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  OIT Home > Committees > CNC-BEG > VLAN ID Number Assignments
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VLAN Identification Number Assignments



All hexidecimal numbers will begin with "0x", octal numbers begin with "0," and decimal numbers begin with a non-zero digit.

The term "registry" refers to the entity providing VID allocation and registration services.

The term "forwarding device" refers to devices that process and forward packets between ports and/or VLANs based upon frame contents at layer 2 or higher. This would include routers and switches, but not hubs or single-homed (i.e. on a single physical and logical connection) end stations.


This document specifies the mechanism for assignment and use of VLAN identifiers at UC Santa Barbara. It is assumed that VLAN Identification (VID) values will be applied according to the specifications contained in IEEE 802.1Q. The following criteria were designed based upon the 802.1Q specification.

Motivation for This Document

As VLAN usage becomes commonplace on campus, it is likely that switch infrastructures from separate organizational entities will interconnect to extend VLAN services. For example, a department may have offices in separate locations on campus, and may want to extend an internal LAN between these locations. A switched campus backbone with VLAN support could provide this connectivity, but it requires that the VLAN numbering be managed to avoid a VID conflict. Two departments utilizing the same VID would result in such a conflict.

A separate problem, not likely to be significant in the near term, is the limited number of VIDs available. While 4,093 unique IDs may be allocated, it is in the collective interests of the campus to avoid utilizing significant portions of the address range. Initial allocations of IP address space were made without conservation in mind, resulting in more stringent allocation requirements, subnet reallocations and "reposessions". Conservative initial deployments of VIDs may help to avoid a similar situation with VIDs.


There are a maximum of 4096 possible values ranging from 0 to 4095. Some of these values are reserved as shown below:

Value Meaning 0 Contains user_priority data (802.1Q) 1 Default Port VID (802.1Q) 4095 Reserved (802.1Q)

Specification: Initial Deployment

This specification is a recommended method for initial deployment of VIDs. Actual allocations must be made by the registry. It should be recognized that this allocation procedure is based upon a best estimate as to possible usage over the next two years. As such, allocations may be made following alternate formulas or ad-hoc as necessary. The objective should be to maintain consistent addressing while minimizing wasted address space.

Splitting the 12-bit VID along bit boundaries:


Where NN = Network (00 == 128.111/16, other values may not be network-dependent)
SS = Subnet (Class C, e.g. 0001 0000 == 16)
VV = Subnet VLAN IDs (00-11)

Under this scheme, each Class C subnet on 128.111 could use up to 4 VLAN IDs. These VIDs could be calculated as: ((SUBNET*4) + 4) through ((SUBNET*4) + 4 + 3). Because the numbering begins at 4, no conflicts with fixed values assigned by 802.1Q are anticipated. The two Class C networks at UCSB would be assigned values beginning with bits 010, as it would not be a good use of VIDs to assign them separate Network ID values. Values beginning with 011 may be available for use within private (i.e., departmental, not connected across common campus backbones) networks not associated with a single subnet, thus reserving the range 1536-2047. This keeps over half the VID range available for future allocation.

Whenever a range of VIDs is available, numbering should begin with the lowest possible VID. For example, 128.111.30/23 could use the reserved ranges for 128.111.30/24 or 128.111.31/24, but should start use within 128.111.30/24 ( 30*4+4 == 124 == 0000 0111 1100).

Hardware Requirements

All forwarding devices utilizing 802.1Q capabilities must be 802.1Q compliant. Forwarding devices carrying 802.1Q traffic must support and have enabled SNMPv1 or better. Switches carrying 802.1Q traffic must support and have enabled 802.1d spanning tree. The full range (1-4,095) of VLAN IDs must be supported by the 802.1Q implementation.

Registration Requests

All registration requests must be made by individuals employed by the University on at least a 50% time basis, or as accepted by a majority vote of the Backbone Engineering Group. Registration requests must be approved by the appropriate department or unit head.

Registration requests must include:

  1. Applicant's name and contact information.
  2. Department(s) requesting and utilizing the VID.
  3. Description of planned VID usage, including buildings where VID will be deployed.
  4. For each forwarding device (see definition in Conventions section above) carrying VLAN-tagged traffic:
    1. The physical location of the device, including room number.
    2. The IP address(es) used by the device.
    3. An SNMP read-only community name accessible by Campus Network Programmers and Network Operations Center staff.
    4. Upon request, a copy of any vendor-specific MIB supported by the device.

The registry will be operated by the campus hostmaster, and queries regarding registrations may be directed to hostmaster@ucsb.edu or by calling x3221. Registration requests will be processed within three business days.

No VID may be used without explicit allocation by the registry.

Registration Information Usage

Registration information supplied by departments will be made available to staff within the Campus Network Programmers and Network Operations Center organizations.

A list of allocated VIDs will be made publicly available, include a description and the responsible department's name.

Operational Responsibility

Once a VID is allocated, it is the responsibility of the requesting department to ensure the integrity of VLAN operation except for that part of a VLAN that traverses common campus data network infrastructure. The requesting department must also ensure the registration information is kept current. Any VID for which registration information is not maintained, is operated other than originally requested, or interferes with network operations, may be revoked. Notification of revocation will be provided to the requesting department's chair and/or MSO, as well as the applicant. VID usage must cease in a timely manner as defined by hostmaster, and revoked VIDs may be immediately blocked from utilizing campus network resources.

Procedure Clarification, Enhancement, and Dispute Resolution

Any issue not sufficiently defined by this statement or for which a significant dispute exists may be forwarded to the Backbone Engineering Group at the discretion of the BEG chair.

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Last modified: 10/19/2007