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10-2
Software Configuration Guide—Release 12.2(25)SG
OL-7659-03
Chapter 10 Understanding and Configuring VLANs, VTP, and VMPS
VLANs
You can define one or many virtual bridges within a switch. Each virtual bridge you create in the switch
defines a new broadcast domain (VLAN). Traffic cannot pass directly to another VLAN (between
broadcast domains) within the switch or between two switches. To interconnect two different VLANs,
you must use routers or Layer 3 switches. See the “Overview of Layer 3 Interfaces” section on page 22-1
for information on inter-VLAN routing on Catalyst 4500 series switches.
Figure 10-1 shows an example of three VLANs that create logically defined networks.
Figure 10-1 Sample VLANs
VLANs are often associated with IP subnetworks. For example, all of the end stations in a particular IP
subnet belong to the same VLAN. Traffic between VLANs must be routed. You must assign LAN
interface VLAN membership on an interface-by-interface basis (this is known as interface-based or
static VLAN membership).
You can set the following parameters when you create a VLAN in the management domain:
• VLAN number
• VLAN name
• VLAN type
• VLAN state (active or suspended)
• Maximum transmission unit (MTU) for the VLAN
• Security Association Identifier (SAID)
• VLAN number to use when translating from one VLAN type to another
Note When the software translates from one VLAN type to another, it requires a different VLAN number for
each media type.
Floor 1
Floor 2
Engineering
VLAN
Cisco router
Fast
Ethernet
Floor 3
Marketing
VLAN
Accounting
VLAN
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