24 May 2011

Private IP address ranges and the APIPA

Certain IP address ranges have been reserved for private network use.  These are listed in RFC 1918 http://tools.ietf.org/html/rfc1918.  These ranges can safely be used for internal networks.

Microsoft has also allocated a block of addresses called the Automatic Private IP Addressing (APIPA)  These are used by machines when no IP has been allocated and DHCP is not available. These auto allocted IPs are tomporary and will be superced as soon as a DHCP address becomes available.  http://support.microsoft.com/kb/220874



IP
Range Start

IP
Range End

Number
of hosts

CIDR

Subnet

Name

10.0.0.0

10.255.255.255

16 777 216

10.0.0.0/8

255.0.0.0

24-bit block

172.16.0.0

172.31.0.0

1 048 576

172.16.0.0/12

255.240.0.0

20-bit block

192.168.0.0

192.168.255.255

65 536

192.168.0.0/16

255.255.0.0

16-bit block

169.254.0.0

169.254.255.255

65 536

169.254.0.0/16

255.255.0.0

APIPA


When building lab or setting up new environments use the table as a guide to pick Which black or IPs or even part of the block that you want to use.  Bearing in mind that the some of address may already be route-able in your private network.

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