How to Configure Inter VLAN Routing

Introduction

VLAN is defined as a virtual local area network or virtual LAN. VLAN is used to divide the broadcast domain of a switch. By default a switch has multiple collision domains and a single broadcast domain.

There are two types of VLANs, they are:

• Static VLAN
• Dynamic VLAN

VTP (VLAN Trucking Protocol)

VTP is defined as VLAN trucking protocol. It is a Cisco proprietary protocol. It is used to manage the inter VLAN communication into a network. Using VTP we can create, delete and modify the network. VTP carries VLAN information to all the switches in a VTP domain. It works with ISL, 802.1q, andIEEE 802.10.

Inter-VLAN Routering

By default one VLAN cannot communicate with another VLAN. To create inter-VLAN communication we need a L3 device like a router or L3 switch. To create inter VLAN routing, we need a make a port trunk port. All VLAN communicate is done with this trunk port.

On the router we create a sub-interface on the router witch is connected with the trunk port of the switch.  All sun interfaces are configured with some encapsulation technique like  ISL or IEEE 802.1q.

Example

In this network we have one switch (L2 switch). In this switch we are creating two the VLANs, VLAN 2 and VLAN 3. VLAN 2 has two computers and has the 192.168.1.0 network. VLAN 3 has three computers and network 192.168.2.0.

Configuration of Switch

Switch>enable Switch#configure terminal Enter configuration commands, one per line.  End with CNTL/Z. Switch(config)#hostname IT IT(config)#enable secret admin IT(config)#enable secret ?   0      Specifies an UNENCRYPTED password will follow   5      Specifies an ENCRYPTED secret will follow   LINE   The UNENCRYPTED (cleartext) 'enable' secret   level  Set exec level password IT(config)#vlan 2 IT(config-vlan)#name it IT(config-vlan)#exit IT(config)#vlan 3 IT(config-vlan)#name hr IT(config-vlan)#exit IT(config)#interface fastEthernet 0/2 IT(config-if)#switchport mode access IT(config-if)#switchport access vlan 2 IT(config-if)#exit IT(config)#interface fastEthernet 0/3 IT(config-if)#switchport mode access IT(config-if)#switchport access vlan 2 IT(config-if)#exit IT(config)#interface fastEthernet 0/11 IT(config-if)#switchport mode access IT(config-if)#switchport access vlan 3 IT(config-if)#exit IT(config)#interface fastEthernet 0/12 IT(config-if)#switchport mode access IT(config-if)#switchport access vlan 3 IT(config-if)#exit IT(config)#interface fastEthernet 0/13 IT(config-if)#switchport mode access IT(config-if)#switchport access vlan 3 IT(config-if)#exit IT(config)#interface vlan 2 IT(config-if)#ip address 192.168.1.1 255.255.255.0 IT(config-if)#no shutdown IT(config-if)#exit IT(config)#interface vlan 3 %LINK-5-CHANGED: Interface Vlan3, changed state to up %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan3, changed state to up IT(config-if)#ip address 192.168.2.1 255.255.255.0 IT(config-if)#no shutdown IT(config-if)#exit IT(config)#interface fa IT(config)#interface fastEthernet 0/1 IT(config-if)#shutdown %LINK-5-CHANGED: Interface FastEthernet0/1, changed state to administratively down %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/1, changed state to down %LINEPROTO-5-UPDOWN: Line protocol on Interface Vlan1, changed state to down IT(config-if)#interface fastEthernet 0/1 IT(config-if)#switchport mode access IT(config-if)#switchport mode trunk

 

Configuration of Router

Router>enable Router#configure terminal Enter configuration commands, one per line.  End with CNTL/Z. Router(config)#interface fastEthernet 0/0 Router(config-if)#no shutdown %LINK-5-CHANGED: Interface FastEthernet0/0, changed state to up %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/0, changed state to up Router(config-if)#interface fastEthernet 0/0.1 %LINK-5-CHANGED: Interface FastEthernet0/0.1, changed state to up %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/0.1, changed state to up Router(config-subif)#encapsulation dot1Q 1 Router(config-subif)#ip address 192.168.1.1 255.255.255.0 Router(config-subif)#no shutdown Router(config-subif)#exit Router(config)#interface fastEthernet 0/0.2 %LINK-5-CHANGED: Interface FastEthernet0/0.2, changed state to up %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/0.2, changed state to up Router(config-subif)#encapsulation dot1Q 2 Router(config-subif)#ip address 192.168.2.1 255.255.255.0 Router(config-subif)#no shutdown

 

It shows all VLAN configured on switch

It shows all configuration of router interface

It show all interfaces of switch

It show all interfaces of router