Specifications

Parameter Defaults Description

Enable SPI and Yes The Intrusion Detection feature of the

Anti-DoS firewall Telephony Router limits the access of

protection 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 This option allows you to select different

Inspection 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

Discard Ping Disabled Prevents a ping on the router’s WAN port

from WAN Discard from being routed to the network.