During the course of this afternoon we will be changing our IPv6 allocation policy. This change should have minimal impact, and will go unnoticed by most users.

Our original IPv6 address allocation policy provided for one subnet per IPv4 network, assigned based on the decimal value of the VLAN ID. So in Struben building, being VLAN 88, the IPv6 subnet was 2001:4200:1010:1088::/64. This has worked well for a number of years.

Unfortunately we're now using VLAN IDs on campus that are larger than 1000, and so don't fit into the current allocation policy. For this reason we're changing the allocation policy to represent the VLAN ID in hexadecimal rather than decimal. Thus, for the example above, the new IPv6 subnet will be 2001:4200:1010:1058::/64. This new allocation policy, whilst more difficult to calculate, will allow us to use the full range of VLAN ID space without further changes.

Anyone using IPv6 and obtaining an address via router solicitation will automatically gain a new address in the correct range (this includes most Linux boxes, Windows Vista, and Apple Macs). People who've created static entries for IPv6 addresses will need to change them manually.

The IPv6 addresses of core IT services are not changing.