Alpha Telecom Arion 3100, User Manual

Page: 98 / 130

C
ONFIGURING THE
ADSL R
OUTER
4-36
Parameter Defaults Description
Enable SPI and
Anti-DoS firewall
protection
Yes The Intrusion Detection feature of the ADSL
Router limits the access of incoming traffic at the
WAN port. When the Stateful Packet Inspection
(SPI) feature is turned on, all incoming packets are
blocked except those types marked with a check in
the Stateful Packet Inspection section at the top of
the screen.
Stateful Packet
Inspection
This option allows you to select different
application types that are using dynamic port
numbers. If you wish to use Stateful Packet
Inspection (SPI) for blocking packets, click on the
Yes radio button in the “Enable SPI and Anti-DoS
firewall protection” field and then check the
inspection type that you need, such as Packet
Fragmentation, TCP Connection, UDP Session,
FTP Service, H.323 Service, and TFTP Service.
It is called a “stateful” packet inspection because it
examines the contents of the packet to determine
the state of the communication; i.e., it ensures that
the stated destination computer has previously
requested the current communication. This is a
way of ensuring that all communications are
initiated by the recipient computer and are taking
place only with sources that are known and trusted
from previous interactions. In addition to being
more rigorous in their inspection of packets,
stateful inspection firewalls also close off ports
until a connection to the specific port is requested.
When particular types of traffic are checked, only
the particular type of traffic initiated from the
internal LAN will be allowed. For example, if the
user only checks FTP Service in the Stateful Packet
Inspection section, all incoming traffic will be
blocked except for FTP connections initiated from
the local LAN.
Hacker Prevention
Feature
Discard Ping from
WAN
Discard Prevents a ping on the router’s WAN port from
being routed to the network.