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justicefreed / README.md
Created May 13, 2025 17:21
Fix VLAN MTU Bug on OSX (eg HTTPS pages won't load)

Bug / Issue Description

OSX does not correctly fragment packets on VLAN virtual interfaces for default MTU settings. Additionally, manually setting interface MTU settings do not always persist across interface disconnection, sleep, and reboot in some OSX versions.

What is supposed to happen

  1. A virtual interface of type "VLAN" has been created and attached to a parent interface
  2. You try and make a network request of any kind using that VLAN / virtual interface that expects a response larger than 1472 Bytes, like an HTTPS web page (HTTP may not exceed this).
  3. Because the request is larger than the interface MTU, it is split into fragments. Each fragment should be at most the size of the parent MTU MINUS the 4 bytes for the VLAN header(s)