You have experienced various problems when connecting to a resource on the Internet, for example, such as high latency or no availability at all. These problems can be caused by incorrect operation of the intermediate devices in the network as host or end user
The first step to fix the difficulty is to check the ping node or perform a route trace. Tracing can help you determine at what point in the path the issue occurs.
Tracing is a program that checks the route of the data on the way to the server and gives you structured data about the route and the errors that occurred.
How does tracing work?
The tracing process has its own peculiarities for different operating systems. The main difference is in the command itself: for Windows it is called tracert, and for Linux and MacOS it is called traceroute.
The TRACERT command uses the ICMP protocol, and sends the TTL echo packets one at a time by increasing their size and tracing their path. TTL indicates the lifetime of the packet. In the beginning the program sends TTL-1, which is 1, it goes to the first node, coming to him reduced by one and sent back. The response from the first node is written on the first line, recording the node address and the travel time. After that, a request is sent with TTL-2, which is increased by one compared to TTL-1. Then it is sent to the first node, where it is decreased by one, then sent to the second node, where it is already equal to zero, and therefore goes back. This process continues until the request reaches the server.
The TRACEROUTE command works on the basis of sending UDP fragments and receiving a port availability/unreachability message. The host generates a UDP fragment, encapsulates it in an IP packet and sets TTL=1. The transit node responds to this icmp packet with a message about the end of packet lifetime. The traceroute utility receives this message and indicates the source address of the ICMP packet as the address of the first hop. The process then repeats with the TTL of the packet incremented. It’s pretty much the same as in tracert. During the tracing process, the UDP destination port number will be incremented at each attempt (33 434, 33 435, etc). It may happen that the destination port is open. In this case server will send e.g. TCP ACK to host initiator if it uses TCP SYN packets for tracing which will be also a trigger to end tracing. In this article, we’ll look at how to trace on Windows, Linux, and MacOS.
Tracing on Windows
In order to perform tracing, you need to do the following steps:
1) First, go to the Start menu and type «Run» in the search bar. Or you can use a shortcut to call the program by pressing «Win + R» on your keyboard. The following «Run Program» window will appear in front of you.
2) In the «Run the program» window enter «cmd».
3) Now you have the Windows command line in front of you, where you enter «tracert_server_addresses». You may specify both IP address and domain name of the server being checked; it is obligatory to put these data after «tracert» command and press «Enter» key.
After these steps, you will get the analysis data. The tracert command outputs the data in the form of a table. The table will contain the data in the following order: node sequence number, round-trip delay (time), node name, node IP address.
Tracing on Linux
Tracing in Linux is performed as follows:
- Press the key combination «Ctrl+Alt+T» on your keyboard to call the command window.
- Type «Terminal» in the search box
- As remembered earlier, traceroute on Linux is invoked with the command «Traceroute». Accordingly, you need to type in the command line «traceroute addresses_server», with a space after Traceroute you can type the IP address of the server or the domain name.
The command will bring you a table of data, which will consist of the serial number of the router or in other words node, node name, node IP address, and round-trip delay.
Tracing on macOS
To start tracing on macOS:
- In Spotlight, find «Network Utility» and run it.
- Now find the «Traceroute» tab in the «Network Utility».
- In the «Traceroute» tab, enter the server IP address or domain name in the input field and click «Trace» button.
The Traceroute command outputs the data in the same order as for Linux.
What asterisks (*) in tracing result mean
Sometimes the tracing program generates asterisks (*) in one or several lines at the end of analysis. Asterisks often mean one of the nodes is not responding. There are cases when the asterisks in the line are displayed due to the fact that the server may have a Firewall, which blocks «unnecessary» packets and lets only «real» ones through. This is done to reduce the load. Accordingly, this is not a problem and your site will open correctly.
Let’s consider two situations: if tracing produces asterisks instead of one line and the following lines are output correctly, and tracing finishes successfully, then everything is OK — the node has passed data on; if tracing produces asterisks instead of one line and the following lines are output with asterisks before tracing ends — this means there is a issue with the node.
In the case of Linux and MacOS, the second situation is not so unambiguous. Since these operating systems trace on ports using the UDP protocol and ports in the range [33 434; 33 534], often, firewalls simply block ports in this range for security reasons. But it is very easy to check for errors — to do it, you need to make a trace using ICMP packet, just adding option -I, specifying it before the IP address or domain name of the server. If you still have asterisks after the trace, it means that the error occurred at some part of the path.
Additionally, you can use PathPing command, which allows you to detect spots with packet loss on each router.
ADAMANT Tech Support
If you have issues, like delay or connectivity, you can contact our specialists for help. To do so, please have the following information ready:
- Server name, IP address;
- Description of the problem;
- Date/time when the problem occurred;
- File with the trace results; it is desirable to trace the route from the consumer to the final resource and in reverse order if possible;
- Additionally we can provide ping or MTR results.
Our specialists will gladly help you to solve your problem.