IP Phones

Traditional phones operate over the public switched telephone network (PSTN). Sometimes this is called POTS (Plain Old Telephone Service).

IP phones use VoIP (Voice over IP) technologies to enable phone calls over an IP network, such as the Internet.

IP phones are connected to a switch just like any other end host.

IP phones have an internal 3-port switch.

• uplink to the external switch.

• downlink to the PC.

• 1 port connects internally to the phone itself.

This allows the PC and the IP phone to share a single switch port. Traffic from the PC passes through the IP phone to the switch.

It is recommended to separate 'voice' traffic (from the IP phone) and 'data' traffic (from the PC) by placing them in separate VLANs.

• This can be accomplished using a voice VLAN.

• Traffic from the PC will be untagged, but traffic from the phone will be tagged with a VLAN ID.

Configuration

SW1(config-if)# switchport voice vlan 11

PC1 will send traffic untagged as normal. SW1 will use CDP to tell PH1 to tag PH1's traffic in VLAN 11.

SW1# show interfaces g0/0 switchport
...
Administrative Mode: static access
Operational Mode: static access
...

Although the interface send/receives traffic from two VLANs, it is not considered a trunk port. It is considered an access port.