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:
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).
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.
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
Registration requests must include:
- Applicant's name and contact information.
- Department(s) requesting and utilizing the VID.
- Description of planned VID usage, including buildings where
VID will be deployed.
- For each forwarding device (see definition in Conventions
section above) carrying VLAN-tagged traffic:
- The physical location of the device, including room number.
- The IP address(es) used by the device.
- An SNMP read-only community name accessible by Campus
Network Programmers and Network Operations Center staff.
- 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 firstname.lastname@example.org 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.
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
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.