
Chapter 10 Firewalls
165
Nortel Business Secure Router 222 Configuration — Basics
3
The packet is inspected by a firewall rule to determine and record information
about the state of the packet's connection. This information is recorded in a
new state table entry created for the new connection. If there is not a firewall
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.
Содержание BSR222
Страница 28: ...28 Tables NN47922 500 ...
Страница 50: ...50 Chapter 2 Introducing the WebGUI NN47922 500 ...
Страница 66: ...66 Chapter 3 Wizard setup NN47922 500 ...
Страница 87: ...Chapter 5 System screens 87 Nortel Business Secure Router 222 Configuration Basics Figure 17 Time and Date ...
Страница 92: ...92 Chapter 5 System screens NN47922 500 ...
Страница 96: ...96 Chapter 6 LAN screens NN47922 500 Configuring IP Click LAN to open the IP screen Figure 19 LAN IP ...
Страница 104: ...104 Chapter 6 LAN screens NN47922 500 ...
Страница 115: ...Chapter 7 WAN screens 115 Nortel Business Secure Router 222 Configuration Basics Figure 27 WAN IP ...
Страница 123: ...Chapter 7 WAN screens 123 Nortel Business Secure Router 222 Configuration Basics Figure 32 Dial Backup Setup ...
Страница 154: ...154 Chapter 9 Static Route screens NN47922 500 ...
Страница 196: ...196 Chapter 11 Firewall screens NN47922 500 ...
Страница 212: ...212 Chapter 13 VPN NN47922 500 Figure 68 Summary IP Policies ...
Страница 223: ...Chapter 13 VPN 223 Nortel Business Secure Router 222 Configuration Basics Figure 72 VPN Branch Office rule setup ...
Страница 249: ...Chapter 13 VPN 249 Nortel Business Secure Router 222 Configuration Basics Figure 79 VPN Client Termination ...
Страница 256: ...256 Chapter 13 VPN NN47922 500 Figure 82 VPN Client Termination advanced ...
Страница 260: ...260 Chapter 13 VPN NN47922 500 ...
Страница 264: ...264 Chapter 14 Certificates NN47922 500 Figure 84 My Certificates ...
Страница 273: ...Chapter 14 Certificates 273 Nortel Business Secure Router 222 Configuration Basics Figure 87 My Certificate details ...
Страница 281: ...Chapter 14 Certificates 281 Nortel Business Secure Router 222 Configuration Basics Figure 90 Trusted CA details ...
Страница 290: ...290 Chapter 14 Certificates NN47922 500 Figure 95 Trusted remote host details ...
Страница 314: ...314 Chapter 16 IEEE 802 1x NN47922 500 ...
Страница 318: ...318 Chapter 17 Authentication server NN47922 500 Figure 107 Local User database edit ...
Страница 326: ...326 Chapter 17 Authentication server NN47922 500 ...
Страница 374: ...374 Chapter 20 Logs Screens NN47922 500 Figure 151 Log settings ...
Страница 384: ...384 Chapter 20 Logs Screens NN47922 500 ...
Страница 390: ...390 Chapter 21 Call scheduling screens NN47922 500 Figure 158 Applying Schedule Sets to a remote node ...
Страница 402: ...402 Chapter 22 Maintenance NN47922 500 Figure 170 Restart screen ...
Страница 422: ...422 Appendix A Troubleshooting NN47922 500 ...