I have a friend subscribing to UniFiBiz 5 Static IPs.

If I configure the PPPoE dialer with MTU and MRU as 1492, she gets her correct /29 static IPs.

If I configure the PPPoE dialer with no MTU nor MRU set, she gets a dynamic IP. The MTU eventually ends up as 1480

Anyone know why that is?

This post has been edited by soonwai: Feb 25 2017, 02:50 AM

i think as long as below 1500 should be fine. MTU just a frame size. as far i know TM MTU max 1500.

i already play around MTU for my unifi and max MTU size can be configure 1492.

I know right. So wierd. Why does TM's pppoe server react differently just because the pppoe client is dialing with a different MTU and MRU size?

it might cause by auth server dialer. but why i dont have answer. hehehehe

it seem tplink router default at mtu 1480 since beginning?

Mikrotik default is also 1480. Some Dlinks are at 1492. 1492 is the max you can go for PPP due to the 8 byte overhead of PPP and PPPoE but having some extra space is always safer.

HI the reason for this MTU issue is very simple.
MTU means the largest size of data transmission via a network path
The MTU size id dynamic means that it can be several variable below a ciling size
This variable is auto detected by the ICMP protocol
The entire ICMP protocol family is blocked by TM Unifi.
IF TM unifi can identify which or their devices blocked the ICMP protocol than this issue wont arise anylonger
The ICMP protocol is responsible to auto detect the MTU than make use of the dynimaic setting to make the VPN work right away
About the VPN ...VPN protocl tends to load more header than the common way of cimmunication thus this is waht causing what you are experinceing right now
so:
1. Either TM allow ICMP protocol or
2. All TM Customers entire malaysia need to manualy adjust this MTU

Thanks, your first line is very clear. Which of your following lines did the first refer to?

Just to share...

https://www.sonicwall.com/support/knowledge...70505851231244/

It is generally recommended that the MTU for a WAN interface connected to a PPPoE DSL network be 1492. In fact, with auto MTU discovery, 1492 is discovered to be the maximum allowed MTU. However, having an MTU of 1452 is most optimal.

https://www.techrepublic.com/article/how-to...er-performance/


This post has been edited by rodyeo: Sep 11 2021, 12:12 AM

Have tried MTU 1500 on PPPoE? (ETH need MTU 1508)

MTU 1452 is optimal for PPPoE connection as endorsed by many solution providers like Cisco already!


https://www.techrepublic.com/article/how-to...er-performance/

https://www.sonicwall.com/support/knowledge...70505851231244/

that for ADSL, trying to fit packet inside ATM without ATM Padding.

Now we on Fiber, that solutions is not suitable.

GPON has fixed MTU 2000 bytes!

That is why I can use MTU 1500 on PPPoE (Maxis Fiber) and MTU 1508 Ethernet!

With MTU 1500 bytes, able to access website and server that have strict firewall (Block MTU less than 1500)

This post has been edited by Anime4000: Sep 11 2021, 02:10 AM

For me, i only manage MTU 1488 (beyond that it will reduce to default at 1480), using unifi btu/ont

Ok, finally.

This MTU 1480 this has been bugging me for years.

Looks like the issue is with Mikrotik's RouterOS.

Keeping everything else the same, same site same btu etc,

Using the TP Link ER605, I am able to get an MTU of 1492.
Proven by the fact that I can ping sites with packet size 1464.
1464+28 (ip and icmp headers)=1492.
Using my RB4011, MTU shows 1480, as expected.
Pinging sites with packet size of max 1452 suceeds.
packet size of 1453 fails.