Nortel Meridian 1 Description, Installation And Operation page 259

$SSHQGL[#&= 6XEQHW#PDVN#FRQYHUVLRQ
IURP#&,'5#WR#GRWWHG
GHFLPDO#IRUPDW
Subnet masks may be expressed in Classless Inter Domain Routing (CIDR)
format, appended to the IP address. For example 10.1.1.1/20. The subnet
mask must be converted from CIDR format to dotted decimal format in order
to configure IP addresses.
CIDR format expresses the subnet mask as the number of bits counting from
the most significant bit of the first IP address field. A complete IP address
consists of 32 bits. Therefore, a typical CIDR format subnet mask will be in
the range from /9 to /30. Each decimal number field in the dotted decimal
format can have a value from 0 to 255, where decimal 255 represents binary
1111 1111.
To convert the subnet mask from CIDR format to dotted decimal format:
1 Divide the CIDR format value by 8. The quotient (the number of times
that eight divides into the CIDR format value) equals the number of
dotted decimal fields containing 255.
In the example above, the subnet mask is expressed as /20. Twenty
divided by eight equals a quotient of two, with a remainder of four.
Therefore, the first two fields of the subnet mask in dotted decimal
format are 255.255.
ITG Line 1.0/IP Telecommuter Description, Installation and Operation
Page 259 of 262