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Assigning IP Addresses to VLANs on Cisco Switch

Introduction

Earlier, I wrote an article about VLAN configuration on a Cisco switch. You can read it here: VLAN Configuration on a Cisco Switch

In that article, we learned how to create VLANs and assign ports to them.

In this article, we will go a step further and assign IP addresses to each VLAN. Assigning IP addresses is important because devices in each VLAN can then communicate with other devices in the same VLAN or even in other VLANs (if routing is configured).

We will configure these VLANs on switch S1:

IT - VLAN 10 - 172.16.10.0/24

HR - VLAN 20 - 172.16.20.0/24

SALES - VLAN 30 - 172.16.30.0/24

GUEST - VLAN 40 - 172.16.40.0/24

Step 1. Create VLANs on S1

First, make sure the VLANs exist on the switch. If you followed the previous article, the VLANs should already be there. If not, create them using these commands:

  
    S1> enable
S1# configure terminal

S1(config)# vlan 10
S1(config-vlan)# name IT
S1(config-vlan)# exit

S1(config)# vlan 20
S1(config-vlan)# name HR
S1(config-vlan)# exit

S1(config)# vlan 30
S1(config-vlan)# name SALES
S1(config-vlan)# exit

S1(config)# vlan 40
S1(config-vlan)# name GUEST
S1(config-vlan)# exit

Step 2. Assign Ports to VLANs

We also need to assign switch ports to the correct VLANs. For example:

IT - Fa0/1 to Fa0/5

HR - Fa0/6 to Fa0/10

SALES - Fa0/11 to Fa0/15

GUEST - Fa0/16 to Fa0/20

  
    S1(config)# interface range fa0/1 - 5
S1(config-if-range)# switchport mode access
S1(config-if-range)# switchport access vlan 10
S1(config-if-range)# exit

S1(config)# interface range fa0/6 - 10
S1(config-if-range)# switchport mode access
S1(config-if-range)# switchport access vlan 20
S1(config-if-range)# exit

S1(config)# interface range fa0/11 - 15
S1(config-if-range)# switchport mode access
S1(config-if-range)# switchport access vlan 30
S1(config-if-range)# exit

S1(config)# interface range fa0/16 - 20
S1(config-if-range)# switchport mode access
S1(config-if-range)# switchport access vlan 40
S1(config-if-range)# exit

Step 3. Assign IP Addresses to VLANs

Next, we will give each VLAN an IP address. This IP will act as a default gateway for devices in that VLAN.

  
    S1(config)# interface vlan 10
S1(config-if)# ip address 172.16.10.1 255.255.255.0
S1(config-if)# no shutdown
S1(config-if)# exit

S1(config)# interface vlan 20
S1(config-if)# ip address 172.16.20.1 255.255.255.0
S1(config-if)# no shutdown
S1(config-if)# exit

S1(config)# interface vlan 30
S1(config-if)# ip address 172.16.30.1 255.255.255.0
S1(config-if)# no shutdown
S1(config-if)# exit

S1(config)# interface vlan 40
S1(config-if)# ip address 172.16.40.1 255.255.255.0
S1(config-if)# no shutdown
S1(config-if)# exit
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Step 4. Save the Configuration

To save your work and make sure it stays after the switch restarts:

  
    S1# copy running-config startup-config
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Step 5. Verify VLANs and IPs

  • Check the VLANs and their ports:

  
    S1# show vlan brief
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  • Check the IP addresses of VLAN interfaces

  
    S1# show ip interface brief
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Conclusion

In this article, we gave IP addresses to four VLANs on switch S1: IT, HR, SALES, and GUEST. Each VLAN has its own IP address and ports, so the networks are separate and organized. Devices in each VLAN can use the IP address as a gateway to connect inside the VLAN. This makes the network safer, faster, and easier to manage. For more information about creating VLANs and assigning ports, you can read my previous article: VLAN Configuration on a Cisco Switch

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