Cisco Catalyst 2960 Series, Configuration Manual

Page: 2195 / 2288

• If the VTP mode is transparent in the startup configuration, and the VLAN database and the VTP domain
name from the VLAN database matches that in the startup configuration file, the VLAN database is
ignored (cleared), and the VTP and VLAN configurations in the startup configuration file are used. The
VLAN database revision number remains unchanged in the VLAN database.
• If the VTP mode or domain name in the startup configuration does not match the VLAN database, the
domain name and VTP mode and configuration for the VLAN IDs 1 to 1005 use the VLAN database
information.
• In VTP versions 1 and 2, if VTP mode is server, the domain name and VLAN configuration for VLAN
IDs 1 to 1005 use the VLAN database information. VTP version 3 also supports VLANs 1006 to 4094.
• From image 15.0(02)SE6, on vtp transparent and off modes, vlans get created from startup-config even
if they are not applied to the interface.
Normal-Range VLAN Configuration Guidelines
Normal-range VLANs are VLANs with IDs from 1 to 1005.
VTP 1 and 2 only support normal-range VLANs.
Follow these guidelines when creating and modifying normal-range VLANs in your network:
• Normal-range VLANs are identified with a number between 1 and 1001. VLAN numbers 1002 through
1005 are reserved for Token Ring and FDDI VLANs.
• VLAN configurations for VLANs 1 to 1005 are always saved in the VLAN database. If the VTP mode
is transparent, VTP and VLAN configurations are also saved in the switch running configuration file.
• If the switch is in VTP server or VTP transparent mode, you can add, modify or remove configurations
for VLANs 2 to 1001 in the VLAN database. (VLAN IDs 1 and 1002 to 1005 are automatically created
and cannot be removed.)
• With VTP versions 1 and 2, the switch supports VLAN IDs 1006 through 4094 only in VTP transparent
mode (VTP disabled). These are extended-range VLANs and configuration options are limited.
Extended-range VLANs created in VTP transparent mode are not saved in the VLAN database and are
not propagated. VTP version 3 supports extended range VLAN (VLANs 1006 to 4094) database
propagation in VTP server mode. If extended VLANs are configured, you cannot convert from VTP
version 3 to version 1 or 2.
• Before you can create a VLAN, the switch must be in VTP server mode or VTP transparent mode. If
the switch is a VTP server, you must define a VTP domain or VTP will not function.
• The switch does not support Token Ring or FDDI media. The switch does not forward FDDI, FDDI-Net,
TrCRF, or TrBRF traffic, but it does propagate the VLAN configuration through VTP.
• The switch supports 128 spanning tree instances. If a switch has more active VLANs than supported
spanning-tree instances, spanning tree can be enabled on 128 VLANs and is disabled on the remaining
VLANs. If you have already used all available spanning-tree instances on a switch, adding another
VLAN anywhere in the VTP domain creates a VLAN on that switch that is not running spanning-tree.
If you have the default allowed list on the trunk ports of that switch (which is to allow all VLANs), the
new VLAN is carried on all trunk ports. Depending on the topology of the network, this could create a
loop in the new VLAN that would not be broken, particularly if there are several adjacent switches that
all have run out of spanning-tree instances. You can prevent this possibility by setting allowed lists on
the trunk ports of switches that have used up their allocation of spanning-tree instances.
Consolidated Platform Configuration Guide, Cisco IOS Release 15.2(4)E (Catalyst 2960-X Switches)
2113
Information About VLANs