Glossary
GL-22
Cisco Router and Security Device Manager 2.5 User’s Guide
OL-4015-12
mask
subnet mask
netmask
network mask
A 32-bit bit mask which specifies how an Internet address is to be divided into
network, subnet, and host parts. The net mask has ones (1’s) in the bit positions
in the 32-bit address that are to be used for the network and subnet parts, and has
zeros (0’s) for the host part. The mask should contain at least the standard
network portion (as determined by the address class), and the subnet field should
be contiguous with the network portion. The mask is configured using the
decimal equivalent of the binary value.
Examples:
Decimal: 255.255.255.0
Binary: 11111111 11111111 11111111 00000000
The first 24 bits provide the network and subnetwork address, and the last 8
provide the host address.
Decimal: 255.255.255.248
Binary: 11111111 11111111 11111111 11111000
The first 29 bits provide the network and subnetwork address, and the last 3
provide the host address.
See also IP Address, TCP/IP, host, host/network.
MD5 Message Digest 5. A one-way hashing function that produces a 1 28-bit hash.
Both MD5 and Secure Hashing Algorithm (SHA) are variations on MD4 and are
designed to strengthen the security of the MD4 hashing algor ithm. Cisco uses
hashes for authentication within the IPSec framework. MD5 verifies the
integrity and authenticates the origin of a communication.
message digest A string of bits that represents a larger data block. This string defines a data
block, based on the processing of its precise content through a 128-bit hash
function. Message digests are used in the generation of digital signatures. See
hash.
MD5 Message Digest 5. A one-way hashing algorithm that produces a 128-bit hash.
Both MD5 and Secure Hash Algorithm (SHA) are variations on MD4 and are
designed to strengthen the security of the MD4 hashing algor ithm. Cisco uses
hashes for authentication within the IPSec framework. Also used for message
authentication in SNMP v.2. MD5 verifies the integrity of the communication,
authenticates the origin, and checks for timeliness.