D-Link NetDefend DFL-1660, User Manual

Page: 562 / 595

13.4. State Settings
Connection Replace
Allows new additions to the NetDefendOS connection list to replace the oldest connections if there
is no available space.
Default: ReplaceLog
Log Open Fails
In some instances where the Rules section determines that a packet should be allowed through, the
stateful inspection mechanism may subsequently decide that the packet cannot open a new
connection. One example of this is a TCP packet that, although allowed by the Rules section and not
being part of an established connection, has its SYN flag off. Such packets can never open new
connections. In addition, new connections can never be opened by ICMP messages other than ICMP
ECHO (Ping). This setting determines if NetDefendOS is to log the occurrence of such packets.
Default: Enabled
Log Reverse Opens
Determines if NetDefendOS logs packets that attempt to open a new connection back through one
that is already open. This only applies to TCP packets with the SYN flag turned on and to ICMP
ECHO packets. In the case of other protocols such as UDP, there is no way of determining whether
the remote peer is attempting to open a new connection.
Default: Enabled
Log State Violations
Determines if NetDefendOS logs packets that violate the expected state switching diagram of a
connection, for example, getting TCP FIN packets in response to TCP SYN packets.
Default: Enabled
Log Connections
Specifies how NetDefendOS, will log connections:
• NoLog – Does not log any connections; consequently, it will not matter if logging is enabled for
either Allow or NAT rules in the IP rule set; they will not be logged. However, FwdFast, Drop
and Reject rules will be logged as stipulated by the settings in the Rules section.
• Log – Logs connections in short form; gives a short description of the connection, which rule
allowed it to be made and any SAT rules that apply. Connections will also be logged when they
are closed.
• LogOC – As for Log, but includes the two packets that cause the connection to be opened and
closed. If a connection is closed as the result of a timeout, no ending packet will be logged
• LogOCAll – Logs all packets involved in opening and closing the connection. In the case of
TCP, this covers all packets with SYN, FIN or RST flags turned on
• LogAll – Logs all packets in the connection.
13.4. State Settings Chapter 13. Advanced Settings
562