[arch-general] manually configure network

I've just changed ISP and I can't get the changed configuration to stick. I'm using 'static IP address - manual assignment' from Network configuration wiki page. I need to change my address from 192.168.1.0/24 to 192.168.20.1/24. using iproute2 tools as per wiki I can get everything working UNTIL I reboot, at which time some of the settings show the old values and others the new. I've been manually configuring these settings without problems since I started using linux in 1994.