1. Packet Tracer 6 Building a VoIP Network (Part 3)
Eric Kwok
CCIE #43698 (R&S)
Technical Manager, APAC Region

2. Session 3 Why do we need Voice VLAN? Access port or trunk port?
Tagged or not tagged?

3. Why? Performance (Broadcast domain)
Manageability (apply policy, QoS, logical group, addressing)
Independent of Physical Topology (connect phone to any vlan access port)
Security (boundary between data and voice packet)
Access vlan 10
Voice vlan 20
Access vlan 20
(voice)
Access vlan 10
(data)

4. Phone boot up
CDP
Native VLAN 10
Voice VLAN 20
PoE Power

5. Special 802.1Q trunk through CDP
Voice VLAN
SW(config-if)# switchport mod access
SW(config-if)# switchport access vlan 10
SW(config-if)# switchport voice vlan 20
PCP (Priority or CoS)
Special 802.1Q trunk through CDP D V 20 D PC SW
Fa0/1
Data vlan 10
Voice vlan 20

6. SW#sh int switchport
Name: Fa0/1
Switchport: Enabled
Administrative Mode: static access
Operational Mode: static access
Administrative Trunking Encapsulation: dot1q
Operational Trunking Encapsulation: native
Negotiation of Trunking: Off
Access Mode VLAN: 10 (data)
Trunking Native Mode VLAN: 1 (default)
Voice VLAN: 20
Administrative private-vlan host-association: none
Administrative private-vlan mapping: none
Administrative private-vlan trunk native VLAN: none
Administrative private-vlan trunk encapsulation: dot1q
Administrative private-vlan trunk normal VLANs: none
Administrative private-vlan trunk private VLANs: none
Operational private-vlan: none
Trunking VLANs Enabled: All
Pruning VLANs Enabled:
Capture Mode Disabled
Capture VLANs Allowed: ALL
Protected: false
Unknown unicast blocked: disabled
Unknown multicast blocked: disabled
Appliance trust: none
SW#sh int switchport
Name: Fa0/6
Switchport: Enabled
Administrative Mode: dynamic auto
Operational Mode: down
Administrative Trunking Encapsulation: dot1q
Operational Trunking Encapsulation: native
Negotiation of Trunking: On
Access Mode VLAN: 1 (default)
Trunking Native Mode VLAN: 1 (default)
Voice VLAN: none
Administrative private-vlan host-association: none
Administrative private-vlan mapping: none
Administrative private-vlan trunk native VLAN: none
Administrative private-vlan trunk encapsulation: dot1q
Administrative private-vlan trunk normal VLANs: none
Administrative private-vlan trunk private VLANs: none
Operational private-vlan: none
Trunking VLANs Enabled: All
Pruning VLANs Enabled:
Capture Mode Disabled
Capture VLANs Allowed: ALL
Protected: false
Unknown unicast blocked: disabled
Unknown multicast blocked: disabled

7. CoS Ethernet Frame to include QoS
No field to specific the priority of the frame
802.1p task group to work on the traffic classes
Used in 802.1Q tag (3 bits PCP)

8. CoS in Voice Frame TPCI PCP DEI CFI VLAN ID 0x8100 Priority 0-7 VLAN
S.MAC
D.MAC
Type/
Length
Payload
FCS
S.MAC
D.MAC
802.1Q Tag
Type/
Length
Payload
FCS
TPCI
PCP
DEI
CFI
VLAN ID
0x8100
Priority
0-7
VLAN
0-4095

9. Packet capture
Lab Setup
SPAN Port
Cisco 891W
4 Ports PoE
PoE Ports

10. Phone CDP Phone sending out CDP Cisco 7970 Request 10.25W PoE power
Packet capture
Phone CDP
Phone sending out CDP
Cisco 7970
Request 10.25W PoE power
Max Power Consumption

11. Router (integrated Switch) CDP
CDP from Router
Cisco 891 Router
Native VLAN for Data (untagged)
Voice VLAN (tagged)
Available PoE Power

12. Voice VLAN 20

13. Priority in VLAN Tag (Voice and Data Frame)
Packet capture
Voice Frame VLAN 20
RTP , Pri 5
SKINNY, Pri 0, 3
7961 Data Frame untagged
Native VLAN

14. 7961 Data Frame untagged
Native VLAN
Data Frame VLAN 10, Pri 0
7970 Data Frame tagged
VLAN 10, Pri 0

15. Let‘s go to Packet Tracer
PCP (Priority or CoS) V 20 D V 20 D 20 V 10 D D
Special 802.1Q trunk through CDP

16. Session 3 Summary Why do we need Voice VLAN?
Both data vlan and voice vlan in single port
Security (diff vlan, policy) and performance (broadcast domain)
Access port or trunk port?
Special trunk or access port which can handle 802.1Q tag
Tagged or not tagged?
Voice is tagged with CoS set
Data could be tagged or not tagged depends on the phone model
Notes:
Port security, max 2 addresses