Private ip addresses – NETGEAR PS100 User Manual

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122

6

252

7

254

8

255

The next table displays several common netmask values in both the dotted-decimal and the masklength

formats.

Netmask Formats

Dotted-Decimal Masklength

255.0.0.0

/8

255.255.0.0

/16

255.255.255.0

/24

255.255.255.128 /25

255.255.255.192 /26

255.255.255.224 /27

255.255.255.240 /28

255.255.255.248 /29

255.255.255.252 /30

255.255.255.254 /31

255.255.255.255 /32

NETGEAR strongly advises that all hosts on a LAN segment use the same netmask for the following

reasons:

So that hosts recognize local IP broadcast packets

When a device broadcasts to its segment neighbors, it uses a destination address of the local network

address with all ones for the host address. In order for this scheme to work, all devices on the segment must

agree on which bits comprise the host address.

So that a local router or bridge will know which addresses are local and which are remote

Private IP Addresses

If your networks are isolated from the Internet (for example, only between your two branch offices),

you can assign any IP addresses to the hosts without problems. However, the IANA has reserved the

following three blocks of IP addresses specifically for private networks:

10.0.0.0 - 10.255.255.255

172.16.0.0 - 172.31.255.255

192.168.0.0 - 192.168.255.255

NETGEAR recommends that you choose your private network number from this list.

Regardless of your particular situation, do not create an arbitrary IP address; always follow the

guidelines explained here. For more information about address assignment, refer to RFC 1918, Address

Allocation for Private Internets, and RFC 2050, Guidelines for Management of IP Address Space .

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