Hi, I would like to have MTU 1500 for PPPoE over VLAN. So to accommodate the pppoe header I set the MTU of the VLAN interface to 1508. This results in the PPPoE status showing MRU 1500 but MTU increased only to 1496. I tried setting higher values, also on the physical interface and the max-mtu o…

[image] tdw: interface MTU setting is irrelevant for PPPoE traffic YUP [interface MTU setting is irrelevant for PPPoE traffic] While you are right that the value is irrelevant for the PPPoE traffic itself, it is not irrelevant for auto MRU/MTU negotiation (the client looks at the parent int…

What you want is to increase the mtu on ether interface tied to your pppoe [Screenshot from 2026-05-31 19-48-27] [Screenshot from 2026-05-31 19-47-47]

Just setting max-mtu and max-mru (all interfaces MTU reset to default) and VLAN on physical interface: [image] The log does not show anything regarding MTU... 2026-05-31T21:18:23.632536+02:00 router1 pppoe,ppp,info pppoe1: initializing... 2026-05-31T21:18:23.632536+02:00 router1 pppoe,ppp,info p…

Here is my configuration, Vodafone PPPoE over vlan 911 on sfp-sfpplus1: [image] sfp-sfpplus1 & vlan911 both manually set to MTU 1508, PPPoE client then automatically connects at 1500. [image] Sounds like if this doesn't work for you there's something not quite right at the ISP end. The standar…

ISP may not support full 1500 MTU on PPPoE. Either on purpose or by misconfiguration.

[image] rextended: The "MTU" must not be changed anywhere Explain this then MTU for PPPoE over VLAN - #5 by Znevna You are not the first to make this claim anyway. I did complain to support about the behaviour that MikroTik had until RouterOS 7.2 regarding the PPPoE client always trying to…

If the hardware is made by MikroTik, and the interface has a value for the L2MTU field, then there is no need to increase or modify the MTU value of any underlaying interface. They can all keep the default value of 1500. What you did not do in your screencap, was to do recommended thing and set Max …

So, to summarize: there is no RFC or standard that recommends blindly hardcoding Max MTU/MRU over the documented auto-negotiation process. Furthermore, your method of doing so while intentionally ignoring the parent interface MTU actually breaks RouterOS's Change TCP MSS behaviour, forcing users to…

I've had a headache dozens of times, for wrong labels (L3MTU / L2MTU)... but my entire customers network has an L3-MTU of 1500, with the exception of some non-MikroTik point-to-points which also mean L2MTU by MTU and need to be increased to allow PPPoE+VLAN to pass... VLAN can not consider (L3)MT…