Please note that owing to the University having to conserve remaining unallocated IPv4 subnet for new departments, the previously standard procedure of allocating bigger subnets is now severely restricted. Units will likely be expected to accommodate extra client hosts by using technologies such as NAT/PAT.
You should ensure that you are familiar with the University's IPv4 Address Allocation Policy.
As units expand or simply acquire more computers, they may find that their existing IP address ranges become full. As the University's unallocated IPv4 pool shrinks it has become necessary to become stricter with new allocations. The University continues to acquire and create new departments and we have to ensure that these departments are able to receive some addresses. Owing to the shortage we are no longer in a position to allocate subnets bigger than /24 in size.
In general, if a Unit wishes to apply for more address space they must meet the following conditions :
- All printers, switching infrastructure and other devices which do not need Internet access must be migrated to RFC1918
- The existing allocation must be 90% full
- Documentation showing expected future growth must be provided
If we are satisfied that a unit has exhausted the space in its existing IP address range, then we will agree to a move. This has the disadvantage of requiring a complete renumbering of all IP addresses. However it is far preferable in the long term to adding a second subnet to an existing backbone connection, not least because of the problems of internal routing between the two subnets.
In many cases the move will be from an existing 254-address range (for instance 22.214.171.124/255.255.255.0, with valid IP addresses in the range 126.96.36.199 to 188.8.131.52) to a 510-address range (for instance 184.108.40.206/255.255.254.0 with addresses in the range 220.127.116.11 to 18.104.22.168).
We are sometimes asked whether it is possible simply to extend the existing IP address range without having to renumber completely. In general this is not possible owing to the adjacent block of network numbers being in use by another college or department. Even in the cases where it is free, the migration is nontrivial as it requires a "big bang" approach in which the netmask and default gateway of all hosts on the network require changing simultaneously. This has been done, but in general is not to be recommended, especially on large and diverse networks.