User manual ZYXEL GS-4012F

[. . . ] GS-4012F/4024 Intelligent Layer 3+ Switch User's Guide Version 3. 8 4/2007 Edition 1 DEFAULT LOGIN IP Address http://192. 168. 1. 1 User Name admin Password 1234 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 ES-4124 using the web configurator or via commands. 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. [. . . ] If you want to use dynamic bindings to filter unauthorized ARP packets (typical implementation), you have to enable DHCP snooping before you enable ARP inspection. 24. 1. 1 DHCP Snooping Overview Use DHCP snooping to filter unauthorized DHCP packets on the network and to build the binding table dynamically. This can prevent clients from getting IP addresses from unauthorized DHCP servers. Untrusted Ports Every port is either a trusted port or an untrusted port for DHCP snooping. This setting is independent of the trusted/untrusted setting for ARP inspection. You can also specify the maximum number for DHCP packets that each port (trusted or untrusted) can receive each second. GS-4012F/4024 User's Guide 199 Chapter 24 IP Source Guard Trusted ports are connected to DHCP servers or other switches. The Switch discards DHCP packets from trusted ports only if the rate at which DHCP packets arrive is too high. The Switch learns dynamic bindings from trusted ports. The Switch will drop all DHCP requests if you enable DHCP snooping and there are no trusted ports. Untrusted ports are connected to subscribers. The Switch discards DHCP packets from untrusted ports in the following situations: · The packet is a DHCP server packet (for example, OFFER, ACK, or NACK). · The source MAC address and source IP address in the packet do not match any of the current bindings. · The packet is a RELEASE or DECLINE packet, and the source MAC address and source port do not match any of the current bindings. · The rate at which DHCP packets arrive is too high. 24. 1. 1. 2 DHCP Snooping Database The Switch stores the binding table in volatile memory. If the Switch restarts, it loads static bindings from permanent memory but loses the dynamic bindings, in which case the devices in the network have to send DHCP requests again. As a result, it is recommended you configure the DHCP snooping database. The DHCP snooping database maintains the dynamic bindings for DHCP snooping and ARP inspection in a file on an external TFTP server. If you set up the DHCP snooping database, the Switch can reload the dynamic bindings from the DHCP snooping database after the Switch restarts. You can configure the name and location of the file on the external TFTP server. The file has the following format: Figure 98 DHCP Snooping Database File Format <initial-checksum> TYPE DHCP-SNOOPING VERSION 1 BEGIN <binding-1> <checksum-1> <binding-2> <checksum-1-2> . . . <binding-n> <checksum-1-2-. . -n> END The <initial-checksum> helps distinguish between the bindings in the latest update and the bindings from previous updates. Each binding consists of 72 bytes, a space, and another checksum that is used to validate the binding when it is read. If the calculated checksum is not equal to the checksum in the file, that binding and all others after it are ignored. 200 GS-4012F/4024 User's Guide Chapter 24 IP Source Guard 24. 1. 1. 3 DHCP Relay Option 82 Information The Switch can add information to DHCP requests that it does not discard. This provides the DHCP server more information about the source of the requests. [. . . ] 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 446 GS-4012F/4024 User's Guide Appendix D Legal Information condition. [. . . ]