How to find IP address conflicts in Linux

Guide

You all know what an IP address is, right? They are assigned to devices on the network to represent them. They are assigned through a DHCP server and are often changed. There are now two types of IP addresses. A dynamic one is often changed (a few days), and Static, as its name implies, is static, meaning that they do not change.

Sometimes this can cause some conflicts. When a dynamic IP is assigned and has another network device already possessed the same IP. Or, there are multiple DHCP servers that allocate IP on the same network subnet. If you have connectivity problems and assume it's due to IP collisions, you can use a tool called Arp-scan to scan them.

This tool sends an ARP (address Resolution Protocol) packet to collect addresses on the local network. If there are multiple MAC addresses claiming to have the same IP address, there is a conflict here. To install Arp-scan on Ubuntu or Debian, enter:

$ sudo apt-get install Arp-scan

For Fedora,centos or Redhat:

$ sudo yum install Arp-scan

To detect an IP conflict, run the following command:

$ sudo arp-scan–i eth0-l

Output Example:

192.168.1.10   00:1b:a9:63:a2:4c       BROTHER INDUSTRIES, ltd.192.168.1.30   00:1e:8f:58:ec:49       CANON inc.192.168.1.33   00:25:4b:1b:10:20       Apple, Inc192.168.1.37   10:9a:dd:55:d7:95       Apple Inc192.168.1.38   20:c9:d0:27:8d:56       (Unknown) 192.168.1.39   d4:85:64:4d:35:be       Hewlett Packard192.168.1.39   00:0b:46:e4:8e:6d       Cisco (dup:2) 192.168.1.40   90:2b:34:18:59:c0       (Unknown)

192.168.1.39 This IP conflict, because it appeared two times.

This article was reproduced from: http://www.linuxprobe.com/linux-found-ip-conflict/

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How to find IP address conflicts in Linux