Hello I have an existing private network with the address range 10.0.0.0/255.255.255.0 running a single windows 2003 domain and a firewall with internet connectivity All network devices and firewall have an address within the range and are connected with 3com 4500g switches (each switch also has an IP address within the range, switches are interconnected with 10Gb backplane) I now need to set up a brand new private network with a different range of IP addresses and a Windows 2008 domain Both networks/domains will use the existing 3com 4500g switches (switch IP addresses unchanged) and both networks/domains will need to talk to one another for migrating users/data etc from the old windows 2003 domain into the new windows 2008 domain, both networks will need to share the existing internet connection I am well used to working within a single private address range and I understand that I might need to setup a trust relationship at domain controller level but I am unsure how to setup a new address range and bridge or route between the two networks to allow devices on the old network to talk to devices on the new network and visa versa Any help or suggestions as to new IP address range and how to enable two way communication would be greatly appreciated

Both networks/domains will use the existing 3com 4500g switches (switch IP addresses unchanged) and both networks/domains will need to talk to one another for migrating users/data etc from the old windows 2003 domain into the new windows 2008 domain, both networks will need to share the existing internet connection The simple solution is to use the same subnet. I'm not sure why you think you'd need a different subnet. Until you promote the new server to a DC, it can exist on the same subnet so as to have internet access in order to do updates and such.