Cisco Systems 8540 Manual De Usuario
4-10
Layer 3 Switching Software Feature and Configuration Guide
78-6235-04, Cisco IOS Release 12.0(10)W5(18)
Chapter 4 Configuring Interfaces
Configuring 802.1Q VLAN Encapsulation
Example
The following example shows how to configure the interfaces for VLAN bridging with ISL
encapsulation shown in Figure 4-2:
encapsulation shown in Figure 4-2:
Router(config)# interface fastethernet 1/0/1.1
Router(config-subif)# encap isl 50
Router(config-subif)# bridge-group 1
Router(config-subif)# interface fastethernet 1/0/0
Router(config-if)# bridge-group 1
Router(config-if)# exit
Router(config)# bridge 1 protocol ieee
Router(config)# interface fastethernet 1/0/1.2
Router(config-subif)# encap isl 100
Router(config-subif)# bridge-group 2
Router(config-subif)# interface fastethernet 3/0/1
Router(config-subif)# bridge-group 2
Router(config-subif)# exit
Router(config)# bridge 2 protocol ieee
Router(config)# exit
Router# copy system:running-config nvram:startup-config
When configuring ISL with IP, you cannot configure IP addresses on a subinterface unless the VLANs
are already configured (that is, you must have already entered the encapsulation isl or encapsulation
dot1q command). That is not the case with IPX, however—you can configure IPX networks on a
subinterface even when the VLANs have not been configured.
are already configured (that is, you must have already entered the encapsulation isl or encapsulation
dot1q command). That is not the case with IPX, however—you can configure IPX networks on a
subinterface even when the VLANs have not been configured.
The maximum VLAN bridge group values are as follows:
•
Maximum number of bridge groups: 64
•
Maximum number of interfaces per bridge group: 128
•
Maximum number of subinterfaces per system: 255
For a complete configuration example for VLANs with ISL encapsulation, see the “Catalyst 8540 CSRwith ISL, VLAN, and BVI with GEC” section on page C-1.
To monitor the VLANs once they are configured, use the commands described in the “Monitoring
VLAN Operation” section on page 4-12.
VLAN Operation” section on page 4-12.
Configuring 802.1Q VLAN Encapsulation
The IEEE 802.1Q standard provides a method for secure bridging of data across a shared backbone.
IEEE 802.1Q VLAN encapsulation uses an internal, or one level, packet tagging scheme to multiplex
VLANs across a single physical link, while maintaining strict adherence to the individual VLAN
domains.
IEEE 802.1Q VLAN encapsulation uses an internal, or one level, packet tagging scheme to multiplex
VLANs across a single physical link, while maintaining strict adherence to the individual VLAN
domains.
On an IEEE 802.1Q trunk port, all transmitted and received frames are tagged except for those on the
one VLAN configured as the PVID (port VLAN identifier) or native VLAN for the port. Frames on the
native VLAN are always transmitted untagged and are normally received untagged.
one VLAN configured as the PVID (port VLAN identifier) or native VLAN for the port. Frames on the
native VLAN are always transmitted untagged and are normally received untagged.
The VLAN configuration example shown in Figure 4-3 depicts the following:
•
Fast Ethernet ports 1/0/0 and subinterface 1/0/1.1 on the switch router are in bridge group 1. They
are part of native VLAN 1, which uses 802.1Q encapsulation.
are part of native VLAN 1, which uses 802.1Q encapsulation.
•
Fast Ethernet port 3/0/1 and subinterface 1/0/1.2 are in bridge group 2. They are part of VLAN 100,
which uses 802.1Q encapsulation.
which uses 802.1Q encapsulation.
•
Fast Ethernet port 1/0/1 is configured as an 802.1Q trunk.