As a Linux sysadmin, you know that the general consensus is to blame every problem on infrastructure, which is your realm. Network engineers, our arch nemeses (kidding), always tell us that, "It's not a network problem." I really hate hearing those words because it means that now the focus is on me, my operating systems, and my hardware. Rather than rely on the word of my sworn enemy (kidding again) to tell me where the problem is, I can proactively investigate the network for myself. The mtr
utility allows me to do it without bothering anyone else or getting stewed during an all-hands, troubleshooting conference call. The mtr
command is a simple but effective network analysis and troubleshooting tool. This brief introduction will get you started.
The following description is from the mtr
command's package information.
Mtr is a network diagnostic tool that combines ping and traceroute into one program. Mtr provides two interfaces: an ncurses interface, useful for using Mtr from a telnet* session; and a GTK+ interface for X (provided in the mtr-gtk package).
*Obviously, this description is somewhat outdated. Replace 'telnet' with SSH.
Why mtr?
You might wonder why I'm writing about a utility called My Traceroute (mtr
) when there is traceroute
, ping
, netstat
, ip
, and other tools lying around that can help with troubleshooting network connectivity. Well, mtr
is a little different. It is analogous to the top
command in that it refreshes on its own and gives you a live look at network response and connectivity.
Installing mtr
If you don't have mtr
, which lives in /usr/sbin
, install it the usual way with YUM or DNF. The mtr
command is included in the base repository.
$ sudo yum -y install mtr
or
$ sudo dnf -y install mtr
Using mtr
The mtr
command is simple to use. There are multiple options for using mtr
, but these are the most useful for my environment. Feel free to explore all of mtr's options. You can't do any damage to your system, or anyone else's, with this command. The mtr
command does not create security issues for you, so use it freely.
[ You might also enjoy: 5 Linux network troubleshooting commands ]
IPv4 only
My favorite way to use mtr is with the 'IPv4 only' switch (-4
). The output is limited to IPv4 addresses. This option (switch) doesn't prevent DNS lookups. In other words, if the host resolves to a name, you'll probably see the DNS name rather than just the IPv4 address.
Since mtr
updates in real-time, the following video provides a better illustration of how it works.
mtr
continues to refresh until you press q
to quit. As you can see, there was some packet loss at one of the hops. It doesn't seem significant, but that's the type of information you need to see when troubleshooting a network problem or potential network problem.
You can also tell mtr
to report IP addresses rather than DNS resolved names by using the (-b
) option. For this example, I've combined IPv4 only and IP addresses. This is the way I use mtr
. Here's how it looks at the command line and in real-time:
$ mtr -4b google.com
IPv6
On my system, it seems that IPv6 is the default option, which I don't like, so I always specify IPv4.
$ mtr google.com
And one final real-time display just for fun.
[ Free cheat sheet: Get a list of Linux utilities and commands for managing servers and networks. ]
Wrap up
I think you can see from these demonstrations that mtr
is a valuable command to have in your sysadmin toolbox. It isn't a superfluous command or a "boutique" command that you only use once a year. This is one you'll use over and over again when one, or more, of your users, says "The Internet is slow." A quick mtr
will show you where the problem is—if it's a network problem. Which, of course, we know it never is—until it is.
À propos de l'auteur
Ken has used Red Hat Linux since 1996 and has written ebooks, whitepapers, actual books, thousands of exam review questions, and hundreds of articles on open source and other topics. Ken also has 20+ years of experience as an enterprise sysadmin with Unix, Linux, Windows, and Virtualization.
Follow him on Twitter: @kenhess for a continuous feed of Sysadmin topics, film, and random rants.
In the evening after Ken replaces his red hat with his foil hat, he writes and makes films with varying degrees of success and acceptance. He is an award-winning filmmaker who constantly tries to convince everyone of his Renaissance Man status, also with varying degrees of success and acceptance.
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