Chapter 10 Firewalls
P-660HWP-Dx User’s Guide
41
are allowed in. The P-660HWP-Dx uses stateful packet inspection to protect the private LAN
from hackers and vandals on the Internet. By default, the P-660HWP-Dx’s stateful inspection
allows all communications to the Internet that originate from the LAN, and blocks all traffic to
the LAN that originates from the Internet. In summary, stateful inspection:
• Allows all sessions originating from the LAN (local network) to the WAN (Internet).
• Denies all sessions originating from the WAN to the LAN.
Figure 96
Stateful Inspection
The previous figure shows the P-660HWP-Dx’s default firewall rules in action as well as
demonstrates how stateful inspection works. User A can initiate a Telnet session from within
the LAN and responses to this request are allowed. However other Telnet traffic initiated from
the WAN is blocked.
10.5.1 Stateful Inspection Process
In this example, the following sequence of events occurs when a TCP packet leaves the LAN
network through the firewall's WAN interface. The TCP packet is the first in a session, and the
packet's application layer protocol is configured for a firewall rule inspection:
1
The packet travels from the firewall's LAN to the WAN.
2
The packet is evaluated against the interface's existing outbound access list, and the
packet is permitted (a denied packet would simply be dropped at this point).
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, then the settings in the
Firewall General
screen determine 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.
Содержание 802.11g HomePlug AV ADSL2+ Gateway P-660HWP-Dx
Страница 2: ......
Страница 7: ...Safety Warnings P 660HWP Dx User s Guide 39 ...
Страница 8: ...Safety Warnings P 660HWP Dx User s Guide 40 ...
Страница 10: ...Contents Overview P 660HWP Dx User s Guide 36 ...
Страница 20: ...Table of Contents P 660HWP Dx User s Guide 44 ...
Страница 32: ...List of Tables P 660HWP Dx User s Guide 40 ...
Страница 33: ...35 PART I Introduction Introducing the P 660HWP Dx 35 Introducing the Web Configurator 43 ...
Страница 34: ...36 ...
Страница 41: ...Chapter 1 Introducing the P 660HWP Dx P 660HWP Dx User s Guide 41 Figure 7 P 660HWP Dx with ISDN ...
Страница 42: ...Chapter 1 Introducing the P 660HWP Dx P 660HWP Dx User s Guide 42 ...
Страница 56: ...Chapter 2 Introducing the Web Configurator P 660HWP Dx User s Guide 48 ...
Страница 57: ...35 PART II Wizards Wizard Setup for Internet Wireless Access 59 Bandwidth Management Wizard 73 ...
Страница 58: ...36 ...
Страница 78: ...Chapter 4 Bandwidth Management Wizard P 660HWP Dx User s Guide 54 ...
Страница 80: ...36 ...
Страница 98: ...Chapter 5 WAN Setup P 660HWP Dx User s Guide 52 ...
Страница 142: ...Chapter 8 Powerline P 660HWP Dx User s Guide 42 ...
Страница 155: ...35 PART IV Security Firewalls 157 Firewall Configuration 169 Content Filtering 191 Certificates 195 ...
Страница 156: ...36 ...
Страница 176: ...Chapter 11 Firewall Configuration P 660HWP Dx User s Guide 54 Figure 99 Firewall Edit Rule ...
Страница 190: ...Chapter 11 Firewall Configuration P 660HWP Dx User s Guide 68 ...
Страница 194: ...Chapter 12 Content Filtering P 660HWP Dx User s Guide 72 ...
Страница 218: ...36 ...
Страница 222: ...Chapter 14 Static Route P 660HWP Dx User s Guide 38 ...
Страница 238: ...Chapter 16 Dynamic DNS Setup P 660HWP Dx User s Guide 38 ...
Страница 250: ...Chapter 17 Remote Management Configuration P 660HWP Dx User s Guide 46 ...
Страница 262: ...Chapter 18 Universal Plug and Play UPnP P 660HWP Dx User s Guide 58 ...
Страница 263: ...35 PART VI Maintenance and Troubleshooting System 265 Logs 271 Tools 289 Diagnostic 295 Troubleshooting 297 ...
Страница 264: ...36 ...
Страница 270: ...Chapter 19 System P 660HWP Dx User s Guide 40 ...
Страница 288: ...Chapter 20 Logs P 660HWP Dx User s Guide 52 ...
Страница 294: ...Chapter 21 Tools P 660HWP Dx User s Guide 40 ...
Страница 304: ...36 ...
Страница 340: ...Appendix C Internal SPTGEN P 660HWP Dx User s Guide 50 ...
Страница 364: ...Appendix E IP Subnetting P 660HWP Dx User s Guide 42 ...
Страница 368: ...Appendix F Command Interpreter P 660HWP Dx User s Guide 38 ...
Страница 388: ...Appendix K Legal Information P 660HWP Dx User s Guide 38 ...
Страница 394: ...Appendix L Customer Support P 660HWP Dx User s Guide 40 ...
Страница 402: ...Index P 660HWP Dx User s Guide 42 ...