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Page 181 / 320 Scroll up to view Page 176 - 180
Chapter 15 Firewall
AMG1302/AMG1202-TSeries User’s Guide
181
15.4.2
Customized Services
Configure customized services and port numbers not predefined by the AMG1302/AMG1202-
TSeries. For a comprehensive list of port numbers and services, visit the IANA (Internet Assigned
Number Authority) website. See
Appendix F on page 305
for some examples. Click the
Edit
Customized Services
button while editing a firewall rule to configure a custom service port. This
displays the following screen.
Address Type
Do you want your rule to apply to packets with a particular (single) IP, a range of IP
addresses (for instance, 192.168.1.10 to 192.169.1.50), a subnet or any IP address?
Select an option from the drop-down list box that includes:
Single Address
,
Range
Address
,
Subnet Address
and
Any
Address
.
Start IP Address
Enter the single IP address or the starting IP address in a range here.
End IP Address
Enter the ending IP address in a range here.
Subnet Mask
Enter the subnet mask here, if applicable.
Source Mac Address
Specify a source MAC address of traffic to which to apply this firewall rule applies.
Please note that a blank source MAC address is equivalent to any.
Source Interface
Specify a source interface to which this firewall rule applies. This is the interface
through which the traffic entered the AMG1302/AMG1202-TSeries. Please note that a
blank source interface is equivalent to any.
Destination Interface
Specify a destination interface to which this firewall rule applies. This is the interface
through which the traffic is destined to leave the AMG1302/AMG1202-TSeries. Please
note that a blank source interface is equivalent to any.
Services
Available Services
Please see
Appendix F on page 305
for more information on services available. Select
a service from the
Available Services
box.
Edit Customized
Service
Click the
Edit Customized Service
button to bring up the screen that you use to
configure a new custom service that is not in the predefined list of services.
TCP Flag
Specify any TCP flag bits the firewall rule is to check for.
Schedule
Select the days and time during which to apply the rule. Select
Everyday
and
All
Day
to always apply the rule.
Apply
Click this to save your changes.
Cancel
Click this to restore your previously saved settings.
Table 63
Security > Firewall > Rules > Add
LABEL
DESCRIPTION
Page 182 / 320
Chapter 15 Firewall
AMG1302/AMG1202-TSeries User’s Guide
182
Figure 85
Security > Firewall > Rules: Edit: Edit Customized Services
The following table describes the labels in this screen.
15.4.3
Customized Service Add/Edit
Use this screen to add a customized rule or edit an existing rule. Click
Add
or the
Edit
icon next to
a rule number in the
Firewall Customized Services
screen to display the following screen.
Figure 86
Security > Firewall > Rules: Edit: Edit Customized Services: Add/Edit
Table 64
Security > Firewall > Rules: Edit: Edit Customized Services
LABEL
DESCRIPTION
#
This is the number of your customized port.
Name
This is the name of your customized service.
Protocol
This shows the IP protocol (
TCP
or
UDP
) that defines your customized service.
Port Type
This is the port number or range that defines your customized service.
Start Port
This is a single port number or the starting port number of a range that defines your
customized service.
End Port
This is a single port number or the ending port number of a range that defines your customized
service.
Modify
Click this to edit a customized service.
Add
Click this to configure a customized service.
Back
Click this to return to the
Firewall Edit Rule
screen.
Page 183 / 320
Chapter 15 Firewall
AMG1302/AMG1202-TSeries User’s Guide
183
The following table describes the labels in this screen.
Table 65
Security > Firewall > Rules: Edit: Edit Customized Services: Add/Edit
LABEL
DESCRIPTION
Config
Service Name
Type a unique name for your custom port.
Service Type
Choose the IP port (
TCP
or
UDP
) that defines your customized port from the drop down list
box.
Port Configuration
Type
Click
Single
to specify one port only or
Port Range
to specify a span of ports that define
your customized service.
Port Number
Type a single port number or the range of port numbers that define your customized
service.
Back
Click this to return to the previous screen without saving.
Apply
Click this to save your changes.
Cancel
Click this to restore your previously saved settings.
Delete
Click this to delete the current rule.
Page 184 / 320
Chapter 15 Firewall
AMG1302/AMG1202-TSeries User’s Guide
184
15.5
The DoS Screen
Use this screen to enable DoS protection. Click
Security > Firewall > Dos
to display the following
screen.
Figure 87
Security > Firewall > Dos
The following table describes the labels in this screen.
15.5.1
The DoS Advanced Screen
For DoS
attacks, the AMG1302/AMG1202-TSeries uses thresholds to determine when to start
dropping sessions that do not become fully established (half-open sessions). These thresholds
apply globally to all sessions.
For TCP, half-open means that the session has not reached the established state-the TCP three-way
handshake has not yet been completed. Under normal circumstances, the application that initiates
a session sends a SYN (synchronize) packet to the receiving server. The receiver sends back an ACK
(acknowledgment) packet and its own SYN, and then the initiator responds with an ACK
(acknowledgment). After this handshake, a connection is established.
Figure 88
Three-Way Handshake
For UDP, half-open means that the firewall has detected no return traffic. An unusually high number
(or arrival rate) of half-open sessions could indicate a DOS attack.
Table 66
Security > Firewall > Dos
LABEL
DESCRIPTION
Denial of Services
Enable this to protect against DoS attacks. The AMG1302/AMG1202-TSeries will drop
sessions that surpass maximum thresholds.
Apply
Click this to save your changes.
Cancel
Click this to restore your previously saved settings.
Advanced
Click this to go to a screen to specify maximum thresholds at which the AMG1302/
AMG1202-TSeries will start dropping sessions.
Page 185 / 320
Chapter 15 Firewall
AMG1302/AMG1202-TSeries User’s Guide
185
15.5.1.1
Threshold Values
If everything is working properly, you probably do not need to change the threshold settings as the
default threshold values should work for most small offices. Tune these parameters when you
believe the AMG1302/AMG1202-TSeries has been receiving DoS attacks that are not recorded in
the logs or the logs show that the AMG1302/AMG1202-TSeries is classifying normal traffic as DoS
attacks. Factors influencing choices for threshold values are:
1
The maximum number of opened sessions.
2
The minimum capacity of server backlog in your LAN network.
3
The CPU power of servers in your LAN network.
4
Network bandwidth.
5
Type of traffic for certain servers.
Reduce the threshold values if your network is slower than average for any of these factors
(especially if you have servers that are slow or handle many tasks and are often busy).
•
If you often use P2P applications such as file sharing with eMule or eDonkey, it’s recommended
that you increase the threshold values since lots of sessions will be established during a small
period of time and the AMG1302/AMG1202-TSeries may classify them as DoS attacks.
15.5.2
Configuring Firewall Thresholds
Click
Security > Firewall > DoS > Advanced
to display the following screen.
Figure 89
Security > Firewall > DoS > Advanced

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