Wireguard and MTU

Ibrahim Tachijian barhom at netsat.se
Wed May 31 11:31:35 CEST 2017

I understand that by default wireguard chooses an MTU of 1420.
The way that I have setup wireguard now is that I have a router (running
LEDE/openwrt) connecting to wireguard running on an arch server.

I then set the default gw to go through wireguard and properly do iptables
nat masquerading so that the only ip inside the tunnel is the ones in
Basically all my traffic from the router (lede/openwrt) now flows over
wireguard and then to the internet.

   - Router -> wireguard -> Internet
      - working good because the MTU is properly set to 1420.
   - Wifi Client -> Router -> wireguard -> internet
      - Not working properly because of MTU is set at 1500 at wifi/wired
      dhcp clients.

How do we propose that we advertise the correct MTU that the NAT clients of
the router should use? Is there any other way to solve this issue?


*Ibrahim Tachijian*

CEO Net Sat AB
Mobile: +46723321377
barhom at netsat.se


*Net Sat ABC/O Jayway AB*Klara Östra Kyrkogata 2B, 1TR, 111 52 Stockholm,
Office: +46 (0)8 408 394 53
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