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).
Figure 1: A first call reveals the ASN, among other things.
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).
Figure 2: Calling the tool with the ASN reveals a plethora of information, including …
Figure 3: … the routes the packets take from the home AS to the target.
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
-
TUXEDO Computers Unveils Linux Laptop Featuring AMD Ryzen CPU
This latest release is the first laptop to include the new CPU from Ryzen and Linux preinstalled.
-
XZ Gets the All-Clear
The back door xz vulnerability has been officially reverted for Fedora 40 and versions 38 and 39 were never affected.
-
Canonical Collaborates with Qualcomm on New Venture
This new joint effort is geared toward bringing Ubuntu and Ubuntu Core to Qualcomm-powered devices.
-
Kodi 21.0 Open-Source Entertainment Hub Released
After a year of development, the award-winning Kodi cross-platform, media center software is now available with many new additions and improvements.
-
Linux Usage Increases in Two Key Areas
If market share is your thing, you'll be happy to know that Linux is on the rise in two areas that, if they keep climbing, could have serious meaning for Linux's future.
-
Vulnerability Discovered in xz Libraries
An urgent alert for Fedora 40 has been posted and users should pay attention.
-
Canonical Bumps LTS Support to 12 years
If you're worried that your Ubuntu LTS release won't be supported long enough to last, Canonical has a surprise for you in the form of 12 years of security coverage.
-
Fedora 40 Beta Released Soon
With the official release of Fedora 40 coming in April, it's almost time to download the beta and see what's new.
-
New Pentesting Distribution to Compete with Kali Linux
SnoopGod is now available for your testing needs
-
Juno Computers Launches Another Linux Laptop
If you're looking for a powerhouse laptop that runs Ubuntu, the Juno Computers Neptune 17 v6 should be on your radar.