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 X-Spam-Level: X-Spam-Status: No, score=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B43BEC43381 for ; Thu, 28 Feb 2019 18:49:20 +0000 (UTC) Received: from krantz.zx2c4.com (krantz.zx2c4.com [192.95.5.69]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 40D52218B0 for ; Thu, 28 Feb 2019 18:49:20 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 40D52218B0 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=romanrm.net Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=wireguard-bounces@lists.zx2c4.com Received: from krantz.zx2c4.com (localhost [IPv6:::1]) by krantz.zx2c4.com (ZX2C4 Mail Server) with ESMTP id e4f923ae; Thu, 28 Feb 2019 18:39:35 +0000 (UTC) Received: from krantz.zx2c4.com (localhost [127.0.0.1]) by krantz.zx2c4.com (ZX2C4 Mail Server) with ESMTP id c9e75145 for ; Thu, 28 Feb 2019 18:39:33 +0000 (UTC) Received: from len.romanrm.net (len.romanrm.net [91.121.75.85]) by krantz.zx2c4.com (ZX2C4 Mail Server) with ESMTP id 17cf625e for ; Thu, 28 Feb 2019 18:39:33 +0000 (UTC) Received: from natsu (unknown [IPv6:fd39::e99e:8f1b:cfc9:ccb8]) by len.romanrm.net (Postfix) with SMTP id BDD1820394; Thu, 28 Feb 2019 18:49:13 +0000 (UTC) Date: Thu, 28 Feb 2019 23:49:13 +0500 From: Roman Mamedov To: "STR ." Subject: Re: Help calculate MTU, ISP's 1448 Message-ID: <20190228234913.61927412@natsu> In-Reply-To: References: MIME-Version: 1.0 Cc: "wireguard@lists.zx2c4.com" X-BeenThere: wireguard@lists.zx2c4.com X-Mailman-Version: 2.1.15 Precedence: list List-Id: Development discussion of WireGuard List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: wireguard-bounces@lists.zx2c4.com Sender: "WireGuard" On Tue, 26 Feb 2019 12:39:50 +0000 "STR ." wrote: > I have Fiber to our apartment complex basement, from there Cat6 runs to > each apartment. The ISP/apartment service provider suggests an MTU of > 1448, which I set for the PPPoE interface on my OpenWRT router. It could be that your ISP meant this as the pre-PPPoE MTU, so 1448 on ethX link, but 1440 inside PPPoE. > I read > https://lists.zx2c4.com/pipermail/wireguard/2017-December/002201.html > which comes to (assuming 1500 byte MTU) to 60 bytes (IPv6) to 80 bytes less to account for Wireguard protocol overhead. > > Using this info, I tried an MTU of both (1448-80=1368) and (1448- > 60=1388). > As my ISP assigns only IPv4, I expected an MTU of 1388 to work, which I > set on the Wireguard interface in OpenWRT. > > However, when set to 1388, almost everything works except any Google > related sites like Maps, Gmail, YT etc. > When set to 1368, everything works and it's the way I have it setup > right now. Try 1380 for a bit. > What am I missing here? > Why won't Google sites load via my WG VPN when the MTU is set to 1388? > > If it helps, I host the WG server on Google's cloud platform and was > informed that GCP has an MTU of 1460 bytes. Are you setting the same (lower of the two maximums) MTU on both ends of the wireguard tunnel? (You should) -- With respect, Roman _______________________________________________ WireGuard mailing list WireGuard@lists.zx2c4.com https://lists.zx2c4.com/mailman/listinfo/wireguard