CISCO NETWORKING ACADEMY PROGRAM
CCNA3: Switching Basics and Intermediate Routing v3.0
VLAN Trunking Protocol
Trunking
VTP
Inter-VLAN Routing
Chapter 9 – VTP
CISCO NETWORKING ACADEMY PROGRAM
CCNA3: Switching Basics and Intermediate Routing v3.0
What is VLAN Trunking?
• A physical and logical connection between two
switches
• The trunk can carry the traffic of multiple VLANs
• Mechanism must be provided to identify VLAN
membership on the trunk link
– Tagging (802.1q)
– Encapsulation (ISL)
Chapter 9 – VTP
CISCO NETWORKING ACADEMY PROGRAM
CCNA3: Switching Basics and Intermediate Routing v3.0
802.1q Frame Tagging
• VLAN identifier inserted
into layer 2 frame
Chapter 9 – VTP
CISCO NETWORKING ACADEMY PROGRAM
CCNA3: Switching Basics and Intermediate Routing v3.0
ISL Encapsulation
• Ethernet frame is encapsulated with ISL header
and modified FCS
• Results in non-standard frame size
• Not-interoperable with non-Cisco equipment
Chapter 9 – VTP
CISCO NETWORKING ACADEMY PROGRAM
CCNA3: Switching Basics and Intermediate Routing v3.0
IOS Trunk Commands
1 Configuring trunk Links
Switch(config-if)#switchport mode trunk
Switch(config-if)#switchport trunk encapsulation dot1q
OR
Switch(config-if)#switchport mode trunk
Switch(config-if)#switchport trunk encapsulation isl
2 Verifying trunk links
Switch#show trunk
Chapter 9 – VTP
CISCO NETWORKING ACADEMY PROGRAM
CCNA3: Switching Basics and Intermediate Routing v3.0
VTP Overview
• Protocol to ensure that switches under common
administrative control have consistent VLAN
configuration & reduces complexity
• VTP messages encapsulated in ISL or dot1q frames
• Switches have 3 VTP modes
– Server – add, modify, delete VLANs
– Client – process VLAN changes and forward VTP messages
– Transparent – forward VTP messages only
Chapter 9 – VTP
CISCO NETWORKING ACADEMY PROGRAM
CCNA3: Switching Basics and Intermediate Routing v3.0
Types of VTP messages
• Advertisement requests
– Request from client switches for VLAN information
• Summary Advertisements
– VTP servers issue summary advertisements every 5
minutes with revision number
– Clients which receive a summary advertisement with
higher revision number than current create
advertisement request
• Subset advertisements
– Information from server about VLAN configuration
Chapter 9 – VTP
CISCO NETWORKING ACADEMY PROGRAM
CCNA3: Switching Basics and Intermediate Routing v3.0
Inter-VLAN routing
• Each VLAN in separate
layer 3 broadcast domain
• Router needed to switch
packets between VLANs
Chapter 9 – VTP
CISCO NETWORKING ACADEMY PROGRAM
CCNA3: Switching Basics and Intermediate Routing v3.0
Using sub-interfaces
• If you have 3 VLANs but only 1
router port
• Create a trunk port on the
switch
• Connect to router port
• Configure sub-interfaces on
the router
• Does not work on 10Mbps
interfaces
Chapter 9 – VTP