Cyclades PR1000 User Manual
Page 89
89
Cyclades-PR1000
Chapter 12 - Filters and Rules
Exterior Router
The exterior router is the network’s first defense against attacks. For this reason, it is reasonable to prohibit all
packets except for those explicitly allowed. This is done by choosing the
Default Scope
to be
Deny
. Thus, ALL desired
traffic must be expressly allowed by the rules in the rule list.
Let
e-mail in
World of
Pos
sib
le
Pa
ck
ets
Let
e-mail out
DENY
DENY
DENY
Let Telnet
Connections Out
FIGURE 12.3 DENY AS DEFAULT SCOPE
In Figure 12.3, a conceptual equivalent of the interface is shown. All packets except those which fall into the holes
in the ball will be denied entry in to or out of the network.