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tl;dr given a Wireguard client and server with different MTU values, which value is used?

Given a Wireguard "client" with configuration file

[Interface]
MTU = 1440
...

and a Wireguard "server" with configuration file

[Interface]
MTU = 1420
...

which MTU value is used? In other words, is there a negotiation between them for a common MTU value?
Or does each side use exactly the MTU value it is given?

Kiran Kotturi
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JamesThomasMoon
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1 Answers1

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Both will be used, WireGuard does not negotiate MTU. The MTU value just tells the particular local WireGuard not to construct data packets larger than the value set.

user9517
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  • Is there a way, using for instance `iptables` to override the peer's `wireguard` MTU config on server side? – W.M. May 13 '23 at 09:03