Toni269,
it's not an absolute requirement per se, it only depends on the vm connectivity scheme. you see, if there's a straight cross-over cable between clan and vm box you can't use clan for any other purpose since there is no connectivity to LAN. if both are connected to LAN switch and clan address is pingable on LAN you can point the phone to it and it should work. of course, provided that you have set all the stuff up, you have medpro and all that. in short, you can share clan between vm (intuity i guess?) and ip phones up to a point, i wouldn't recommend registering more than 200 phones on that clan if vm is moderately busy and if it's heavily loaded it would be good to limit ip phones to 50-100 and after that add another clan.