The sys admin's daily grind: ASN
Charly's Column – ASN
When digging into BGP routing information, Charly avoids the highway through parameter hell thanks to the ASN tool. In addition to a system's AS number, ASN delivers other information, such as its peering partners upstream and downstream.
Every admin knows how to deal with IP addresses. Unfortunately, IPs never turn up alone. They belong to a network, and the network is almost always assigned to an autonomous system (AS), which uses the Border Gateway Protocol (BGP) to exchange routing information.
There is a simple way to find out which AS a particular individual IP belongs to. By way of an example, the following is the IP address of Computec Media's web server, www.computec.de. The associated IP address 62.146.104.133 can be discovered using dig or by simply pinging.
I then feed this IP address to a tool named ASN [1]. The shell script aggregates the output of several other tools and presents the results in a clear-cut way. It has a number of dependencies that vary depending on the distribution you are using. What exactly needs to be installed for ASN to work is explained in a separate section on the tool's GitHub page.
The output from calling asn 62.146.104.133 reveals that the IP address in question belongs to network 62.146.0.0/16 and AS15598 (Figure 1). AS numbers (ASN) are unique worldwide and are assigned by the Internet Assigned Numbers Authority (IANA).
A second call with the ASN as a parameter (asn AS15598) provides a variety of information about the AS, such as the upstream and downstream peering partners (Figure 2). In addition, you can see which other networks are assigned to this AS besides the already known 62.146.0.0/16 and which paths the data packets take from the local AS to the destination (Figure 3).
All this information could be obtained in other ways, but thanks to ASN, I was able to save time and avoid a detour through parameter hell.
Infos
The Author
Charly Kühnast manages Unix systems in a data center in the Lower Rhine region of Germany. His responsibilities include ensuring the security and availability of firewalls and the DMZ.
Buy this article as PDF
(incl. VAT)
Buy Linux Magazine
US / Canada
UK / Australia
Subscribe to our Linux Newsletters
Find Linux and Open Source Jobs
Subscribe to our ADMIN Newsletters
Support Our Work
Linux Magazine content is made possible with support from readers like you. Please consider contributing when you’ve found an article to be beneficial.
News
-
Thousands of Linux Servers Infected with Stealth Malware Since 2021
Perfctl is capable of remaining undetected, which makes it dangerous and hard to mitigate.
-
Halcyon Creates Anti-Ransomware Protection for Linux
As more Linux systems are targeted by ransomware, Halcyon is stepping up its protection.
-
Valve and Arch Linux Announce Collaboration
Valve and Arch have come together for two projects that will have a serious impact on the Linux distribution.
-
Hacker Successfully Runs Linux on a CPU from the Early ‘70s
From the office of "Look what I can do," Dmitry Grinberg was able to get Linux running on a processor that was created in 1971.
-
OSI and LPI Form Strategic Alliance
With a goal of strengthening Linux and open source communities, this new alliance aims to nurture the growth of more highly skilled professionals.
-
Fedora 41 Beta Available with Some Interesting Additions
If you're a Fedora fan, you'll be excited to hear the beta version of the latest release is now available for testing and includes plenty of updates.
-
AlmaLinux Unveils New Hardware Certification Process
The AlmaLinux Hardware Certification Program run by the Certification Special Interest Group (SIG) aims to ensure seamless compatibility between AlmaLinux and a wide range of hardware configurations.
-
Wind River Introduces eLxr Pro Linux Solution
eLxr Pro offers an end-to-end Linux solution backed by expert commercial support.
-
Juno Tab 3 Launches with Ubuntu 24.04
Anyone looking for a full-blown Linux tablet need look no further. Juno has released the Tab 3.
-
New KDE Slimbook Plasma Available for Preorder
Powered by an AMD Ryzen CPU, the latest KDE Slimbook laptop is powerful enough for local AI tasks.