One of the most difficult configuration challenges for MikroTik equipment seems to be switching and VLANs in the CRS series. Admittedly, the revamp of VLAN configuration for MikroTik CRS switches in early 2018 made things a lot easier. But, sometimes there is still confusion on how to configure VLANs and IP addresses in VLANs with MikroTik RouterOS operating on a switch.
This will only cover VLAN configuration for CRS 3xx series switches in RouterOS as SwitchOS is not nearly as common in operational deployments.
CRS 1xx/2xx series use an older style of configuration and seem to be on the way out so I’m not 100% sure whether or not i’ll write a similar guide on that series.
If you’ve been in networking for a while, you probably started with learning the Cisco CLI. Therefore, it is helpful to compare the commands if you want to implement a network with a MikroTik and Cisco switches.
This is the fourth post in a series that creates a Rosetta stone between IOS and RouterOS. Here are some of the others:
Click here for the first article in this series – “Cisco to MikroTik BGP command translation” Click here for the second article in this series – “Cisco to MikroTik OSPF command translation” Click here for the third article in the series – “Cisco to MikroTik MPLS command translation”
While many commands have almost the exact same information, others are as close as possible. Since there isn’t always an exact match, sometimes you may have to run two or three commands to get the information needed.
Hardware for testing
In the last article, we began using EVE-NG instead of GNS3 to emulate both Cisco IOS and RouterOS so we could compare the different commands and ensure the translation was as close as possible. However in switching, we still have to use real hardware at least in the realm of MikroTik – Cisco has IOSvL2 images that can be used in EVE-NG for switching.
Notes on hardware bridging in the CRS series
Bridging is a very confusing topic within the realm of MikroTik equipment. It is often associated with CPU forwarding and is generally seen as something to be avoided if at all possible.
There are a few reasons for this…
1. Within routers, bridging generally does rely on the CPU for forwarding and the throughput is limited to the size of the CPU.
2. In the previous generation of CRS configuration, bridging was not the best way to configure the switch – using the port master/slave option would trigger hardware forwarding.
After MikroTik revamped the switch config for VLANs in 2018 to utilize the bridge, it more closely resembles the style of configuration for Metro Ethernet Layer 2 as well as vendors like Juniper that use the ‘bridge-domain’ style of config.
Using the bridge for hardware offload of L2 traffic
Note the Hw. Offload verification under this bridge port in the CRS317
It is important to realize that bridging in the CRS, when used for VLAN configuration is actually using the switch ASIC to forward traffic and not the CPU.
In this instance, the bridge is merely used as a familiar configuration tool to tie ports and VLANs together but does in fact allow for the forwarding of traffic in hardware at wirespeed.
Cisco to MikroTik – command translation
switchport access vlan 100
switchport mode access
/interface bridge port
add bridge=bridge1 interface=sfp-sfpplus1 pvid=100
This command will set the bridge loop prevention protocol to Multiple Spanning Tree. As a general observation, MSTP tends to be the most compatible across vendors as some vendors like Cisco use a proprietary version of Rapid STP.
This is referred to as “portfast” in the Cisco world and allows a port facing a device that isn’t a bridge or a switch to transition immediately to forwarding but if it detects a BPDU, it will revert to normal STP operation. (this is the difference between edge=yes and edge=yes-discover)
[admin@MikroTik]>/interfacebridge port set edge=yes-discover
This command will create a bonding interface which is similar to a Port Channel in Cisco’s switches. Two or more physical interfaces can be selected to bond together and then the 802.3ad mode is selected which is LACP. You can also select the hashing policy and ideally it should match what the device on the other end is set for to get the best distribution of traffic and avoid interoperability issues.