To create a dummy IP to allow the use of a single Perforce license on more than one machine: Note: Use of the license file on a duplicate machine must be approved through licensing@perforce.com. On RHEL: Below MMM.NNN.OOO.PPP is the IP address on the license file. Create a file /etc/sysconfig/network-scripts/ifcfg-dummy0 with the following lines: DEVICE=dummy0 IPADDR=MMM.NNN.OOO.PPP NETMASK=255.255.255.255 BROADCAST=MMM.NNN.OOO.PPP ONBOOT=yes Then run: ifconfig dummy0 up MMM.NNN.OOO.PPP On Ubuntu: Edit /etc/network/interfaces Add auto eth0:1 iface eth0:1 inet static address MMM.NNN.OOO.PPP netmask 255.255.255.255 broadcast MMM.NNN.OOO.PPP gateway MMM.NNN.OOO.PPP (May not be needed.) Save, and then run: /etc/init.d/networking restart On Windows: Install the MS Loopback Adaptor per: http://support.microsoft.com/kb/842561 And set the IP address to the one on the license file.