RFC1918 describes a set of network ranges set aside for so-called "private" use. This document provides important information for IT Officers who may be considering using these addresses on their network.
Hostmaster at IT Services follows a policy of always providing public IP addresses to units as outlined on the IPv4 Address Allocation Policy page. The University was in a fortunate position in having considerable public IP space, but the remainder must now be carefully managed. For example devices which have no need to contact the Internet or be accessible to other systems in Oxford, such as printers and network switches, may be allocated RFC1918 addresses.
Where there is no requirement to use your public IP addresses allocated by Hostmaster at IT Services, you may be able to make use of these networks. For example, some devices which do not (and should not) need Internet access, such as IP CCTV cameras, may be good candidates for moving onto RFC1918.
The RFC1918 ranges are:
- 10.0.0.0 - 10.255.255.255 (10/8 prefix)
- 172.16.0.0 - 172.31.255.255 (172.16/12 prefix)
- 192.168.0.0 - 192.168.255.255 (192.168/16 prefix)
Some of these address ranges are reserved for specific use within the University (see "RFC1918 usage guidance notes" below).
The available RFC1918 subnets for use within the college/Departament internal networks are listed on the IPv4 Address Allocation Policy page. This will eventually allow us to allocate and hence route some RFC1918 addresses within the Odin network, giving greater scope for (re-)using the remaining limited public IP address space.
RFC1918 usage guidance notes
While Units can technically use any RFC1918 networks they like within their own local network scope (after all this is how RFC1918 was designated), they may find it helpful to avoid certain ranges in order to avoid certain side-effects.
- 10.128.0.0/9 - will not be used in the University's backbone global routing table nor be assigned records in the DNS. Can be freely used.
- 10.0.0.0/9 - may be used in the University's backbone global routing table or be assigned records in the DNS - to be avoided, as per the IPv4 Address Allocation Policy
For example, 10.112.0.0/12 is assigned to the Campus RFC1918 service which is routed around the backbone and has DNS assignments.
172.16.0.0/12 (to be avoided - as per the IPv4 Address Allocation Policy)
This netblock is used by central networking infrastructure and may feature in the DNS.
192.168.0.0/16 (can be freely used)
This netblock is not used by central networking infrastructure in any capacity.