Why local addresses usually start with 192.168? [duplicate]

Question

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Why are home networks prefixed with 192.168?

Why local network addresses usually are like 192.168.xxx.xxx? Is there any reason they start with 192.168 or is it just a convention?

Answer 1

Convention, see RFC 1918:

The Internet Assigned Numbers Authority (IANA) has reserved the following three blocks of the IP address space for private internets:

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)

Out of these blocks the 192.168.0.0/16 is most often used as the default for home routers because it consists of 256 class C networks which all have the default netmask of 255.255.255.0. The other blocks are a class A and 16 class B networks which makes them less suitable for consumer grade devices because of the different netmask required.

See also Wikipedia:Private Network which is not authoritative, but gives a nice overview.