Private IP Numbers

Private IP networks are "organizationally scoped" IP nets which the university uses internally but are not routed outside the institution. This is consistent with the Address Allocation for Private Internets (RFC1918).

Prefix First Address Last Address Number of Addresses
10.0.0.0/8 10.0.0.0 10.255.255.255 16,777,216
172.16.0.0/12 172.16.0.0 172.31.255.255 1,048,576
192.168.0.0/16 192.168.0.0 192.168.255.255 65,536

University of Michigan Private IP Assignments

Historically, the university has scoped the organization for private IP address on the Ann Arbor campus, and this is divided between the two core network providers, ITS and HITS. Some specifics include:

  • Each group is responsible for the administration of prefixes within its assigned ranges.
  • A range of IP space designated as “shared” may be routed between core networks.
  • Ranges designated as “local” will not be routed between core networks.
  • One block of private IP space (172.31.0.0/17) is routeable betwen the ITS core network and Dearborn.
  • One block of private IP space (172.31.128.0/17) is routable between the ITS core network and Flint.
  • Two blocks (10.215.0.0/16 and 10.216.0.0/16) are routable between Dearborn and Flint.

Note: Units must request private IP address space from their campus core network provider to ensure addressing conflicts do not exist.

10.0.0.0/8 Assignments

Core Network Prefix First Address Last Address Announcement
Any 10.0.0.0/9 10.0.0.0 10.127.255.255 Not announced by any core network (See 10.0.0.0/8 Exceptions Table below)
UMHS 10.128.0.0/11 10.128.0.0 10.159.255.255 May be announced by UMHS
UMnet 10.160.0.0/11 10.160.0.0 10.191.255.255 May be announced by UMnet
Shared 10.192.0.0/11 10.192.0.0 10.223.255.255 Announcements by mutual agreement (See 10.0.0.0/8 Prefixes Announced by Mutual Agreement Table below)
UMnet 10.224.0.0/11 10.224.0.0 10.255.255.255 May be announced by UMnet
(See 10.0.0.0/8 Exceptions Table below)

10.0.0.0/8 Exceptions

Prefix Announced by Comments
10.75.144.0/20 UMnet Mirror of 207.75.144.0/20
10.108.8.0/21 UMnet Mirror of 198.108.8.0/21
10.111.0.0/16 UMnet Engineering Lab Mirror of 198.111.0.0/16
10.255.0.0/16 Not Routed

LAN-Local (Cannot provide DNS or DHCP services to LAN-Local addresses.)

10.0.0.0/8 Prefixes Announced by Mutual Agreement

Prefix Announced by Comments
10.194.0.0/16 UMnet Mirror of 67.194.0.0/16
10.200.0.0/22 UMnet Bioinformatics
10.211.0.0/16 UMnet Mirror of 141.211.0.0/16
10.212.0.0/16 UMnet Mirror of 141.212.0.0/16
10.213.0.0/16 UMnet Mirror of 141.213.0.0/17
10.214.0.0/16 UMHS Mirror of 141.214.0.0/16
10.215.0.0/16 Dearborn Mirror of 141.215.0.0/16
10.216.0.0/16 Flint Mirror of 141.216.0.0/16

Note: The mirrored IP prefixes above are reserved for use on the networks where mirrored public prefixes are used. Units needing private IP space can generally assume that these prefixes will be available for intra-campus use. Contact umnet-administration@umich.edu to activate these private prefixes.

172.16.0.0/12 Assignments

Backbone Prefix First Address Last Address Announcement Comments
UMHS 172.16.0.0/16 172.16.0.0 172.16.255.255 May be announced by UMHS  
UMHS 172.17.0.0/16 172.17.0.0 172.17.255.255 May be announced by UMHS  
None 172.18.0.0/16 172.18.0.0 172.18.255.255 Not announced Reserved for future use
None 172.19.0.0/16 172.19.0.0 172.19.255.255 Not announced Reserved for future use
Any 172.20.0.0/16 172.20.0.0 172.20.255.255 Not announced  
UMnet 172.21.0.0/16 172.21.0.0 172.21.255.255 May be announced by UMnet  
Any 172.22.0.0/16 172.22.0.0 172.22.255.255 Not announced  
UMnet 172.23.0.0/16 172.23.0.0 172.23.255.255 May be announced by UMnet  
Any 172.24.0.0/16 172.24.0.0 172.24.255.255 Not announced  
Any 172.25.0.0/16 172.25.0.0 172.25.255.255 Not announced  
Any 172.26.0.0/16 172.26.0.0 172.26.255.255 Not announced  
None 172.27.0.0/16 172.27.0.0 172.27.255.255 Not announced Reserved for future use
UMnet 172.28.0.0/16 172.28.0.0 172.28.255.255 May be announced by UMnet VoIP
UMnet 172.29.0.0/16 172.29.0.0 172.29.255.255 May be announced by UMnet VoIP
UMHS 172.30.0.0/16 172.30.0.0 172.30.255.255 May be announced by UMHS VoIP
Dearborn 172.31.0.0/17 172.31.0.0 172.31.127.255 May be announced by Dearborn VoIP
Flint 172.31.128.0/17 172.31.128.0 172.31.255.255 May be announced by Flint VoIP

192.168.0.0/16 Assignments

Core Network Prefix First Address Last Address Announcement
Shared 192.168.0.0/18 192.168.0.0 192.168.63.255 Announcements by mutual agreement (See 192.168.0.0/16 Prefixes Announced by Mutual Agreement Table below)
Any 192.168.64.0/18 192.168.64.0 192.168.127.255 Not announced
Any 192.168.128.0/17 192.168.128.0 192.168.255.255 Not announced
(Reserved for LAN-local use - may be used freely on any LAN and will never be routed across the UMnet Core Network. Cannot provide DNS or DHCP services to LAN-Local addresses.)

192.168.0.0/16 Prefixes Announced by Mutual Agreement

Prefix Announced by Comments
192.168.50.0/24 UMnet Turbo Research Storage