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Chapter 10 Firewalls
NN47923-500
Packet filtering firewalls
Packet filtering firewalls restrict access based on the source or destination
computer network address of a packet and the type of application.
Application level firewalls
Application level firewalls restrict access by serving as proxies for external
servers. Because they use programs written for specific Internet services, such as
HTTP, FTP and Telnet, they can evaluate network packets for valid application
specific data. Application level firewalls have a number of general advantages
over the default mode of permitting application traffic directly to internal hosts:
1
Information hiding prevents the names of internal systems from being made
known through DNS to outside systems, because the application gateway is
the only host whose name must be made known to outside systems.
2
Robust authentication and logging preauthenticates application traffic before
it reaches internal hosts and causes it to be logged more effectively than if it
were logged with standard host logging. Filtering rules at the packet filtering
router can be less complex than if the router needed to filter application traffic
and direct it to a number of specific systems. The router need only allow
application traffic destined for the application gateway and reject the rest.
Stateful Inspection firewalls
Stateful inspection firewalls restrict access by screening data packets against
defined access rules. They make access control decisions based on IP address and
protocol. They also inspect the session data to assure the integrity of the
connection and to adapt to dynamic protocols. These firewalls generally provide
the best speed and transparency; however, they often lack the granular application
level access control or caching that some proxies support. For more information,
see
“Stateful inspection” on page 161
Firewalls, of one type or another, have become an integral part of standard
security solutions for enterprises.
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 ...