[notes] CDN problem on umich.edu eduroam network

(Isaiah Norton) #1

Some users at University of Michigan cannot access the Discourse CDN for some site resources. Here’s a debugging conversation (I followed up by email up from this topic).

They can’t connect to these other Discourse sites either:


They see a browser error loading resource, and can’t ping the CDN. Does this ring any bells?


On my side, I tried with Safari and Chrome and I have the same result. I can open discourse.org and the other hosts I tried.

What happens is the web page loads first the text in a browser tab:

Then the page stays blank and after few minutes it sends a timeout error in the chrome console:


Ok, that helps to narrow it down a little bit. Can you ping discourse-cdn-sjc1.com/standard2? Is there any ad-blocker installed on these computers? There’s a bug report that sounds kind of similar, where some software was blocking the Discourse CDN due to false positive:


Might be happening on your network if they use a similar heuristic or list.


That ping is not working.

There is an ad-blocker in my Chrome but not in Safari, and I tried to disable the ad-blocker and the issue is still the same.

Then, why can I access the website with my smartphone on the same network, would it be linked to the browser?


Since you can’t ping the CDN at all, it’s probably not the browser. That seems like it might be a block at the institution level (since you said multiple computers), or at least local firewall.

I think the ones I originally linked are mostly business hosting, so they might be hitting a different CDN. Can you try these, they’re on the same plan as Slicer and hits a similar CDN for me:


Then, why can I access the website with my smartphone on the same network, would it be linked to the browser?

Assuming you are connected to wi-fi, but also have cell service, maybe it falls back to unblocked cell network if a request fails – I’m not sure what the request resolution rules are on various phones.


When we tried on laptops, we used eduroam, so not really specific. But, on the computers plugged on the department wifi it’s working fine.


Ok I missed that the first time: so just to clarify

  • the problem is only on the wifi network called eduroam?

I think you need to contact the university IT in this case – looks like "4HELP@umich.edu" (from the site above). I don’t think there is much Discourse can do if the CDN is blocked on that specific wireless network. From what I can tell, eduroam is just an authentication provider, so university IT controls the configuration.

It looks like someone else saw weird issues with eduroam too, but no follow-up on any resolution:


(Isaiah Norton) #2


I tried with MWireless and eduroam => not working but with MGuest => working. So, the solution is to contact IT or to switch to a non-blocking network to access the discourse.

So, they are going to follow-up with university IT, because there is nothing we or Discourse can do about local network settings.