

The diagram below shows our scenario. There are two switches, Switch1 and Switch2. We will create VLAN 2 and VLAN 3 in both switches, assign ports into VLANs and configure TRUNK between the switches.

Configure VLAN in Cisco Catalyst Switch

Let’s start with Switch1.

Switch1(config)#vlan 2
Switch1(config-vlan)#name Support
Switch1(config)#vlan 3
Switch1(config-vlan)#name Marketing

Above commands creates two VLANs named Support and Marketing with VLAN ID 2 and 3 respectively. Now, let’s assign ports to VLANs. Let’s assign port fa0/1 and fa0/5 to VLAN3 first. Note: – When you create a new VLAN, a spanning-tree instance and mac address table are also created by default.

Switch1(config)#int fa0/1
Switch1(config-if)#switchport mode access 
Switch1(config-if)#switchport access vlan 3
Switch1(config)#int fa0/5
Switch1(config-if)#switchport mode access 
Switch1(config-if)#switchport access vlan 3

To assign multiple interfaces at a time we use interface range command as shown below for VLAN 2.

Switch1(config)#interface range fastEthernet 0/3 - 4
Switch1(config-if-range)#switchport mode access 
Switch1(config-if-range)#switchport access vlan 2

To verify if VLANs have been created, use show vlan command as shown below.

Switch1#show vlan 

VLAN Name                             Status    Ports
---- -------------------------------- --------- -------------------------------
1    default                          active    Fa0/2, Fa0/6, Fa0/7, Fa0/8
                                                Fa0/9, Fa0/10, Fa0/11, Fa0/12
                                                Fa0/13, Fa0/14, Fa0/15, Fa0/16
                                                Fa0/17, Fa0/18, Fa0/19, Fa0/20
                                                Fa0/21, Fa0/22, Fa0/23, Fa0/24
                                                Gig0/1, Gig0/2
2    Support                          active    Fa0/3, Fa0/4
3    Marketing                        active    Fa0/1, Fa0/5
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   

As you can see above, ports fa0/3 and fa0/4 are in VLAN2 and ports fa0/1 and fa0/5 are on VLAN3. You can repeat exact same steps on Switch2 as well. Now, let’s configure TRUNK ports starting with Switch1.

Switch1(config)#int fa0/6
Switch1(config-if)#switchport trunk encapsulation dot1q 
Switch1(config-if)#switchport mode trunk 

%LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/6, changed state to down

%LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/6, changed state to up

The command above configured port fa0/6 as TRUNK port and the encapsulation protocol is dot1q. Repeat the same step on Switch2. To verify the trunk port you can use command show interfaces trunk.

Switch1#show interfaces trunk 
Port        Mode         Encapsulation  Status        Native vlan
Fa0/6       on           802.1q         trunking      1

Port        Vlans allowed on trunk
Fa0/6       1-1005

Port        Vlans allowed and active in management domain
Fa0/6       1,2,3

Port        Vlans in spanning tree forwarding state and not pruned
Fa0/6       1,2,3

As you can see above, interface fa0/6 status is trunking, native vlan is 1 and encapsulation is 802.1Q. Vlans allowed on trunk is 1 to 1005, this means 1 to 1005 VLAN IDs can pass through this trunk. Vlans allowed and active in management domain means, VLAN 1,2 and 3 have been created in this switch and are active. Vlans in spanning tree forwarding state and not pruned means, frames can be sent and received by all three (1,2 and 3) VLANs. You can also view more detail of the trunk interface using, show interface fa0/6 switchport command as shown below,

Switch1#show int fa0/6 switchport 
Name: Fa0/6
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: 1 (default)
Voice VLAN: none
Administrative private-vlan host-association: none
Administrative private-vlan mapping: none
Administrative private-vlan trunk native VLAN: none
Administrative private-vlan trunk encapsulation: dot1q
Administrative private-vlan trunk normal VLANs: none
Administrative private-vlan trunk private VLANs: none
Operational private-vlan: none
Trunking VLANs Enabled: All
Pruning VLANs Enabled: 2-1001
Capture Mode Disabled
Capture VLANs Allowed: ALL
Protected: false
Unknown unicast blocked: disabled
Unknown multicast blocked: disabled
Appliance trust: none

The above command shows lot of details of interface fa0/6. Switchport:enabled means the port is working as layer 2 port, not layer 3. Administrative mode:trunk means, we manually specified the port as trunk. Operational mode: trunk means the port is trunking. Administrative trunking encapsulation: dot1q means the encapsulation is set to dot1q. Operational trunking encapsulatioin: dot1q means the trunking protocol running is dot1q. Negotiation of trunking: on means the DTP (Dynamic Trunking Protocol) is on. Trunking Native Mode VLAN: 1 (default) means the native VLAN is 1 and it’s the default behavior.

Now, assign IP to the PCs of both VLANs. You can ping another PC within same VLAN but not to another VLAN. You need a router to make communication occur between two VLANs. Most popular form of VLAN routing is router on a stick. So, this is how you can configure VLAN in Cisco Catalyst Swtich.

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Bipin is a freelance Network and System Engineer with expertise on Cisco, Juniper, Microsoft, VMware, and other technologies. You can hire him on UpWork. Bipin enjoys writing articles and tutorials related to Network technologies. Some of his certifications are, MCSE:Messaging, JNCIP-SEC, JNCIS-ENT, and others.

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