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Appendix A: Firewall
Stateful Packet Inspection
Refers to an architecture, where the firewall keeps track of packets on each
connection traversing all its interfaces and makes sure they are valid. This is in
contrast to static packet filtering which only examines a packet based on the
information in the packet header.
Denial of Service attack
Is an incident in which a user or organization is deprived of the services of a
resource they would normally expect to have. Various DoS attacks the device can
withstand are: ARP Attack, Ping Attack, Ping of Death, Land, SYN Attack, Smurf
Attack and Tear Drop.
TCP/IP/Port/Interface filtering rules
These rules help in the filtering of traffic at the Network layer i.e. Layer 3.
When a Routing interface is created "Enable Firewall" must be checked.
Navigate to Advanced Setup -> Security -> IP Filtering, web page.
Outgoing IP Filtering: Helps in setting rules to DROP packets from the LAN
interface. By default if Firewall is Enabled all IP traffic from LAN is allowed. By
setting up one or more filters, particular packet types coming from the LAN can be
dropped.
Filter Name: User defined Filter Name.
Protocol: Can take on any values from: TCP/UDP, TCP, UDP or ICMP
Source IP Address/Source Subnet Mask: Packets with the particular "Source
IP Address/Source Subnet Mask" combination will be dropped.
Source Port: This can take on either a single port number or a range of port
numbers. Packets having a source port equal to this value or falling within the range
of port numbers(portX : portY) will be dropped.
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