Firefox: connection has timed out

[SamGuay]

To Reproduce

1. Open Firefox with add-ons OR all add-ons turned off.
2. Try to go to https://reservation.unf-montreal.ca/ or https://reservation.unf-montreal.ca/Web/schedule.php and wait for the page to load.

(Note: It does load and work on Chromium and Firefox Mobile.)

Actual behavior

After ~5 minutes of trying to load the page, Firefox results with a Problem loading page message and the page never appears (see screenshot)

Expected behavior

The page should load as expected.

Screenshots

System information

Operating system: Ubuntu 20.04
Browser: Firefox 93.0
Javascript enabled: Yes
Cookies enabled: Yes
Flash version: Not installed
Java version: Not installed
Websockets supported: Yes
WebGL supported: Yes
Language: en-CA

[bpinsard]

Thanks for the issue report.
Does that happen only on CRIUGM network, on WIFI only? Is that the same for other website (eg. dicom.unf-montreal.ca ). We had some weird network behavior reported by other users.

[SamGuay]

Does that happen only on CRIUGM network, on WIFI only?

🔴 CRIUGM-usagers wifi
🔴 wired network @ CRIUGM
🟢 my own LTE network

Is that the same for other website (eg. dicom.unf-montreal.ca )

It seems to be doing the exact same thing with dicom.unf-montreal.ca, etc. Working on Chromium but not FF.

[bpinsard]

I think I found the culprit. Firefox uses an external DNS over https internally, which in that case return the external IP address, instead of the internal one. If you disable the last option, it works.

[bpinsard]

It's because the CRIUGM firewall doesn't have hairpin NAT (or NAT loopback) which is a not-so-common option anyway, so external IP addresses are not accessible from the inside.

[SamGuay]

Oh wow, interesting! It now works like a charm with this option disabled!