Chapter 10 Firewalls
163
Nortel Business Secure Router 252 Configuration — Basics
rule for this packet and it is not an attack, the
Action for packets that don’t
match firewall rules
field determines the action for this packet.
4
Based on the obtained state information, a firewall rule creates a temporary
access list entry that is inserted at the beginning of the WAN interface's
inbound extended access list. This temporary access list entry is designed to
permit inbound packets of the same connection as the outbound packet just
inspected.
5
The outbound packet is forwarded out through the interface.
6
Later, an inbound packet reaches the interface. This packet is part of the
connection previously established with the outbound packet. The inbound
packet is evaluated against the inbound access list, and is permitted because of
the temporary access list entry previously created.
7
The packet is inspected by a firewall rule, and the connection's state table
entry is updated as necessary. You can modify the inbound extended access
list temporary entries based on the updated state information, in order to
permit only packets that are valid for the current state of the connection.
8
Any additional inbound or outbound packets that belong to the connection are
inspected to update the state table entry and to modify the temporary inbound
access list entries as required, and are forwarded through the interface.
9
When the connection terminates or times out, the connection's state table
entry is deleted and the connection's temporary inbound access list entries are
deleted.
Stateful inspection and the Business Secure Router
Additional rules can be defined to extend or override the default rules. For
example, a rule can be created that will:
•
Block all traffic of a certain type, such as IRC (Internet Relay Chat), from the
LAN to the Internet.
•
Allow certain types of traffic from the Internet to specific hosts on the LAN.
•
Allow access to a Web server to everyone but competitors.
•
Restrict use of certain protocols, such as Telnet, to authorized users on the
LAN.
Summary of Contents for BSR252
Page 28: ...28 Tables NN47923 500 ...
Page 44: ...44 Chapter 1 Getting to know your Business Secure Router NN47923 500 ...
Page 52: ...52 Chapter 2 Introducing the WebGUI NN47923 500 ...
Page 70: ...70 Chapter 3 Wizard setup NN47923 500 ...
Page 96: ...96 Chapter 5 System screens NN47923 500 ...
Page 114: ...114 Chapter 7 WAN screens NN47923 500 Figure 27 WAN IP ...
Page 120: ...120 Chapter 7 WAN screens NN47923 500 Figure 31 Dial Backup Setup ...
Page 128: ...128 Chapter 7 WAN screens NN47923 500 ...
Page 152: ...152 Chapter 9 Static Route screens NN47923 500 ...
Page 194: ...194 Chapter 11 Firewall screens NN47923 500 ...
Page 210: ...210 Chapter 13 VPN NN47923 500 Figure 67 Summary IP Policies ...
Page 222: ...222 Chapter 13 VPN NN47923 500 Figure 71 VPN Branch Office rule setup ...
Page 256: ...256 Chapter 13 VPN NN47923 500 Figure 81 VPN Client Termination advanced ...
Page 260: ...260 Chapter 13 VPN NN47923 500 ...
Page 264: ...264 Chapter 14 Certificates NN47923 500 Figure 83 My Certificates ...
Page 270: ...270 Chapter 14 Certificates NN47923 500 Figure 85 My Certificate create ...
Page 274: ...274 Chapter 14 Certificates NN47923 500 Figure 86 My Certificate details ...
Page 282: ...282 Chapter 14 Certificates NN47923 500 Figure 89 Trusted CA details ...
Page 298: ...298 Chapter 14 Certificates NN47923 500 ...
Page 316: ...316 Chapter 16 IEEE 802 1x NN47923 500 ...
Page 320: ...320 Chapter 17 Authentication server NN47923 500 Figure 106 Local User database edit ...
Page 328: ...328 Chapter 17 Authentication server NN47923 500 ...
Page 376: ...376 Chapter 20 Logs Screens NN47923 500 Figure 150 Log settings ...
Page 386: ...386 Chapter 20 Logs Screens NN47923 500 ...
Page 393: ...Chapter 21 Call scheduling screens 393 Nortel Business Secure Router 252 Configuration Basics ...
Page 394: ...394 Chapter 21 Call scheduling screens NN47923 500 ...
Page 410: ...410 Chapter 22 Maintenance NN47923 500 ...