From: tlhackque <firstname.lastname@example.org> To: email@example.com Subject: Re: Question about MTU and Wireguard and the current changes Date: Mon, 10 Jan 2022 15:56:07 -0500 [thread overview] Message-ID: <firstname.lastname@example.org> (raw) In-Reply-To: <email@example.com> [-- Attachment #1.1: Type: text/plain, Size: 1369 bytes --] On 10-Jan-22 15:37, firstname.lastname@example.org wrote: > Hi, > I run in some connection troubles between two wireguards host (one > running fedora 35, one arch linux). If I tried to transfer large files > through SSH (SCP or btrfs send/receive thorugh ssh through wireguard > tunnel) it stucks after a few byte and nothing transfered anymore. > > This happens in the last days, so probably an update on one or both > machines. I also saw, that there some changes on the MTU thing (If I > remember correctly, a per peer MTU is configurable) > > However. My first try was just set the MTU to a lower number (MTU = > 1200) and yes, scp works again. > Okay, so I did the good old ping test. "ping -M do -s $SIZE -c 1 > 172.16.0.2" with $SIZE increasing. And that surprised me. It works > until an Size of 36932 Bytes. Checked with wireguard and "MTU = 36932" > and yes, scp still working. > > Can somebody explain, why the old default setting of "65456" doesn't > work anymore but the MTU can set to much higher values as typical ones? > > Thanks > Henning > Guess: Fragmentation happens somewhere and fragments are blocked at your router/firewall/host. Blocking fragments is a common, if misguided, "security enhancement". A packet trace would provide the necessary clues in any case. Wireshark is a convenient way to get one. [-- Attachment #2: OpenPGP digital signature --] [-- Type: application/pgp-signature, Size: 840 bytes --]
prev parent reply other threads:[~2022-01-10 20:57 UTC|newest] Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-01-10 20:37 henning.reich 2022-01-10 20:56 ` tlhackque [this message]
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