cisco:vlans

VLANs

Commands
- show vlan internal usage
- show vlan
Overview of VLANs
- Breaks up collision domains into multiple broadcast domains
- Layer 3 switches allow VLANs to communicate with each other
- VTP version 3 updates do not pass through promiscuous trunk ports.
VLAN Configuration Guidelines and Restrictions
- Prior to creating a VLAN, the switch must be in either VTP server or VTP transparent mode
  - In order to use VTP server mode, the VTP domain name must be prior defined
- VLANs are organized into three ranges:
  - Reserved
  - Normal
  - Extended

VLANs	Range	Usage	Propagated by VTP
0, 4095	Reserved	For system use only. You cannot see or use these VLANs.	N/A
1	Normal	Cisco default. You can use this VLAN but you cannot delete it.	Yes
2-1001	Normal	Used 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. When configuring extended-range VLANs, note the following: 1. Layer 3 ports and some software features require internal VLANs. Internal VLANs are allocated from 1006 and up. You cannot use a VLAN that has been allocated for such use. To display the VLANs used internally, enter the show vlan internal usage command. 2. Switches running Catalyst product family software do not support configuration of VLANs 1006-1024. If you configure VLANs 1006-1024, ensure that the VLANs do not extend to any switches running Catalyst product family software.You must enable the extended system ID to use extended range VLANs.	No

Parameter	Default	Valid Values
VLAN ID	1	1-4094
VLAN name	VLANx, where x is a number assigned by the software.	No range
802.10 SAID	100,001	1-4,294,967,294
MTU size	1500	1500-18,190
Translational bridge 1	1002	0-1005
Translational bridge 2	1003	0-1005
VLAN state	active	active; suspend; shutdown

Configuring VLANs
- Stored in vlan.dat file
Configuring VLANs in Global Configuration Mode
- When the switch boots, if the VTP domain name and VTP mode in the startup-config and vlan.dat files don't match, the switch uses the configuration in the vlan.dat file.