A configuration that may help was already commented below, but to expound on it the following may be helpful.

Cisco switches allow you to have multiple vlans, the configuration of it would look like the following if you did a show running command:

Interface FastEthernet0/1

switchport access vlan 260

switchport mode access

The vlan number is unimportant in the discussion because you can set it to any value you wish, except for vlan 1 which is the "default" vlan in the configuration. All devices will be able to talk at the layer 2 level if you use the default vlan, but if you are trying to have different layer 3 subnets talk to each other on top of having cobranet devices connected to those different layer 3 subnets, you'll want to use multiple vlans.

A vlan creates a broadcast domain among different devices. All devices you assign to the same vlan will be able to talk at the layer 2 level, and any devices you assign an ip address in the same subnet will be able to talk to those devices as well.

Do you have a test setup or perhaps an idea of how the final network will be setup? Will there be servers on different subnets?