Asus SL1200 - Manual (Page 75)

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Chapter 9 - Configuring Firewall/NAT Settings
ASUS SL1200
9 Configuring Firewall/NAT Settings
The router provides built-in firewall/NAT functions. These functions protect
the system against denial of service (DoS) attacks and other types of
malicious accesses to your LAN while providing Internet access sharing at
the same time. You can also specify how to monitor attempted attacks, and
who should be automatically notified.
This chapter describes how to create/modify/delete Access Control List
(ACL) rules to control the data passing through your network. You will use
firewall configuration pages to:
• Create, modify, delete, and view inbound/outbound ACL rules.
• Create, modify, and delete pre-defined services, IP pools, NAT pools,
application filters and time ranges to be used in inbound/outbound
ACL configurations.
• View firewall statistics.
When you define an ACL rule, you instruct the Internet
Security Router to examine each data packet it receives
to determine whether it meets the criteria set in the rule.
The criteria can include the network or internet protocol it is
carrying, the direction in which it is traveling (for example,
from the LAN to the Internet or vice versa), the IP address of
the sending computer, the destination IP address, and other
characteristics of the packet data. If the packet matches
the criteria established in a rule, the packet can either be
accepted (forwarded towards its destination), or denied
(discarded), depending on the action specified in the rule.
9.1 Firewall Overview
9.1.1 Stateful Packet Inspection
The stateful packet inspection engine in the router maintains a state
table that is used to keep track of connection states of all the packets
passing through the firewall. The firewall will open a “hole” to allow the
packet to pass through if the state of the packet that belongs to an already
established connection matches the state maintained by the stateful