ZyXEL Communications P-873HNU-51B, Руководство пользователя

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P-873HNU(P)-51B User’s Guide
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Firewall
15.1 Overview
This chapter shows you how to enable and configure the VDSL Router firewall. Use the firewall to
protect your VDSL Router and network from attacks by hackers on the Internet and control access
to it. By default the firewall:
• allows traffic that originates from your LAN computers to go to all other networks.
• blocks traffic that originates on other networks from going to the LAN.
The following figure illustrates the default firewall action. User A can initiate an IM (Instant
Messaging) session from the LAN to the WAN (1). Return traffic for this session is also allowed (2).
However other traffic initiated from the WAN is blocked (3 and 4).
Figure 89
Default Firewall Action
15.1.1 What You Can Do in this Chapter
• Use the Firewall screen to configure the security level of the firewall on the VDSL Router
( Section 15.2 on page 191 ).
• Use the Protocol screen to add or remove predefined Internet services and configure firewall
rules ( Section 15.3 on page 191 ).
• Use the Access Control screen to view and configure incoming/outgoing filtering rules ( Section
15.4 on page 193 ).
15.1.2 What You Need to Know
SYN Attack
A SYN attack floods a targeted system with a series of SYN packets. Each packet causes the
targeted system to issue a SYN-ACK response. While the targeted system waits for the ACK that
WAN
LAN
3
4
1
2
A