D-Link DXS-3250E - xStack Switch, Web/Installation Manual

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DXS-3227, DXS-3227P, DXS-3250 and DXS-3250E EWS User Guide
Page 384
Feature Description
DHCP Snooping DHCP snooping is a DHCP security feature that provides network
security by filtering un-trusted DHCP messages and by building
and maintaining a DHCP snooping binding database, also
referred to as a DHCP snooping binding table. DHCP snooping
acts like a firewall between untrusted hosts and DHCP servers.
DHCP option 82 Relay agent information option (option-82) in the DHCP protocol
enables a DHCP relay agent or DHCP snooping switch to insert
the port number of a client into the DHCP DISCOVER message.
The Relay agent information option specifies the port number
from which the client’s packet was received.
Domain Name System Domain Name System (DNS) converts user-defined domain
names into IP addresses. Each time a domain name is assigned
the DNS service translates the name into a numeric IP address.
For example, www.ipexample.com is translated to 192.87.56.2.
DNS servers maintain domain name databases and their
corresponding IP addresses.
Dynamic ARP Inspection ARP header inspection check on un-trusted ports, checking IP-
MAC binding. (For preventing ARP spoofing attacks)
ARP provides IP communication within a Layer 2 broadcast
domain by mapping an IP address to a MAC address. However,
because ARP allows a gratuitous reply from a host even if an
ARP request was not received, an ARP spoofing attack and the
poisoning of ARP caches can occur. After the attack, all traffic
from the device under attack flows through the attacker’s
computer and then to the router, switch, or host.
Fast Link STP can take up to 30-60 seconds to converge. During this time,
STP detects possible loops, allowing time for status changes to
propagate and for relevant devices to respond. 30-60 seconds is
considered too long of a response time for many applications.
The Fast Link option bypasses this delay, and can be used in net-
work topologies where forwarding loops do not occur.
Full 802.1Q VLAN Tagging Compliance IEEE 802.1Q defines an architecture for virtual bridged LANs, the
services provided in VLANs and the protocols and algorithms
involved in the provision of these services. An important
requirement included in this standard is the ability to mark frames
with a desired Class of Service (CoS) tag value.
GVRP Support GARP VLAN Registration Protocol (GVRP) provides IEEE
802.1Q-compliant VLAN pruning and dynamic VLAN creation on
802.1Q trunk ports. When GVRP is enabled, the device registers
and propagates VLAN membership on all ports that are part of the
active underlying Spanning Tree Protocol Features topology.