VLAN

Document revision:	1.2 (Mon Sep 19 13:46:34 GMT 2005)
Applies to:	V2.9

General Information

Summary

VLAN is an implementation of the 802.1Q VLAN protocol for MikroTik RouterOS. It allows you to have multiple Virtual LANs on a single ethernet or wireless interface, giving the ability to segregate LANs efficiently. It supports up to 4095 vlan interfaces, each with a unique VLAN ID, per ethernet device. Many routers, including Cisco and Linux based, and many Layer 2 switches also support it.

A VLAN is a logical grouping that allows end users to communicate as if they were physically connected to a single isolated LAN, independent of the physical configuration of the network. VLAN support adds a new dimension of security and cost savings permitting the sharing of a physical network while logically maintaining separation among unrelated users.

Specifications

Packages required: system
License required: Level1 (limited to 1 vlan) , Level3
Submenu level: /interface vlan
Standards and Technologies: VLAN (IEEE 802.1Q)
Hardware usage: Not significant

Related Documents

Description

VLANs are simply a way of grouping a set of switch ports together so that they form a logical network, separate from any other such group. Within a single switch this is straightforward local configuration. When the VLAN extends over more than one switch, the inter-switch links have to become trunks, on which packets are tagged to indicate which VLAN they belong to.

You can use MikroTik RouterOS (as well as Cisco IOS and Linux) to mark these packets as well as to accept and route marked ones.

As VLAN works on OSI Layer 2, it can be used just as any other network interface without any restrictions. And VLAN successfully passes through Ethernet bridges (for MikroTik RouterOS bridges you should set forward-protocols to ip, arp and other; for other bridges there should be analogical settings).

You can also transport VLANs over wireless links and put multiple VLAN interfaces on a single wireless interface. Note that as VLAN is not a full tunnel protocol (i.e., it does not have additional fields to transport MAC addresses of sender and recipient), the same limitation applies to bridging over VLAN as to bridging plain wireless interfaces. In other words, while wireless clients may participate in VLANs put on wireless interfaces, it is not possible to have VLAN put on a wireless interface in station mode bridged with any other interface.

Currently supported Ethernet interfaces

This is a list of network interfaces on which VLAN was tested and worked. Note that there might be many other interfaces that support VLAN, but they just were not checked.

This is a list of network interfaces on which VLAN was tested and worked, but WITHOUT LARGE PACKET (>1496 bytes) SUPPORT:

Additional Resources

VLAN Setup

Submenu level: /interface vlan

Property Description

arp (disabled | enabled | proxy-arp | reply-only; default: enabled) - Address Resolution Protocol setting

interface (name) - physical interface to the network where are VLANs

mtu (integer; default: 1500) - Maximum Transmission Unit

name (name) - interface name for reference

vlan-id (integer; default: 1) - Virtual LAN identifier or tag that is used to distinguish VLANs. Must be equal for all computers in one VLAN.

Notes

MTU should be set to 1500 bytes as on Ethernet interfaces. But this may not work with some Ethernet cards that do not support receiving/transmitting of full size Ethernet packets with VLAN header added (1500 bytes data + 4 bytes VLAN header + 14 bytes Ethernet header). In this situation MTU 1496 can be used, but note that this will cause packet fragmentation if larger packets have to be sent over interface. At the same time remember that MTU 1496 may cause problems if path MTU discovery is not working properly between source and destination.

Example

To add and enable a VLAN interface named test with vlan-id=1 on interface ether1:

[admin@MikroTik] interface vlan> add name=test vlan-id=1 interface=ether1
[admin@MikroTik] interface vlan> print
Flags: X - disabled, R - running
  #    NAME                 MTU  ARP       VLAN-ID INTERFACE
  0 X  test                 1500 enabled   1       ether1
[admin@MikroTik] interface vlan> enable 0
[admin@MikroTik] interface vlan> print
Flags: X - disabled, R - running
  #    NAME                 MTU  ARP       VLAN-ID INTERFACE
  0  R test                 1500 enabled   1       ether1
[admin@MikroTik] interface vlan>

Application Example

VLAN example on MikroTik Routers

Let us assume that we have two or more MikroTik RouterOS routers connected with a hub. Interfaces to the physical network, where VLAN is to be created is ether1 for all of them (it is needed only for example simplification, it is NOT a must).

To connect computers through VLAN they must be connected physically and unique IP addresses should be assigned them so that they could ping each other. Then on each of them the VLAN interface should be created:

[admin@MikroTik] interface vlan> add name=test vlan-id=32 interface=ether1
[admin@MikroTik] interface vlan> print
Flags: X - disabled, R - running
  #    NAME                 MTU  ARP       VLAN-ID INTERFACE
  0  R test                 1500 enabled   32      ether1
[admin@MikroTik] interface vlan>

If the interfaces were successfully created, both of them will be running. If computers are connected incorrectly (through network device that does not retransmit or forward VLAN packets), either both or one of the interfaces will not be running.

When the interface is running, IP addresses can be assigned to the VLAN interfaces.

On the Router 1:

[admin@MikroTik] ip address> add address=10.10.10.1/24 interface=test
[admin@MikroTik] ip address> print
Flags: X - disabled, I - invalid, D - dynamic
  #   ADDRESS            NETWORK         BROADCAST       INTERFACE
  0   10.0.0.204/24      10.0.0.0        10.0.0.255      ether1
  1   10.20.0.1/24       10.20.0.0       10.20.0.255     pc1
  2   10.10.10.1/24      10.10.10.0      10.10.10.255    test
[admin@MikroTik] ip address>

On the Router 2:

[admin@MikroTik] ip address> add address=10.10.10.2/24 interface=test
[admin@MikroTik] ip address> print
Flags: X - disabled, I - invalid, D - dynamic
  #   ADDRESS            NETWORK         BROADCAST       INTERFACE
  0   10.0.0.201/24      10.0.0.0        10.0.0.255      ether1
  1   10.10.10.2/24      10.10.10.0      10.10.10.255    test
[admin@MikroTik] ip address>

If it set up correctly, then it is possible to ping Router 2 from Router 1 and vice versa:

[admin@MikroTik] ip address> /ping 10.10.10.1
10.10.10.1 64 byte pong: ttl=255 time=3 ms
10.10.10.1 64 byte pong: ttl=255 time=4 ms
10.10.10.1 64 byte pong: ttl=255 time=10 ms
10.10.10.1 64 byte pong: ttl=255 time=5 ms
4 packets transmitted, 4 packets received, 0% packet loss
round-trip min/avg/max = 3/10.5/10 ms
[admin@MikroTik] ip address> /ping 10.10.10.2
10.10.10.2 64 byte pong: ttl=255 time=10 ms
10.10.10.2 64 byte pong: ttl=255 time=11 ms
10.10.10.2 64 byte pong: ttl=255 time=10 ms
10.10.10.2 64 byte pong: ttl=255 time=13 ms
4 packets transmitted, 4 packets received, 0% packet loss
round-trip min/avg/max = 10/11/13 ms
[admin@MikroTik] ip address>