Private IP Numbers

Private IP networks are "organizationally scoped" IP nets which the University of Michigan 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 routable between 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)
Michigan Medicine 10.128.0.0/11 10.128.0.0 10.159.255.255 May be announced by Michigan Medicine
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 Sub-prefixes announced 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 10.255.0.0/16 special case in 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. No central 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
10.196.0.0/14 UMnet

Virtual Data Center service in the Amazon cloud (AWS). Approved 2017-11-21.

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 Michigan Medicine 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
10.223.0.0/16 UMnet Special cloud connections. Approved 2020-08-04.

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 [email protected] to activate these private prefixes.

172.16.0.0/12 Assignments

Backbone Prefix First Address Last Address Announcement Comments
Michigan Medicine 172.16.0.0/16 172.16.0.0 172.16.255.255 May be announced by Michigan Medicine  
Michigan Medicine 172.17.0.0/16 172.17.0.0 172.17.255.255 May be announced by Michigan Medicine  
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
Michigan Medicine 172.30.0.0/16 172.30.0.0 172.30.255.255 May be announced by Michigan Medicine 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 Sub-prefixes announced 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. Will never be routed across the core network. LAN-Local addresses have no central DNS or DHCP services.

192.168.0.0/16 Prefixes Announced by Mutual Agreement

Prefix Announced by Comments
none