Cisco 7604 User Manual

14-2
Cisco 7600 Series Router Cisco IOS Software Configuration Guide, Release 12.2SX
OL-4266-08
Chapter 14 Configuring VLANs
Understanding How VLANs Work
VLAN Overview
A VLAN is a group of end stations with a common set of requirements, independent of physical location.
VLANs have the same attributes as a physical LAN but allow you to group end stations even if they are
not located physically on the same LAN segment.
VLANs are usually associated with IP subnetworks. For example, all the end stations in a particular IP
subnet belong to the same VLAN. Traffic between VLANs must be routed. LAN port VLAN
membership is assigned manually on an port-by-port basis.
VLAN Ranges
Note You must enable the extended system ID to use 4096 VLANs (see the “Understanding the Bridge ID”
section on page 20-2).
Cisco 7600 series routers support 4096 VLANs in accordance with the IEEE 802.1Q standard. These
VLANs are organized into several ranges; you use each range slightly differently. Some of these VLANs
are propagated to other switches in the network when you use the VLAN Trunking Protocol (VTP). The
extended-range VLANs are not propagated, so you must configure extended-range VLANs manually on
each network device.
Table 14-1 describes the VLAN ranges.
The following information applies to VLAN ranges:
• Layer 3 LAN ports, WAN interfaces and subinterfaces, and some software features use internal
VLANs in the extended range. You cannot use an extended range VLAN that has been allocated for
internal use.
• To display the VLANs used internally, enter the show vlan internal usage command. With earlier
releases, enter the show vlan internal usage and show cwan vlans commands.
• You can configure ascending internal VLAN allocation (from 1006 and up) or descending internal
VLAN allocation (from 4094 and down).
• You must enable the extended system ID to use extended range VLANs (see the “Understanding the
Bridge ID” section on page 20-2).
Table 14-1 VLAN Ranges
VLANs Range Usage
Propagated
by VTP
0, 4095 Reserved For system use only. You cannot see or use these VLANs. —
1 Normal Cisco default. You can use this VLAN but you cannot delete it. Yes
2–1001 Normal For Ethernet VLANs; you can create, use, and delete these
VLANs.
Yes
1002–1005 Normal Cisco defaults for FDDI and Token Ring. You cannot delete
VLANs 1002–1005.
Yes
1006–4094 Extended For Ethernet VLANs only. No

Cisco 7604 Specifications

General

Brand	Cisco
Model	7604
Category	Network Router
Language	English