Virtual Interfaces and VLANs in Fedora20

Setting up VLAN interfaces in Fedora20

VLAN is an acronym for Virtual Local Area Network. Several VLANs can co-exist on a single physical switch, which are configured via Linux software and not through hardware interface (you still need to configure actual hardware switch too).

Hardware Device Requirements
• To be able to use VLANs you will need a switch that support the IEEE 802.1q standard on an Ethernet network.
• You will also need a NIC (Network Interface Card) that works with Linux and support 802.1q standard.

Setting Up 802.1q VLAN Tagging

This is based on Fedora documentation, specifically F17-System Administrators Guide http://docs.fedoraproject.org/en-US/Fedora/17/html/System_Administrators_Guide/s2-networkscripts-interfaces_802.1q-vlan-tagging.html .
• First, ensure that the 8021q kernel module is loaded with the following command:

# lsmod | grep 8021q

# modprobe 8021q

is the command to load it if no output results from the grep command above.
• Configure the physical interface by editing the /etc/sysconfig/network-scripts/ifcfg-enp0s25 file, where enp0s25 is the name of the physical interface. The configuration file for the physical interface should look as follows:

DEVICE=enp0s25

TYPE=Ethernet

BOOTPROTO=none

ONBOOT=yes

• Copy the configuration file of the physical interface to a VLAN interface configuration file by appending a .(period) character and the VLAN ID number to the VLAN interface filename:

∘ # cp /etc/sysconfig/network-scripts/ifcfg-enp0s25{,.5}

creates a new file for our VLAN interface, the ID number of which is 5 within the system-wide network directory mentioned above.
• Edit the VLAN interface configuration file so that it matches the following example:

DEVICE=enp0s25.5

BOOTPROTO=static

ONBOOT=yes
IPADDR=192.168.1.1

NETMASK=255.255.255.0

USERCTL=no

NETWORK=192.168.1.0

VLAN=yes

• Restart the networking service

∘ # systemctl restart NetworkManager.service

If the network router is acting as the DHCP server (sharing a single IP address from the ISP), restarting the networking service as mentioned above might display some messages from the router with a different IP address if it's not configured to provide a static address to the interface.

Method 2: Using the vconfig Command

The vconfig program allows you to create and remove vlan-devices on a vlan-enabled kernel. VLAN-devices are virtual ethernet devices which represent the virtual LANs on the physical LAN. To add a virtual interface with ID number 5, for example, execute:

# vconfig add enp0s25 5

# ifconfig enp0s25.5

will show the newly-created VLAN interface along with its configured parameters.
• The ifconfig command can also be used to directly assign an IP address to the VLAN interface:

∘ # ifconfig enp0s25.5 192.168.1.100 255.255.255.0 broadcast 192.168.1.255 up

• To get more detailed information about the interface execute:

∘ # cat /proc/net/vlan/enp0s25

Method 3: ip command for VLANs

∘ # ip link add link enp0s25 name enp0s25.5 type vlan id 5

∘ # ip link

∘ # ip -d link show enp0s25.5

• Once again, as with ifconfig above, assign an IP address to the VLAN interface:

∘ # ip addr add 192.168.1.200/24 brd 192.168.1.255 dev enp0s25.5

∘ # ip link set dev enp0s25.5 up

• The enp0s25 interface will handle the traffic for both, the VLAN's address as well as its own; however, the VLAN's traffic will be tagged with a VLAN ID tag 5. Only VLAN-aware devices can accept the traffic using VLAN tagging.
• To remove the VLAN tagging from the IP packets, use the following commands:

∘ # ip link set dev enp0s25.5 down

∘ # ip link delete enp0s25.5