I am working on a new network for a customer who has some special needs. Their bandwidth will be provided via DSL and they are going to have several appliances that need public IP addresses: the 3Com V3001 VoIP phone system, the 3Com OfficeConnect WL-537 Wireless DSL Router, and a PC which will control the building and perimeter lighting. The DSL router is an Actiontech M1000 which is a pretty basic router with one LAN port. I set it up as a Transparent Bridge with a block of IP addresses on it. Of course, I would like to set up all of the public IP address appliances with a static address. As it turns out, the router sets itself up as DHCP server which can't be turned off or modified.

Follow up:

So my plans were skewed a little when I discovered the Actiontech DSL router acts as a DHCP server. The 3Com phone system uses both layer 2 and 3 to communicate between the phones and the call processor. In order for the phones to work on layer 2 they have to be on the same network as the call processor. Since there will be a Layer 3 phone at a remote location, the call processor will also need at least one extra public address that will be assigned as needed to an internal device (phone or analog line). The one thing I haven't figured out is how I keep someone from getting a public IP address if they happen to plug into the spare ethernet port on the back of a phone. I might have to resort to some black tape covering the port.

3Com® Baseline Plus switches are "smart" voice-ready 10/100 and Gigabit switches with easy to use, web-based configuration. They are designed for small and medium-sized businesses looking for a low-cost Layer 2 switch for demanding desktop applications, high-traffic servers, network aggregation, or uplinks to the network core.

Originally I selected the 3Com Baseline Swiitch 2816 which is an unmanaged 16 port Gigabit switch. Unfortunately because of the public address DHCP issue I had to change plans and switch to the 3Com Baseline Switch 2226 Plus which offers 24 10/100 ports and two dual-purpose Gigabit ports (copper or SFP-based fiber). With this switch I am able to setup a VLAN for the public IP addresses leaving the rest for private addresses. Management of the switch is accomplished via a web interface. It has a console port but only the switch IP address or upgrades via tftp may be performed using it.

By default all of the ports belong to VLAN 1 the default VLAN. So the first step in the configuration was to create a second VLAN and labeled it Public for the ports that will be connected to public IP addresses. I assigned ports 9-12 and 22-25 to this VLAN. I then created a third VLAN and labeled it Voice. This switch is capable of QOS so I assigned ports 9-12 and 25 to the Voice VLAN as Tagged VLAN ports. Phones will be using ports 9-12 and the call processor will use port 25. I configured the phone system to operate on this VLAN. When a phone is first booted up it will search for the call processor using normal TCP packets. When the phone establishes communication with the call processor, it will be told to switch to the Tagged Voice VLAN where it will then communicate using tagged packets.