InterVLAN Routing with Internet Access on Ubuntu

topology

Scenario:

  • Router: Ubuntu Server with 1 network card.
  • Clients:  WindowsXP in VLAN10,Windows7 in VLAN20.
  • Internet: Internet Router on VLAN30
  • Switch: Cisco 2960
Cisco 2960 Switch Configuration:
interface FastEthernet0/12
description CONNECTED TO UBUNTU ROUTER
switchport mode trunk
!
!
interface FastEthernet0/1
description WINXP
switchport access vlan 10
switchport mode access
!
!
interface FastEthernet0/2
description Win7
switchport access vlan 20
switchport mode access
!
!
interface FastEthernet0/24
description Internet Router
switchport access vlan 30
switchport mode access

Ubuntu Router Configuration:

To install the vlan support on ubuntu, use this command:

sudo apt-get install vlan

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Now we shall configure the vlans on Ubuntu router by editing the /etc/network/interfaces:

sudo nano /etc/network/interfaces

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To enable ip forwarding, edit /etc/sysctl.conf file:

sudo nano /etc/sysctl.conf

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Change net.ipv4.ip_forward from 0 to 1:

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Load “8021q” kernel module:

sudo modprobe 8021q

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Restart the Networking service:

sudo /etc/init.d/networking restart

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Verify the vlan configuration:

sudo cat /proc/net/vlan/config

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In order to provide internet access to Vlan 10 and 20 client(s), we need to do NAT on Vlan 30 interface, on which we have configured the Gateway:

sudo iptables -t nat -A POSTROUTING -o vlan30 -j MASQUERADE

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Verify the routing information on Ubuntu:

sudo route -n

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Test from WinXP:

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Test from Win7:

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Hope this will help you!

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