D-Link DWS-4026 Product Manual - Page 178

D-Link Unified Access System Software User Manual 12/10/09 The DHCP snooping application processes incoming DHCP messages. For DHCPRELEASE and DHCPDECLINE messages, the application compares the receive interface and VLAN with the client's interface and VLAN in the binding database. If the interfaces do not match, the application logs the event and drops the message. For valid client messages, DHCP snooping compares the source MAC address to the DHCP client hardware address. Where there is a mismatch, DHCP snooping logs and drops the packet. You can disable this feature using the DHCP Snooping Interface Configuration page, shown in Figure 103 below, or by using the no ip dhcp snooping verify mac-address command. DHCP snooping forwards valid client messages on trusted members within the VLAN. If DHCP relay and/or DHCP server co-exist with the DHCP snooping, the DHCP client message will be sent to the DHCP relay and/or DHCP server to process further. To access the DHCP Snooping Interface Configuration page, click LAN > L2 Features > DHCP Snooping > Interface Configuration in the navigation tree. Figure 103: DHCP Snooping Interface Configuration Field Slot/Port Trust State Logging Invalid Packets Rate Limit Burst Interval Table 88: DHCP Snooping Interface Configuration Description Select the interface for which data is to be displayed or configured. If it is enabled, the DHCP snooping application considers the port as trusted. The default is Disable. If it is enabled, the DHCP snooping application logs invalid packets on this interface. The default is Disable. Specifies the rate limit value for DHCP snooping purposes. If the incoming rate of DHCP packets exceeds the value of this object for consecutively burst interval seconds, the port will be shutdown. If this value is None, there is no limit. The default is 15 packets per second (pps). The Rate Limit range is 0 to 300. Specifies the burst interval value for rate limiting purposes on this interface. If the rate limit is None, the burst interval has no meaning and displays it as "N/A". The default is 1 second. The Burst Interval range is 1 to 15. • Click Submit to apply the new configuration and cause the change to take effect. These changes will not be retained across a power cycle unless a Save configuration is performed. DHCP SNOOPING BINDING CONFIGURATION The DHCP snooping application uses DHCP messages to build and maintain the binding database. The binding database only includes data for clients on untrusted ports. DHCP snooping creates a tentative binding from DHCP DISCOVER and Page 178 Configuring DHCP Snooping Document 34CSFP6XXUWS-SWUM100-D7