RouterOS and MTU - a collection of useful scripts

Share your Config Push presets or discuss automation in general
Post Reply
User avatar
Tomas
Posts: 1118
Joined: Sat Jun 25, 2016 12:33 pm

Tue Feb 08, 2022 3:19 pm

We just published an article on finding MTU issues on MikroTiks, and a collection of useful MTU scripts for RouterOS.

- Auditing L2 MTU across your MikroTiks
- Setting L2 MTU (enabling jumbo frames)
- Auditing L3 MTU across your MikroTiks
- Setting L3 MTU
- Check and set MPLS MTU

Link to the blog article:
https://blog.unimus.net/routeros-and-mt ... l-scripts/

This is an accompanying forum topic to this blog article, please feel free to post any feedback here!
manish
Posts: 1
Joined: Sat Aug 06, 2022 4:24 pm

Sat Aug 06, 2022 4:54 pm

Tomas,

Thank you for the article, I want to try to maximise the MTU, I have a working OFPS/MPLS, working on 1600mtu; due to some limitations on a few segments, can I run the script and maximise the MTU? and will it affect the working of MPLS or OSPF?

Thank you,

Manish
User avatar
Tomas
Posts: 1118
Joined: Sat Jun 25, 2016 12:33 pm

Mon Aug 08, 2022 2:36 pm

manish wrote:
Sat Aug 06, 2022 4:54 pm
I want to try to maximise the MTU, I have a working OFPS/MPLS, working on 1600mtu; due to some limitations on a few segments, can I run the script and maximise the MTU? and will it affect the working of MPLS or OSPF?
The L2 MTU you can max across the network without any negative consequences. The MPLS and L3 MTU are however different. You MUST assure all the hops transiting the MPLS frames (or IP packets) can support the requested MTU on lower layers.

Basically, all the lower layers MUST support transiting frames of the desired size first, before you can increase MTU on "upper" layers. So if you have some unmanaged switches, or some switches which you can't increase L2 MTU on, you should NOT increase MPLS nor L3 MTUs, or it will break your network.

I have an older presentation here I would recommend checking out - it delves deeper into MTU: https://youtu.be/Q8AF-Srulmk
Post Reply