From 0ef7d0b3e5b6d4ab713f7f2b73df6f77fc0114e1 Mon Sep 17 00:00:00 2001 From: Spike Curtis Date: Wed, 23 Apr 2025 10:00:33 +0400 Subject: [PATCH] docs: correct low MTU troubleshooting language (#17468) Fixes docs troubleshooting language around low MTU. In fact, we see conenctions hanging rather than just showing low performance, since packets are dropped rather than fragmented. --------- Co-authored-by: Edward Angert Co-authored-by: EdwardAngert <17991901+EdwardAngert@users.noreply.github.com> --- docs/admin/networking/troubleshooting.md | 23 ++++++++++++++++++----- 1 file changed, 18 insertions(+), 5 deletions(-) diff --git a/docs/admin/networking/troubleshooting.md b/docs/admin/networking/troubleshooting.md index deab8bdc15..15a4959da7 100644 --- a/docs/admin/networking/troubleshooting.md +++ b/docs/admin/networking/troubleshooting.md @@ -95,14 +95,27 @@ the NAT configuration, or deploy an internal STUN server. If a network interface on the side of either the client or agent has an MTU smaller than 1378, any direct connections form may have degraded quality or -performance, as IP packets are fragmented. `coder ping` will indicate if this is -the case by inspecting network interfaces on both the client and the workspace -agent. +might hang entirely. -If another interface cannot be used, and the MTU cannot be changed, you may need -to disable direct connections, and relay all traffic via DERP instead, which +Use `coder ping` to check for MTU issues, as it inspects +network interfaces on both the client and the workspace agent: + +```console +$ coder ping my-workspace +... +Possible client-side issues with direct connection: + + - Network interface utun0 has MTU 1280 (less than 1378), which may degrade the quality of direct connections or render them unusable. +``` + +If another interface cannot be used, and the MTU cannot be changed, you should +disable direct connections and relay all traffic via DERP instead, which will not be affected by the low MTU. +To disable direct connections, set the +[`--block-direct-connections`](../../reference/cli/server.md#--block-direct-connections) +flag or `CODER_BLOCK_DIRECT` environment variable on the Coder server. + ## Throughput The `coder speedtest ` command measures the throughput between the