Netgate Discussion Forum
    • Categories
    • Recent
    • Tags
    • Popular
    • Users
    • Search
    • Register
    • Login

    MTU inconsistent local and remote

    Scheduled Pinned Locked Moved OpenVPN
    1 Posts 1 Posters 1.7k Views
    Loading More Posts
    • Oldest to Newest
    • Newest to Oldest
    • Most Votes
    Reply
    • Reply as topic
    Log in to reply
    This topic has been deleted. Only users with topic management privileges can see it.
    • M
      M0L50N
      last edited by

      Hi,

      I always have this Warning when I connect iphone or android to OpenVPN server :

      WARNING: 'link-mtu' is used inconsistently, local='link-mtu 1569', remote='link-mtu 1553'

      I tested to find my max MTU from the internet connexion the OpenVPN client with different ping test to found the max MTU is 1472
      ping -n 1 -l 1472 -f 8.8.8.8

      I tried to adjust the MTU (always on both side server and client) by adding both this options : "tun-mtu 1472". The MTU change when I'm connecting but again, the MTU isn't the same on both side and its not 1472 :
      WARNING: 'link-mtu' is used inconsistently, local='link-mtu 1523', remote='link-mtu 1527'

      I had some authenticate/decrypt packet error, I switched to TCP and that seems to resolved my problem, but this warning continue to appear in logs.

      I've done some research on the internet, a lot people talk about change parameter (tun-mtu, link-mtu) some people said that's not a problem (false alarm) but I dont think, I think VPN is really inconsistent and I got some disconnect because that.

      Thanks for any suggestions.

      1 Reply Last reply Reply Quote 0
      • First post
        Last post
      Copyright 2025 Rubicon Communications LLC (Netgate). All rights reserved.