In Linux, how does one find IP address conflicts?

You all know what an IP address is, right? They are assigned to devices on the network to represent them. They are allocated through the DHCP server and change frequently. There are two types of IP addresses. The dynamic one will change frequently (once every few days), while the static one is as static as its name.

You all know what an IP address is, right? They are assigned to devices on the network to represent them. They are allocated through the DHCP server and change frequently. There are two types of IP addresses. The dynamic one will change frequently (once a few days), while static ones are static just as their names, meaning they will not change.

Sometimes this can cause some conflicts. When a dynamic IP address is assigned and another network device already has the same IP address. Alternatively, multiple DHCP servers with IP addresses allocated on the same network subnet. If you have a connectivity problem and assume it is caused by an IP conflict, you can use a tool called arp-scan to scan them.

This tool sends an ARP (Address Resolution Protocol) packet on the local network to collect addresses. If multiple MAC addresses claim to have the same IP address, there is a conflict.

To install arp-scan on Ubuntu or Debian, enter:

 
 

  
  
___FCKpd___0nbsp;sudo apt-get install arp-scan 
 
 

For Fedora, CentOS, or RedHat:

 
 

  
  
___FCKpd___1nbsp;sudo yum install arp-scan 
 
 

To detect IP conflicts, run the following command:

 
 

  
  
___FCKpd___2nbsp;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, Inc 
  
  
192.168.1.37   10:9a:dd:55:d7:95       Apple Inc 
  
  
192.168.1.38   20:c9:d0:27:8d:56       (Unknown) 
  
  
192.168.1.39   d4:85:64:4d:35:be       Hewlett Packard 
  
  
192.168.1.39   00:0b:46:e4:8e:6d       Cisco (DUP: 2) 
  
  
192.168.1.40   90:2b:34:18:59:c0       (Unknown) 
 
 

In this example, the IP address 192.168.1.39 conflicts because it appears twice.