Network Design Question

[prontospyder]

I'm designing a small business network for a class project. One of the requirements is to have an addressing scheme (subnetting).
Here's the configuration:

There's 7 clients hooked up to an 8 port hub.
The server/hub/dsl modem/wireless access point is hooked up to a Secure Gateway.
There's 1 client hooked up to the wireless access point.

Is it OK to have just one subnet (IP Address range of 192.168.0.2-192.168.0.10 with subnet mask of 255.255.255.0) or do I have to create 3 subnets for this small network?

Thanks.

 

[Lord Evermore]

I'm not clear on exactly how you have the setup. Lay out the path from the DSL line inward, like: DSL line to DSL modem, to Secure Gateway (and explain what that is for the idiots like me), then the WAP, server and hub connected to the secure gateway (do they connect to a switch connected to the gateway, or a hub, or are they each connected on separate NICs in the gateway?). Whatever the layout is. I can't tell from your post, because of the inclusion of the DSL modem with all the other devices.

The address range you specified isn't a subnet, it's just a range of IPs from the Class C reserved network of 192.168.0.0/24. A subnet by definition is a segment of the full classful network space, the subnet mask wouldn't be anything .0 unless you were subnetting a class B or A network.

The range you'd need to use in order to have 8 internal computers plus the gateway address would have to be a 16 address subnet. So it would be 192.168.0.0/28 (subnet mask 255.255.255.240). The network address is .0, the address assigned to the gateway that all the computers pass through (presumably the secure gateway) would be .1, and then the range from 2 through 14 is available for clients. (For extra points, you could specify that the gateway address be .14, because this provides a tiny tiny bit of extra security, though it's not entirely useful on an internal network.)

 

[prontospyder]

Here's the secure gateway:

3Com Officeconnect Cable/DSL Secure Gateway

 

[prontospyder]

Originally posted by: Lord Evermore
I'm not clear on exactly how you have the setup. Lay out the path from the DSL line inward, like: DSL line to DSL modem, to Secure Gateway (and explain what that is for the idiots like me), then the WAP, server and hub connected to the secure gateway (do they connect to a switch connected to the gateway, or a hub, or are they each connected on separate NICs in the gateway?). Whatever the layout is. I can't tell from your post, because of the inclusion of the DSL modem with all the other devices.

The address range you specified isn't a subnet, it's just a range of IPs from the Class C reserved network of 192.168.0.0/24. A subnet by definition is a segment of the full classful network space, the subnet mask wouldn't be anything .0 unless you were subnetting a class B or A network.

The range you'd need to use in order to have 8 internal computers plus the gateway address would have to be a 16 address subnet. So it would be 192.168.0.0/28 (subnet mask 255.255.255.240). The network address is .0, the address assigned to the gateway that all the computers pass through (presumably the secure gateway) would be .1, and then the range from 2 through 14 is available for clients. (For extra points, you could specify that the gateway address be .14, because this provides a tiny tiny bit of extra security, though it's not entirely useful on an internal network.)

Thanks for clearing up the subnet issue. I've done a lot of practice problems on it and still is having trouble remembering it.

 

[Lord Evermore]

After you do it a lot, it becomes second nature, you just automatically remember what subnet goes to which CIDR notation and what subnet size. Easy to get out of practice though if you don't use it for awhile, and if you only use it for a couple of classes it doesn't get drilled in as well.

Okay, so the secure gateway is just a cable/dsl router like any other, with firewall functions. Priced the way other 3Com devices are even though 20 other companies make the same thing that cost a third as much.

I assume that the hub connects to one of the LAN ports, a server connects to another port, and the WAP connects to a third port. The DSL modem connects to the WAN port.

Because of this setup, yes you can use a single subnet. You have to look at the 4 ports on the gateway as being an "internal switch" rather than 4 separate network ports. If you drew out the path that data flows, it would be as if the gateway only had the external WAN port, and one internal Ethernet port, connected to a 5-port switch, which happens to be inside the same casing. The "5th" port is the one that connects the internal switch to the LAN interface of the gateway, and the other 4 ports are available for your LAN. When you assign an IP address and subnet to the gateway's LAN interface, that is the subnet that is used for all devices connected to the LAN ports. Since all your connections are going through simple hubs and switches (the WAP is just a bridge, but you may need to access a configuration for it to make sure it's set to only do that), so they all act as one network.

If instead of that gateway you used a computer firewall, with one NIC for the DSL modem, one NIC for the hub, one NIC for the server and one NIC for the WAP, then each of the 3 LAN NICs would have to be using a different subnet, because they are different physical networks.