Hi !

We are trying to get our heads around MTU.

Our Vigor 2860ac seems to default to an MTU of 1500.
Reading other explanations this seems to be too high, and fragmentation occurs.
I used ' ping -f -l 1472 http://www.dslreports.com ' and this seemed to be working, whereas the current setting of 1492 works but fragmentation 'seems' to be indicated i.e. we get a response of 'Packet needs to be fragmented but DF set'

So, I just want to unpack this a bit with three questions:
1 Am I right in thinking that the router is 'the only important' item to get the MTU right? Basically because everything has to travel through it?
2 Or do I need to 'worry' about the fact that I need to change it because the connections to the users are a mix of one ethernet and (usually 6 but) up to 15 wifi connections?
3 Finally do I need to adjust any of the Windows ver 7 or 10 settings?

We are on ADSL and slightly more than 2km from the exchange (using G.dmt Annex A), so we are usually connected at between 3.5-4.3 mbps.

Thanks in advance for any help.

T.

Just had a great reply from Draytek support... should have thought of them first..


Below is a guild on MTU settings for your router.

https://www.draytek.co.uk/support/guides/kb-vigor-mtu-2?highlight=WyJtdHUiXQ==

https://www.draytek.co.uk/support/guides/kb-vigor-mtu?return=8557614


In response to your questions:

1 Am I right in thinking that the router is 'the ONLY important' item to get the MTU right? is that because everything has to travel through it?

A>The MTU is important but its also crueshal to set the correct VPI, VCI, Modulation,protocol and Encapsulating Type for the router.

The DSL modem should also be set to default. This can also determine the right speed for your line.

2 Or do I need to 'worry' about the fact that I need to change it because the connections from the router to the users (max. total connections=16) are a mix of one ethernet and up to 15 wifi connections?

A>No you do not need to worry about this. Although larger MTU (Maximum Transmission Unit) may bring higher efficiency, but if the router's WAN MTU is too large, the packet will be fragmented when traversing, thus it's important to configure a proper MTU size to have better performance and avoid Internet access issue.

3 Finally do I need to adjust any of the Windows ver 7 or 10 settings?

A>No, you only need to adjust the MTU value on the router GUI.

Below is a link to other firmwares, that may improve your line speed.

http://www.draytek.co.uk/support/downloads


Vector1 Firmware 3.8.4.6

Vector2 Firmware 3.8.4.6 etc...

Excellent Draytek Support... very clear and right at my level.. Thank you.