FibroLAN Falcon-RX/812/G/A User Manual page 319

Falcon R-Class | User Guide
DES
DES is an acronym for Data Encryption Standard. It provides a complete description of a
mathematical algorithm for encrypting (enciphering) and decrypting (deciphering) binary coded
information.
Encrypting data converts it to an unintelligible form called cipher. Decrypting cipher converts the
data back to its original form called plaintext. The algorithm described in this standard specifies both
enciphering and deciphering operations which are based on a binary number called a key.
DHCP
DHCP is an acronym for Dynamic Host Configuration Protocol. It is a protocol used for assigning
dynamic IP addresses to devices on a network.
DHCP used by networked computers (clients) to obtain IP addresses and other Parameters such as
the default gateway, subnet mask, and IP addresses of DNS servers from a DHCP server.
The DHCP server ensures that all IP addresses are unique, for example, no IP address is assigned to
a second client while the first client's assignment is valid (its lease has not expired). Therefore, IP
address pool management is done by the server and not by a human network administrator.
Dynamic addressing simplifies network administration because the software keeps track of IP
addresses rather than requiring an administrator to manage the task. This means that a new
computer can be added to a network without the hassle of manually assigning it a unique IP address.
DHCP Relay
DHCP Relay is used to forward and to transfer DHCP messages between the clients and the server
when they are not on the same subnet domain.
The DHCP option 82 enables a DHCP relay agent to insert specific information into a DHCP request
packets when forwarding client DHCP packets to a DHCP server and remove the specific information
from a DHCP reply packets when forwarding server DHCP packets to a DHCP client. The DHCP server
can use this information to implement IP address or other assignment policies. Specifically the option
works by setting two sub-options: Circuit ID (option 1) and Remote ID (option2). The Circuit ID sub-
option is supposed to include information specific to which circuit the request came in on. The
Remote ID sub-option was designed to carry information relating to the remote host end of the
circuit.
The definition of Circuit ID in the switch is 4 bytes in length and the format is "vlan_id" "module_id"
"port_no". The parameter of "vlan_id" is the first two bytes represent the VLAN ID. The parameter
of "module_id" is the third byte for the module ID (in standalone switch it always equal 0, in stackable
switch it means switch ID). The parameter of "port_no" is the fourth byte and it means the port
number.
The Remote ID is 6 bytes in length, and the value is equal the DHCP relay agents MAC address.
DHCP Snooping
DHCP Snooping is used to block intruder on the untrusted ports of the switch device when it tries to
intervene by injecting a bogus DHCP reply packet to a legitimate conversation between the DHCP
client and server.
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