Debugging a Google Compute Engine Proxy Server Refusing Connections - http

Hey so I have three GCE instances set-up which all run the same code. They're cloned from the same snapshot so I'm pretty positive that they're exactly the same.
For some reason, only one of these GCE instances is able to receive connections from external sources. The other two can't. I keep getting a "Connection timedout" error in Firefox.
These instances all have the same network-tags, so they should have the same firewall rules. That is, if you're hitting this problem too, make sure you have the right firewall rules set in the networking tab of your google-cloud center before reading on.
Since they're running the same code and have the same ports open, I have no idea what the problem could be, or how to figure out what it might be.
I was wondering what the best way to debug this might be? I believe they were working earlier but now are no longer working.

Rebooting the instance seemed to fix this. This is not an adequate solution however. I'll update my answer over the coming weeks if it happens again.

Related

Netflix/Prime not being able to login/connect after sometime

When I just start the pfSense, both Netflix and Prime works fine, I can login and watch contents, but after one day or so of my pfSense being online, I just can't login to those video streaming services anymore.
For Netflix I get the "NW-2-5" error and for Prime I receive a message saying there are connectivity issues. Then I have to reboot my pfSense and after that everything is working fine for, again, one day or so.
My guess is this has nothing to do with the firewall rules, as it works for one day or so, but just in case I took a screenshot of it, in the Block separator I isolated my other VLANs (Home, VPN BR and Guest):
I'm still learning about how to configure my pfSense correctly and I hope this is just a silly configuration mistake.
Any suggestion about what I should change or check in the configuration?

How do I resolve an "Arg_NullReferenceException" error when trying to connect through CheckPoint VPN?

I use CheckPoint VPN to log in to my place of work's servers to work remotely. The VPN has been working (mostly) fine all year, and I haven't changed any of the settings, but this morning, when I tried to log in, it's giving me the "Arg_NullReferenceException." I can't seem to find anything on this particular error on google.
I have tried restarting my computer, because it's not the first issue I've had with CheckPoint VPN (though it is the first time I've seen that error message), and a restart usually resolves whatever issue I'm having. I've also tried creating a new connection with the same settings, but I'm getting the same error with that one, too.
I'm not entirely sure what other information I would need to provide. I'm also not sure if it's a problem on my end, or on the company servers. I have already emailed tech support, but I thought I should be thorough.
This is a known issue. I have been jumping through hoops trying to get the capsule client to work. Raise a ticket with TAC if you have support. If not then you can download the E86 Endpoint connect client and run it. That has been my work around for this issue.
They just issued an update to the Capsule via the Microsoft Store. It seems one of the recent Windows Security Update broke the L2TP protocol within windows.

Amazon EC2 Instance - only accepting single connections?

I'm having a lot of trouble with an EC2 instance and I can't figure out what's going on. We're using it as a web server and it seems to work fine for single connection stuff - loading a simple page, RDP connection, ping etc. But as soon as a single client computer has more than one connection active with the server (a good example is if I try to browse the web site while I'm also logged into the server via RDP) the whole connection becomes incredibly unstable.
The biggest most annoying consequence of this is that the ASP.NET site that we're running consistently fails to load some pages since those pages use more than one connection. This wasn't a problem up until a few days ago when we were forced to migrate to different hardware because our hardware was apparently being retired by Amazon. Ever since then it's been tricky like this. Is it possible that there's a kink in Amazon's network and that it could potentially be resolved by stopping and starting the instance (and thus getting a different server?)
It turns out the problem was an underlying issue on Amazon's end. They investigated the issue and found a problem that they're correcting. I hope I haven't wasted too much StackOverflow brainpower with this dead-end of a question!

How to find where a connection is failing

I have a website running a basic ASP.NET application that is mostly used from a single location, which is my client's office. The server is at a high-class datacenter.
Whenever I've been testing or using my application from outside their office I have consistently good connections but from their office the connection seems inconsistent. Sometimes requests just don't seem to make it to the server from the browser. I'm not familiar with the network hardware in the office, but they do have a T1 connection which should always be on.
I've tried ping and tracert and everything looks normal. When running Firebug during a failed request the request shows up in the log, then just sits there without showing it is sending any data, eventually it times out.
My question is, what tools can I use to diagnose this connection problem and start to narrow it down to a specific cause so I can fix it? Its an intermittent problem so a long running tool would probably make more sense, if there is any available.
Thanks for any help.
All of your standard ping and traceroute tools are probably your best bet. I'm not understanding though, where is the site located?
If you open command prompt, run ping -t aspwebsiteurl.domain <- will show if there is packet loss.
From command prompt again, tracert aspwebsiteurl.domain <- will show you what route the packet is taking to get the site. May also show you if there is one particular hop that is giving you the hickup.
Is there a proxy between the office and the datacenter that could be causing issues?
Also you could try Wireshark to try to debug the problem in more detail.
Speed Test - Internet Network Connection Speed may be of some help with some links to test out the connection at the client's office to see how well it works.
Another question is how far away is the client and the datacenter? If one is in New York and the other in Los Angeles then the distance apart may be a factor. Also, have you examined any possible DNS issues?

Is there a technical reason for applications to hang on DNS lookups?

If I try to quit Firefox when it's "Looking up domain.com..." it beachballs (hangs), goes into "not responding" status, then finally quits. It does this without fail.
This is on Mac with the latest FF, but it's always been this way for me, even on Windows with FF and I've noticed it with other applications.
Is there any technical reason why this can't be handled better?
No. You can use threads or even seperate processes to do this asynchronously (non-blocking). This is just poorly written software.
Aside from that, I don't have this particular problem with FF...
You should check bugzilla.mozilla.org to see if there are any recent bugs regarding the DNS service. Historically, this type of problem is very rare in Firefox and other mozilla based products, but there have been times where specific problems caused the DNS service to die or wait until a timeout.
The other important question is: are you sure it is DNS? A packet trace or necko debug logs might be useful. The way the status bar works, what is says is not necessarily what is keeping it from quitting.
There is a bug report for this problem. It has been around since at least 2004.

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