User manual ZYXEL P-660H-TX V2 VERSION 3-40

[. . . ] P-660H-Tx v2 ADSL 2+ 4-port Gateway User's Guide Version 3. 40 2/2007 Edition 1 www. zyxel. com About This User's Guide About This User's Guide Intended Audience This manual is intended for people who want to configure the ZyXEL Device using the web configurator. You should have at least a basic knowledge of TCP/IP networking concepts and topology. Related Documentation · Quick Start Guide The Quick Start Guide is designed to help you get up and running right away. It contains information on setting up your network and configuring for Internet access. [. . . ] 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. P-660H-Tx v2 User's Guide 117 Chapter 8 Firewalls 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. Based on the updated state information, the inbound extended access list temporary entries might be modified, 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. 8. 5. 2 Stateful Inspection and the ZyXEL Device Additional rules may be defined to extend or override the default rules. For example, a rule may be created which 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. These custom rules work by evaluating the network traffic's Source IP address, Destination IP address, IP protocol type, and comparing these to rules set by the administrator. The ability to define firewall rules is a very powerful tool. Using custom rules, it is possible to disable all firewall protection or block all access to the Internet. Use extreme caution when creating or deleting firewall rules. Test changes after creating them to make sure they work correctly. Below is a brief technical description of how these connections are tracked. Connections may either be defined by the upper protocols (for instance, TCP), or by the ZyXEL Device itself (as with the "virtual connections" created for UDP and ICMP). 8. 5. 3 TCP Security The ZyXEL Device uses state information embedded in TCP packets. The first packet of any new connection has its SYN flag set and its ACK flag cleared; these are "initiation" packets. All packets that do not have this flag structure are called "subsequent" packets, since they represent data that occurs later in the TCP stream. If an initiation packet originates on the WAN, this means that someone is trying to make a connection from the Internet into the LAN. Except in a few special cases (see "Upper Layer Protocols" shown next), these packets are dropped and logged. 118 P-660H-Tx v2 User's Guide Chapter 8 Firewalls If an initiation packet originates on the LAN, this means that someone is trying to make a connection from the LAN to the Internet. [. . . ] Viewing Certifications 1 Go to http://www. zyxel. com. 2 Select your product on the ZyXEL home page to go to that product's page. 3 Select the certification you wish to view from this page. ZyXEL Limited Warranty ZyXEL warrants to the original end user (purchaser) that this product is free from any defects in materials or workmanship for a period of up to two years from the date of purchase. During the warranty period, and upon proof of purchase, should the product have indications of failure due to faulty workmanship and/or materials, ZyXEL will, at its discretion, repair or replace the defective products or components without charge for either parts or labor, and to whatever extent it shall deem necessary to restore the product or components to proper operating condition. [. . . ]