<SNIP> 1/ How can I know those servers are same network as those net mask is /32 if not the same network, I have problem when two servers are slowing in transferring files </SNIP> Check the subnet mask, i doubt its going to be 255.255.255.255 <SNIP> 2/ lf the network card in server has problem and need change another one, will my ip address change to another ip address also? </SNIP> Yeah well thats how dhcp works, via ma caddy, i guess you can always spoof your old mac address. <SNIP> 3/ why hosting company is using /32 and dhcp? what is advantage? ls it easy for administration? </SNIP> Im guessing because the users are to stupid to understand what a subnet mask/gateway is its just easier to get the mac address and assign it to a user then let the user assign a ip. Normally in a co-location setup its not like this, inless its very cheap hosting. My co-location has the following setup, and this is how MOST networks should be run. Core router using BGP to transit providers, and other local peers. Switched network useing ospf to handle the routes and also VLAN's for the customers subnets. So customer should get a vlan assigned to them (which they have no need to know what the number is, they are handed a access mode port. Customers also issued a /30 (at least) in most cases a customer will get a /29 or /28 depending on what they need. In this case of a /30 its a total of 3 address's 1, GATEWAY (put on the ISP/HOST switch 2, IP ADDRESS FOR SERVER TO USE 3, BROADCAST ADDRESS. Heres an eg of a /30: Address: 192.168.1.1 11000000.10101000.00000001.000000 01 Netmask: 255.255.255.252 = 30 11111111.11111111.11111111.111111 00 Wildcard: 0.0.0.3 00000000.00000000.00000000.000000 11 => Network: 192.168.1.0/30 11000000.10101000.00000001.000000 00 HostMin: 192.168.1.1 11000000.10101000.00000001.000000 01 HostMax: 192.168.1.2 11000000.10101000.00000001.000000 10 Broadcast: 192.168.1.3 11000000.10101000.00000001.000000 11 Hosts/Net: 2 Class C, Private Internet Heres an eg of a /29: the % ipcalc 192.168.1.1/29 Address: 192.168.1.1 11000000.10101000.00000001.00000 001 Netmask: 255.255.255.248 = 29 11111111.11111111.11111111.11111 000 Wildcard: 0.0.0.7 00000000.00000000.00000000.00000 111 => Network: 192.168.1.0/29 11000000.10101000.00000001.00000 000 HostMin: 192.168.1.1 11000000.10101000.00000001.00000 001 HostMax: 192.168.1.6 11000000.10101000.00000001.00000 110 Broadcast: 192.168.1.7 11000000.10101000.00000001.00000 111 Hosts/Net: 6 Class C, Private Internet Hope this makes sence. Regards, Bruce