When it comes to configuring a separate VLAN for voice traffic, the process of configuration and VLAN creation is exactly the same whether traffic is going router-to-switch or switch-to-switch. The voice VLAN configuration differs when you want to use Cisco IP phones that incorporate a data port on the phone for PC connections. Many Cisco mid - and high - range phones such as the 7945G give users the ability to plug a PC into an Ethernet port on the phone to provide network connectivity. The phone essentially becomes a three-port switch at that point. One port connects the phone to the access-layer switch, the second (virtual) port is for voice traffic to the phone, and the third port is to connect to a PC for standard data transport. Figure below shows how a PC is plugged directly into the phone, which is essentially trunked with both a voice and data VLAN.
As you can see, the connection between the switch and the Cisco phone is an 802.1Q trunk link. It is necessary to have a VLAN trunk because we have our voice and data separated on two different VLANs. When configuring the VLAN trunk on the switchport that connects to the phone, we use a slightly different method. The Cisco IOS has a unique command to identify a VLAN as a voice VLAN. The command is switchport voice vlan. Even though the switchport command doesn’t specifically reference 802.1a, in all actuality, this trunk link between our switch and the Cisco phone is not a full-pledged 802.1Q trunk. Instead, the Cisco switch and Cisco IP phone use CDP to implement this quasi-trunk. The VLAN that is configured the voice VLAN is marked with an 802.1Q tag, while the data VLAN is considered to be the native VLAN and is left unmarked. This VLAN trunk is capable of handling only two VLANs — one tagged VLAN for voice and one untagged VLAN for data.
Configuring Voice VLAN:
Switch#configure terminal
Switch(config)#vlan 100
Switch(config-vlan)#name Voice
Switch(config-vlan)#end
Configure the int fa0/5 switchport to quasi-trunk VLAN 100 for voice and VLAN 10 for data transport:
Switch#configure terminal
Switch(config)#interface fa0/5
Switch(config-if)#switchport voice vlan 100
Switch(config-if)#switchport access vlan 10
Switch(config-if)#end
As you can see, the connection between the switch and the Cisco phone is an 802.1Q trunk link. It is necessary to have a VLAN trunk because we have our voice and data separated on two different VLANs. When configuring the VLAN trunk on the switchport that connects to the phone, we use a slightly different method. The Cisco IOS has a unique command to identify a VLAN as a voice VLAN. The command is switchport voice vlan. Even though the switchport command doesn’t specifically reference 802.1a, in all actuality, this trunk link between our switch and the Cisco phone is not a full-pledged 802.1Q trunk. Instead, the Cisco switch and Cisco IP phone use CDP to implement this quasi-trunk. The VLAN that is configured the voice VLAN is marked with an 802.1Q tag, while the data VLAN is considered to be the native VLAN and is left unmarked. This VLAN trunk is capable of handling only two VLANs — one tagged VLAN for voice and one untagged VLAN for data.
Configuring Voice VLAN:
Switch#configure terminal
Switch(config)#vlan 100
Switch(config-vlan)#name Voice
Switch(config-vlan)#end
Configure the int fa0/5 switchport to quasi-trunk VLAN 100 for voice and VLAN 10 for data transport:
Switch#configure terminal
Switch(config)#interface fa0/5
Switch(config-if)#switchport voice vlan 100
Switch(config-if)#switchport access vlan 10
Switch(config-if)#end
0 comments:
Post a Comment