How to diagnose network connectivity issues

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Please note that, sometimes your network administrator or your ISP may disable the ICMP protocol needed for these types of check to work. It doesn't mean service is down but you need to perform further diagnostics using tools such as Telnet. A detailed discussion of such diagnostics is beyond the scope of this article. However, you can find the basic use of Telnet in this article.

 Windows

Step 1: Check the IP/Ports

This article shows you how to do it: How to check if Teramind IP addresses/hosts and ports are reachable.

Step 2: Use the Ping command

Typically the Ping command is used to check some internet server availability and measure latency (a time gap between a request from a client and an answer from a server).

The basic syntax for the Ping command is:

ping <hostname/IP>

The output from the Ping command may look something like this:

>ping tera.teramind.co

Pinging tera.teramind.co [85.195.72.195] with 32 bytes of data:
Reply from 85.195.72.195: bytes=32 time=39ms TTL=54
Reply from 85.195.72.195: bytes=32 time=40ms TTL=54
Reply from 85.195.72.195: bytes=32 time=39ms TTL=54
Reply from 85.195.72.195: bytes=32 time=39ms TTL=54

Ping statistics for 85.195.72.195:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 39ms, Maximum = 40ms, Average = 39ms

If you see a message like Request timeout, it means some packets are dropped and your network connection is not very well. If they're all timed out it means either ICMP protocol is closed or server is unavailable from your location and you need to test it with telnet/nmap/Test-Netconnection etc. 

Also you need to pay an attention on the reply time. In the example above, it's about 39 milliseconds - which is very good. Compared to that, a trip time of 100 milliseconds or above means you may have a slow network connection or other issues between your PC and the server. There can even be issues with your ISP.

Step 3: Use the Tracert/Traceroute tool

While Ping allows you to quickly check if a server is reachable and they delay between requests, Tracert finds the exact route taken to reach the server and time taken by each step (hop/node). In essence, it provides you with more diagnostics information.

The basic syntax for the Tracert command is:

tracert -d <hostname/IP>

The -d switch prevents tracert from attempting to resolve the IP addresses of intermediate routers to their names. This can speed up the display of tracert results.

The output from the Tracert command may look something like this:

>tracert -d tera.teramind.co

Tracing route to tera.teramind.co [85.195.72.195]
over a maximum of 30 hops:

1 2 ms 1 ms <1 ms 192.168.0.1
2 2 ms 2 ms 2 ms 192.168.126.1
3 1 ms 1 ms 2 ms 192.168.253.25
4 1 ms 2 ms 2 ms 192.168.253.26
5 2 ms 2 ms 2 ms 109.95.77.195
6 3 ms 3 ms 3 ms 87.245.229.205
7 36 ms 49 ms 35 ms 87.245.232.233
8 39 ms 38 ms 41 ms 80.81.192.239
9 39 ms 40 ms 38 ms 87.230.115.5
10 43 ms 49 ms 42 ms 85.195.113.8
11 43 ms 39 ms 42 ms 85.195.72.195

Trace complete.

In this example, we can see that the reply time on node 87.245.232.233  has a "sharp spike" indicating an issue with that node.

Step 4: Use the Windows Event Viewer

You can also use Windows' built-in Event Viewer to capture a log of when Internet connectivity is lost.

To do so:

  1. Open the Event Viewer application
  2. From the panel on the left, navigate to: Applications and Services Logs > Microsoft > Windows > UniversalTelemetryClient > Operational item from the list on the right-side panel.
  3. From the Action menu on top, select Filter current log... option (note that, you may have to click on the Operational window to make it active. Otherwise, you may not see the filter option).
  4. Enter 55 in the <All Event IDs> field to filter only the internet connectivity items:

mceclip0__3_.png

  1.  In the General tab it will show "Is the Internet available: false" every time the internet drops:

mceclip1__1_.png​​

click to enlarge

You can compare those entries to the times when the Agent shows a disconnected or reconnecting status (in the case of a Revealed Agent) to see if they match and that will indicate the computer was experiencing a loss of connectivity rather than an issue specific to the agent.

MacOS

  • You can use the traceroute command the same way you would use the tracert on Windows (see above).
  • Use the ncat command:
nc -zv <hostname> <port>

Or,

nc -v <hostname> <port>
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