Vlan Configuration Files - Cisco Catalyst 2960 series Configuration Manual

Information About VLANs
Membership Mode
Trunk (IEEE 802.1Q) :
• IEEE 802.1Q—
Industry-standard trunking
encapsulation.
Dynamic access
Voice VLAN

VLAN Configuration Files

Configurations for VLAN IDs 1 to 1005 are written to the vlan.dat file (VLAN database), and you can display
them by entering the show vlan privileged EXEC command. The vlan.dat file is stored in flash memory. If
the VTP mode is transparent, they are also saved in the switch running configuration file.
In a switch stack, the whole stack uses the same vlan.dat file and running configuration. On some switches,
the vlan.dat file is stored in flash memory on the active switch.
You use the interface configuration mode to define the port membership mode and to add and remove ports
from VLANs. The results of these commands are written to the running-configuration file, and you can display
the file by entering the show running-config privileged EXEC command.
When you save VLAN and VTP information (including extended-range VLAN configuration information)
in the startup configuration file and reboot the switch, the switch configuration is selected as follows:
Consolidated Platform Configuration Guide, Cisco IOS Release 15.2(4)E (Catalyst 2960-X Switches)
2112
VLAN Membership Characteristics
A trunk port is a member of all
VLANs by default, including
extended-range VLANs, but
membership can be limited by
configuring the allowed-VLAN
list. You can also modify the
pruning-eligible list to block
flooded traffic to VLANs on trunk
ports that are included in the list.
A dynamic-access port can belong
to one VLAN (VLAN ID 1 to
4094) and is dynamically assigned
by a VLAN Member Policy Server
(VMPS).
The VMPS can be a Catalyst 6500
series switch, for example, but
never a Catalyst switch. The
Catalyst switch is a VMPS client.
You can have dynamic-access ports
and trunk ports on the same switch,
but you must connect the
dynamic-access port to an end
station or hub and not to another
switch.
A voice VLAN port is an access
port attached to a Cisco IP Phone,
configured to use one VLAN for
voice traffic and another VLAN for
data traffic from a device attached
to the phone.
VTP Characteristics
VTP is recommended but not
required. VTP maintains VLAN
configuration consistency by
managing the addition, deletion,
and renaming of VLANs on a
network-wide basis. VTP
exchanges VLAN configuration
messages with other switches over
trunk links.
VTP is required.
Configure the VMPS and the client
with the same VTP domain name.
To participate in VTP, at least one
trunk port on the switch or a switch
stack must be connected to a trunk
port of a second switch or switch
stack.
VTP is not required; it has no effect
on a voice VLAN.