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VLAN numbering

Jump to: Scheme details, VLANs 1-999, VLANs 1000-4094

VLANs using IEEE 802.1Q are given tags/IDs between 1 and 4094.  These tags can be used on links between the Cambridge University Data Network (CUDN - the University backbone network) and institutional networks and must match at both ends.

Care must be taken by network administrators to ensure that the IDs used for purely internal networks within their institutions (or the CUDN itself), that do not need to pass across these links, do not clash with numbers which may be used for VLANs between networks (in particular, the CUDN and an institution).

Whilst the distinction is only important if an institutional network is importing or exporting a VLAN, institutions should bear in mind that even if they have no intention of importing or exporting VLANs now, that may change in future.  Institutions are therefore recommended to allocate VLAN numbers based on the scheme to avoid future renumbering problems.

Scheme details

Ranges of numbers are allocated for different purposes:

Reserved Reserved at the present time and must not be used.
Global Allocated by UIS Networks for global use across the CUDN; institutions must not allocate these numbers to their own VLANs.
Local Allocated for use within and by an institution without danger of clashing with numbers used by VLANs used globally across the CUDN.

The tables below show which numbers are allocated to each of these categories.

VLANs 1-999

For tags in the form x \ yz (1-999), a fairly complex scheme is used:

x \ yzx00x01x02-x09x10-x79x80-x89x90-x99
0yz - Local Local Local Local Local
1yz Local Local Local Global Global Local
2yz Reserved Reserved Global Global Global Local
3yz Reserved Reserved Global Global Global Local
4yz Reserved Reserved Global Global Global Local
5yz Reserved Reserved Global Global Global Local
6yz Reserved Reserved Global Global Global Local
7yz Reserved Reserved Global Global Global Local
8yz Reserved Reserved Global Global Global Local
9yz Reserved Reserved Global Global Global Local

The above scheme was modified during July-September 2016 with three main changes:

  • {2-9}0{2-9} (i.e. 202-209, 302-309, etc.) - from Reserved to Global status
  • {1-9}8{0-9} (i.e. 180-189, 280-289, etc.) - from Reserved to Global status
  • 2-99 - from Global to Local status

VLANs 1000-4094

For VLAN numbers of 1000 and above, a much simpler scheme is in use:

1000-1999 Local
2000-3999 Global
4000-4094 Local

Last updated: 29 September 2016

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