Vigitron MaxiiNet Vi30126 Series, Operation Manual

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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). 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.
DNS
DNS is an acronym for Domain Name System. It stores and associates many
types of information with domain names. Most importantly, DNS translates
human-friendly domain names and computer hostnames into computer-friendly
IP addresses. For example, the domain name www.example.com might translate
to 192.168.0.1.
DoS
DoS is an acronym for Denial of Service. In a denial-of-service (DoS) attack, an
attacker attempts to prevent legitimate users from accessing information or
services. By targeting at network sites or network connection, an attacker may be
able to prevent network users from accessing email, web sites, online accounts
(banking, etc.), or other services that rely on the affected computer.
Dotted
Decimal
Notation
Dotted Decimal Notation refers to a method of writing IP addresses using decimal
numbers and dots as separators between octets.
An IPv4 dotted decimal address has the form x.y.z.w, where x, y, z, and w are
decimal numbers between 0 and 255.