Allied Telesis AlliedWare Plus Operating System Version 5.4.4C (x310-26FT,x310-26FP,x310-50FT,x310-50FP) - Manual (Page 2198)

Appendix B: Glossary
Software Reference for x310 Series Switches
B.8 AlliedWare Plus TM Operating System - Version 5.4.4C C613-50046-01 REV A
Designated bridge
Each bridge or LAN in the Spanning tree , except the Root bridge , has a unique parent,
known as the designated bridge. Each LAN has a single bridge, called the designated
bridge, that connects it to the next LAN on the path towards the root bridge.
For an overview of spanning tree operation see “Spanning tree operation” on
page 18.2 .
DHCP
Dynamic Host Configuration Protocol. A method of automatically allocating IP addresses.
A DHCP server holds a pool of IP addresses from which it draws individual ones as it
allocates them to users when they log on.
For more information see Chapter 63, Dynamic Host Configuration Protocol (DHCP)
Introduction .
DHCP Leasequery
The DHCP Leasequery protocol (RFC 4388) allows a device or process, for example a DHCP
relay agent, to obtain IP address information directly from the DHCP server using
DHCPLEASEQUERY messages.
For more information see “Enable DHCP Leasequery” on page 63.4 .
DHCP relay agent option 82
Enabling the DCHP Relay Agent Option 82 feature on the switch allows the switch to insert
extra information into the DHCP packets that it is relaying. The information is stored in a
specific optional field in the DHCP packet, namely, the agent-information field, which has
option ID 82.
Note that the DHCP Relay Agent Option 82 agent information inserted by the DHCP
snooping differs from the information added by DHCP Relay. The switch cannot be
configured to use both the DHCP relay agent option and DHCP snooping.
For information about the DHCP Relay Agent Option 82 information inserted by DHCP
snooping see
“DHCP Relay Agent Option 82” on page 55.4 .
DHCP relay agents
DHCP relay agents pass BOOTP and DHCP messages between servers and clients.
Networks where the DHCP or BOOTP server does not reside on the same IP subnet as its
clients need the intermediate routers to act as relay agents.
For information on how to configure the DHCP relay agent see “DHCP Relay Agent
Introduction” on page 63.7 .
DHCP snooping
DHCP snooping provides an extra layer of security on the switch via dynamic IP source
filtering. DHCP snooping filters out traffic received from unknown, or ‘untrusted’ ports,
and builds and maintains a DHCP snooping database.
With DHCP snooping, IP sources are dynamically verified, and filtered accordingly. IP
packets that are not sourced from recognized IP addresses can be filtered out. This ensures
the required traceability.
For more information see Chapter 55, DHCP Snooping Introduction and
Configuration . For a configuration example see “Configure DHCP Snooping” on
page 55.10 .