Mikrotik VLAN Trunking
VLAN (Virtual Local Area Network) is not something new and unique to Mikrotik networking devices. It is an amazing technology we have to segregate the different LANs on Layer 2 switching. Different vendors implement the VLAN and VLAN trunking technology differently but all follows the same 802.1q standard for tagging and untagging VLANs on their devices.
In this article, I would like to demostrate the VLAN capability on Mikrotik and how we can configure it easily in RouterOS. Note that most of the Mikrotik networking devices come with dedicated switch chip on RouterBoard to perform hardware offloading for more efficient switching at Layer 2 rather than passing the loads to main CPU. Since the Mikrotik device comes with RouterOS can configured as router with sub-interface for VLAN tagging which you would see it commonly in router-on-a-stick scenario, and switch with proper VLAN tagging and untagging to utilise the dedicated switch chip on RouterBoard.
Prerequisites
GNS3 Emulator
Mikrotik CHR appliance setup on GNS3
Mikrotik RouterOS version 7.7
Basic level of comfortableness with Mikrotik RouterOS CLI and GNS3 setup
Network Topology
Two swtiches - mtr2 and mtr3; each has two VLANs namely ops1 and ops2
One router - mtr1 which is bridging between two switches with routing capability for internet breakout to NAT1 cloud and inter-VLAN routing
Configuration
mtr1 router config
This mtr1 is used as a router therefore it uses the software VLAN sub-interfaces on the physical port of the device. Here is the full configuration of mtr1 router on the top of its topology.
mtr2 switch config
On this mtr2 switch, the way to configure the VLANs is very similar to how it is configured on mtr1 except it doesn't have any routing related configuration. This sort of VLAN setup can also be used to function as L2 switch in RouterOS in case you want to use it for switching capability on the device. In my opinion, the SwOS used for CRS and CSS series from Mikrotik still have a few years to get the point of its maturity thus I think it is a safe bet to stick to RouterOS for now even though you only want to use as a switch. Note that the CSS series are not compatible with RouterOS but only with SwOS. Here is the full configuraiton of mtr2 switch config.
As you can see in the config, there is no VLAN tagging and untagging but purely use the bridge feature available on Mikrotik to map the VLAN sub-interface and physical ether port(s) to the downstream. It is very simple but powerful to pull it off like that. But it is not the most efficient way to configure the VLAN trunking on Mikrotik
mtr3 switch config
This mtr3 switch will be used to demonstrate the most efficient way to configure VLAN trunking by utilising switch chip and hardware offloading available on Mikrotik devices. You will notice that there is no software VLAN sub-interface fashion on this device but it uses the VLAN tagging and untagging concept on one main bridge as below.
Alternatively, we can configure its VLAN setup in a very similar manner but it is only fancier with relevant frame-types option. Note that the ingress is configured at bridge ports and egress at bridge vlans.
As much compact as it can be for the configuration on this mtr3 device, it is the most efficient way to configure the Mikrotik device with RouterOS for switching.
By now, all of the PCs behind the mtr2 and mtr3 switches should have been assigned with the respective IP addresses from DHCP server running on mtr1 router. They should be able to ping to the gateway router mtr1 and to the internet
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