From: Roman Mamedov <rm@romanrm.net>
To: "STR ." <strykar@hotmail.com>
Cc: "wireguard@lists.zx2c4.com" <wireguard@lists.zx2c4.com>
Subject: Re: Help calculate MTU, ISP's 1448
Date: Thu, 28 Feb 2019 23:49:13 +0500 [thread overview]
Message-ID: <20190228234913.61927412@natsu> (raw)
In-Reply-To: <DM6PR12MB3401FF1DE04A62EAD84F2C74BB7B0@DM6PR12MB3401.namprd12.prod.outlook.com>
On Tue, 26 Feb 2019 12:39:50 +0000
"STR ." <strykar@hotmail.com> 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
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next prev parent reply other threads:[~2019-02-28 18:49 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-26 12:39 STR .
2019-02-28 18:49 ` Roman Mamedov [this message]
2019-02-28 19:56 ` Denis Kisselev
2019-02-28 20:56 ` Derrick Lyndon Pallas
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