FCD-IPM Installation and Operation Manual Chapter 5 Setup Menu
WAN Economy Menu 5-83
FCD-IPM
Link
Traffic is Regulated Link to LAN Filter
LAN to Link Filter
Traffic is Regulated
Figure 5-87. Action of an Advanced Filter
There are two modes through which filtering can be implemented: blocking and
forwarding.
Blocking The block command causes FCD-IPM to test every packet of data that is sent to or
from the LAN. If the packet passes the test, passage is denied.
Example:
You want to ensure that IP/UDP packets do not go on to the link in the direction
of the Internet/Intranet. Thus, you design a filter, which tests each packet to see if
it is an IP/UDP packet. If the packet tests positive, it is automatically blocked.
Forwarding The forward command works in the same way as the block command. However,
with forwarding, if the packet passes the test, the packet is allowed to pass to or
from the LAN.
Example:
To allow a certain user on the Small Office LAN to access the Internet for FTP
purposes, create a filter to test each packet for the IP host address of the specified
user and the FTP socket of the packet. If the packet passes the test, the packet is
forwarded to the Internet/Intranet.
Multiple Filters
Up to 18 filters can be defined. If there are 2 filters that have contradictory
operations, forwarding takes precedence over blocking.
Example:
You want to allow only one particular user on the Small Office LAN to access the
Internet for FTP purposes. To insure that no one else is able to access the Internet,
create a blocking filter for all traffic going to the link. To do this, from the Blocking
and Forwarding menu enter Block all traffic for Link1. In addition, create a filter to
test each packet for the IP host address of the specified user and the FTP socket of
the packet. Since forwarding takes precedence over blocking, that user's frames are
forwarded.