From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.zx2c4.com (lists.zx2c4.com [165.227.139.114]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id E5DBAEE49B3 for ; Wed, 23 Aug 2023 16:20:01 +0000 (UTC) Received: by lists.zx2c4.com (ZX2C4 Mail Server) with ESMTP id 45d67ef2; Wed, 23 Aug 2023 16:15:47 +0000 (UTC) Received: from len.romanrm.net (len.romanrm.net [91.121.86.59]) by lists.zx2c4.com (ZX2C4 Mail Server) with ESMTPS id 2c27ad12 (TLSv1.3:TLS_AES_256_GCM_SHA384:256:NO) for ; Wed, 23 Aug 2023 16:15:45 +0000 (UTC) Received: from nvm (nvm2.home.romanrm.net [IPv6:fd39::4a:3cff:fe57:d6b5]) by len.romanrm.net (Postfix) with SMTP id 1ED2D40118; Wed, 23 Aug 2023 16:15:45 +0000 (UTC) Date: Wed, 23 Aug 2023 21:15:44 +0500 From: Roman Mamedov To: blurt_overkill882@simplelogin.com Cc: wireguard@lists.zx2c4.com Subject: Re: [WireGuard] Header / MTU sizes for Wireguard Message-ID: <20230823211544.7f3252ec@nvm> In-Reply-To: <169230331253.7.2936868369217934671.167170975@simplelogin.com> References: <169230331253.7.2936868369217934671.167170975@simplelogin.com> X-Mailer: Claws Mail 3.11.1 (GTK+ 2.24.31; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-BeenThere: wireguard@lists.zx2c4.com X-Mailman-Version: 2.1.30rc1 Precedence: list List-Id: Development discussion of WireGuard List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: wireguard-bounces@lists.zx2c4.com Sender: "WireGuard" On Thu, 17 Aug 2023 20:14:52 +0000 blurt_overkill882@simplelogin.com wrote: > I see here[1] that if you're using IPv4 exclusively, you can get away with > an MTU of 1440. If my client only has IPv4 internet, however the server > issues an IPv6 address for use by the client, can the client still use 1440 > without fragmentation, or must the client use 1420, because even though > their connection is IPv4, they are issued an IPv6 address within the tunnel? > > [1] https://lists.zx2c4.com/pipermail/wireguard/2017-December/002201.html Yes they can. This is only affected by whether or not WG itself runs over v4/v6, not whether you use v4 or v6 inside WG. Be aware though that some residential Internet connections use MTU-reducing tunnels for ISP authentication. The most popular one would be PPPoE with 8 bytes that you need to substract, but there also can be L2TP or PPTP with larger overheads. -- With respect, Roman