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Bug #11291
closed
WireGuard MTU Can Flap between 1420 and 1500
Start date:
01/22/2021
Due date:
% Done:
100%
Estimated time:
Plus Target Version:
Release Notes:
Affected Version:
2.5.x
Affected Architecture:
Description
The default WireGuard MTU is typically 1420. However , I’ve observed cases where the wg interfaces will flap between 1500 and 1420. Explicitly configuring an MTU on the interface configuration fixes it
Updated by Christian McDonald almost 4 years ago
I've nailed down clear reproduction steps...assuming that you have a WG tunnel and it's corresponding wg interface assigned.
- Go to the WG interface configuration and click save and apply.
- Check Status > Interfaces and the WG interface will have an MTU of 1500
- Go to the VPN > Wireguard > Tunnel configuration and click save
- Check Status > Interfaces again and the WG interface will now have an MTU of 1420
This is obviously problematic and was discovered by OSPF adjacency issues because the remote end had a fixed MTU of 1420, which is the WG default. I've disable MTU mismatch detection on both ends for the time being.
Updated by Jim Pingle almost 4 years ago
- Status changed from New to In Progress
- Assignee set to Jim Pingle
Updated by Jim Pingle almost 4 years ago
- Status changed from In Progress to Feedback
- % Done changed from 0 to 100
Applied in changeset 8b9d2275015be7bf8febb1714f8a979d7c5f2beb.
Updated by Christian McDonald almost 4 years ago
Looks good, thanks for the quick update
Updated by Jim Pingle almost 4 years ago
- Status changed from Feedback to Resolved
MTU is stable on current snapshots. It's 1420 even after save/apply on an assigned interface.
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