If you are using dhcp, you should not have to do much. If the machine is off, turning it on will get an IP on the right subnet. If it is on, you will need to dhcpmon -t to kill the dhcp client, then ifconfig lan0 down - ifconfig lan0 delete then the dhcpstrt -i lan0 -d 0 that Remy referenced (or reboot instead of all that) If you are using a static IP, you can use tcpcfg2 as Remy stated, or edit the \mptn\bin\setup.cmd directly that Remy referenced (fixing the ifconfig and route statements). You'll then need to ifconfig lan0 down ifconfig lan0 delete and run setup.cmd (or reboot instead of all that after editing the setup.cmd).
It is easier than I make it sound there, but I don't know whether you are using dhcp or static.