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A simple question (hopefully) but with no clear answers when doing a Google Search. What is the MTU of VDSL (not VDSL2)? With ADSL it was 1492, but most ISPs added PPPoE/PPPoA headers reducing it to 1452, is this still the same when it comes to other types of DSL (including VDSL)?

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1 Answer 1

up vote 2 down vote accepted

You can check the MTU yourself using ping. Have a look at this page.

For Linux:

$ ping -c <packet_count> -M do -s <packet_size> <remote_ip>

For Windows:

ping -l <packet_size> -f <remote_ip>

If you receive an error similar to this:

Packet needs to be fragmented but DF set.

Then, your MTU has been exceeded. You can try a smaller value until get a different response.

You can check the PPPoE RFC. It says the maximum MTU is 1492 as you said.

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Whilst there is the trial and error method, here we have different VDSL providers and they may have different MTUs set on their internal routing equipment (this was the case with one ADSL2 ISP in particular), thus hindering this technique. I just wanted to know what the MTU of the standard is. –  Metalshark Nov 27 '10 at 11:17
    
@Metalshark: Check PPPoE standard RFC2516 –  Khaled Nov 27 '10 at 12:06
    
that makes sense, thank you –  Metalshark Nov 27 '10 at 12:09

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