D-Link DFL-2500 - Manual (Page 190)

The console command
> updatecenter -status
will show the current status of the auto-update feature. This can also be done through the WebUI.
Updating in High Availability Clusters
Updating the IDP databases for both the D-Link Firewalls in an HA Cluster is performed
automatically by NetDefendOS. In a cluster there is always an active unit and an inactive unit. Only
the active unit in the cluster will perform regular checking for new database updates. If a new
database update becomes available the sequence of events will be as follows:
1. The active unit determines there is a new update and downloads the required files for the
update.
2. The active unit performs an automatic reconfiguration to update its database.
3. This reconfiguration causes a failover so the passive unit becomes the active unit.
4. When the update is completed, the newly active unit also downloads the files for the update
and performs a reconfiguration.
5. This second reconfiguration causes another failover so the passive unit reverts back to being
active again.
These steps result in both D-Link Firewalls in a cluster having updated databases and with the
original active/passive roles. For more information about HA clusters refer to Chapter 11, High
Availability.
6.5.3. IDP Rules
Rule Components
An IDP Rule defines what kind of traffic, or service, should be analyzed. An IDP Rule is similar in
makeup to an IP Rule. IDP Rules are constructed like other security policies in NetDefendOS such
as IP Rules. An IDP Rule specifies a given combination source/destination interfaces/addresses as
well as being associated with a Service object which defines which protocols to scan. A time
schedule can also be associated with an IDP Rule. Most importantly, an IDP Rule specifies the
Action to take on detecting an intrusion in the traffic targeted by the rule.
Initial Packet Processing
The initial order of packet processing with IDP is as follows:
1. A packet arrives at the firewall and NetDefendOS performs normal verification. If the packet is
part of a new connection then it is checked against the IP rule set before being passed to the
IDP module. If the packet is part of an existing connection it is passed straight to the IDP
system. If the packet is not part of an existing connection or is rejected by the IP rule set then it
is dropped.
2. The source and destination information of the packet is compared to the set of IDP Rules
defined by the administrator. If a match is found, it is passed on to the next level of IDP
processing which is pattern matching, described in step below. If there is no match against an
IDP rule then the packet is accepted and the IDP system takes no further actions although
further actions defined in the IP rule set are applied such as address translation, logging.
Checking Dropped Packets
6.5.3. IDP Rules Chapter 6. Security Mechanisms
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