Voice over IP & IP Phone

VoIP is a technology that makes voice conversations available using internet technology. VoIP can be done using IP Phones. An IP phone has 3 port one to go to the switch, another to the phone's ASIC and the other one goes to the laptop/PC. In this configuration, nothing needs to be done on the PC if it was directly connected to the switch and can send traffic.

The link between the switch and IP Phone can be configured in several ways:

1. Access Link. If this is implemented, voice traffic and data traffic will be mixed up and no priority is given to voice traffic. Frames who come first, get served first. The advantage is that there needs nothing to be done to apply this option (Default). The disadvantage is that if there are lots of data traffic, voice traffic will be disturbed by delays and this should be prevented since voice is delay sensitive.


2. Trunk link and use 802.1p. This option will tag voice traffic as high priority. It will also send traffic through its default voice native VLAN which is VLAN 0. VLAN 0 needs to be created manually, because it is sometimes not automatically created.

3. Trunk link and not tagging voice traffic (untagged). In this way, the IP phone is able to send untagged voice traffic.

4. Trunk link and specify a specific Voice VLAN. THe IP Phone will forward traffic with a specific VLAN.

To configure voice traffic in an interface put the command:
(config-if)#switchport voice vlan /dot1p/none/untagged


-- 24 November 2010 --