Finding Duplicate IP Addresses on the Network

  1. Install arp-scan.
  2. Run the following command:
$ sudo arp-scan -I eth0 -l | grep
$ OR
$ sudo arp-scan -I eth0 -l | grep DUP    00:c0:b7:55:f6:1f       AMERICAN POWER CONVERSION CORP (DUP: 2)   00:1b:00:0f:55:0e       Neopost Technologies (DUP: 2)   00:14:38:48:75:b7       Hewlett Packard (DUP: 2)

Capturing cupsd Traffic

First to get the list of open ports used by cupsd, use netstat:

$ sudo netstat -lntup | grep cupsd

tcp        0      0*  LISTEN      512/cupsd
tcp6       0      0 :::631             :::*       LISTEN      512/cupsd
udp        0      0*              512/cupsd

tcpdump can’t be used so need to use strace here:

$ sudo strace -p 512 -f -e trace=network -s 10000 -o capture.out &
$ sudo lpinfo -v

This will capture the HTTP messages (IPP) received by cupsd.