Lantronix SCS Reference Manual page 195

Security
Type of Filter List
Incoming
Outgoing
Startup
When a site with an associated filter list receives a packet, the SCS will compare the packet against each
filter starting with the first filter on the list. If the packet matches any of the filters, the packet will be
forwarded or discarded to the filter's specification. If the packet does not match any of the filters in the list,
it will not be forwarded.
11.6.5.1 Filter Order
The order that filters appear in a list is important. For example, consider the following filter list:
Allow any packets
Deny all IP traffic matching a particular rule
When this filter list is associated with a site, all packets will be forwarded. Packets will be compared to the
first filter in the list, and all packets will match specification "any packets." Therefore, all packets will be
forwarded without being compared to the second filter.
Switching the order of the two filters will have very different effects. Examine the filter list below, where
the order of the two filters is reversed.
Deny all IP traffic matching a particular rule
Allow any packets
When this filter list is used, any IP traffic matching the specified rule will be discarded. Therefore, some IP
packets will be discarded without being compared to the second filter.
11.6.5.2 Preventing All IP Traffic
To prevent all IP packet traffic, you do not need to use a filter list. Instead, use the Define Site IP Disabled
command.
Local>> DEFINE SITE irvine IP DISABLED
11.6.5.3 Setting Up a Filter List
Configuring filter lists involves two primary steps: creating the filter list, and associating the list with a
particular site.
Table 11-1: Types of Filter Lists
Purpose
Determines whether to forward incoming packets received
from a remote site. Packets that pass the filter will be
forwarded.
Determines whether to forward outgoing packets to a remote
site. Packets that pass the filter will be forwarded.
Determines whether a site will initiate a connection to a
remote site. When a packet passes the filter, the SCS will
initiate an outgoing connection. (If an outgoing connection
currently exists, this filter will be ignored.)
Figure 11-47: Preventing IP Packet Traffic
11-24
Network Restrictions