User manual

51
Internet
3
4
SMTP Client
SMTP Server
172.16.1.1:1357 192.168.3.4:25
Firewall
Packet Direction Source Destination Protocol Dest. Port Action (Rule)
5 Inbound 10.1.2.3 171.16.3.4 TCP 6000 Deny (E)
6 Outbound 171.16.3.4 10.1.2.3 TCP 5150 Deny (E)
Internet
5
6
Attacker
171.16.3.4:6000 10.1.2.3:5150
Firewall
X11 Server
Update Filtering Rule
Index Protocol Direction Action Source Destination Source Port Dest. Port
1 TCP Inbound Permit External Internal >1023 25
2 TCP Outbound Permit Internal External 25 >1023
3 TCP Outbound Permit Internal External >1023 25
4 TCP Inbound Permit External Internal 25 >1023
5 Any Either Deny Any Any Any Any
Filtering Result
Index Protocol Direction Action Source Destination Source Port Dest. Port
1 TCP Inbound Permit(A) 192.168.3.4 171.16.1.1 1234 25
2 TCP Outbound Permit(B) 171.16.1.1 192.168.3.4 25 1234
3 TCP Outbound Permit(C) 171.16.1.1 192.168.3.4 1357 25
4 TCP Inbound Permit(D) 192.168.3.4 171.16.1.1 25 1357
5 TCP Inbound Deny(E) 10.1.2.3 171.16.3.4 5150 6000
6 TCP Outbound Deny(E) 171.16.3.4 10.1.2.3 6000 5150
Rule Order
The rules order affects the filtering result. The filtering process will proceed from top to bottom,
changing the order as the different result of filtering.
Rule Source Address Destination Address Action
A 10.0.0.0 172.16.6.0 Permit
B 10.1.99.0 172.16.0.0 Deny
C Any Any Deny
Where “0” at the last eight bits indicates “from 1 to 254”, “0” at any eight bits preceding “0”, “0.0” or
“0.0.0” indicates “from 1 to 254”. On the other hand, “0” and all “0” successive with “0” represents any.
When the rule is ordered as ABC.
Index Source Address Destination Address Action
1 10.1.99.1 172.16.1.1 Deny (B)