D-Link DXS-3400 Emulator - Page 311
ip dhcp snooping limit entries
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DXS-3400 Series Lite Layer 3 Stackable 10GbE Managed Switch CLI Reference Guide When a port is configured as a untrusted interface, the DHCP message arrives at the port on a VLAN that is enabled for DHCP snooping. The switch forwards the DHCP packet unless any of the following conditions occur (in which case the packet is dropped): • The switch port receives a packet (such as a DHCPOFFER, DHCPACK, DHCPNAK, or DHCPLEASEQUERY packet) from a DHCP server outside the firewall. • If the ip dhcp snooping verify mac-address command is enabled, the source MAC in the Ethernet header must be the same as the DHCP client hardware address to pass the validation. • The untrusted interface receives a DHCP packet that includes a relay agent IP address that is not 0.0.0.0 or the relay agent forward a packet that includes Option 82 to an untrusted interface. • The router receives a DHCPRELEASE or DHCPDECLINE message from an untrusted host with an entry in the DHCP snooping binding table, and the interface information in the binding table does not match the interface on which the message was received. In addition to doing the validation, DHCP snooping also create a binding entry based on the IP address assigned to client by the server in DHCP snooping binding database. The binding entry contains information including MAC address, IP address, the VLAN ID and port ID where the client is located, and the expiry of the lease time. Example This example shows how to enable DHCP snooping trust for port 1/0/3. Switch# configure terminal Switch(config)# interface ethernet 1/0/3 Switch(config-if)# ip dhcp snooping trust Switch(config-if)# 24-9 ip dhcp snooping limit entries This command is used to configure the number of the DHCP snooping binding entries that an interface can learn. Use the no form of this command to reset the DHCP message entry limit. ip dhcp snooping limit entries {NUMBER | no-limit} no ip dhcp snooping limit entries Parameters NUMBER no-limit Specifies the number of DHCP snooping binding entries limited on a port. The range of value is from 0 to 1024. Specifies no binding entry number limitation. Default By default, this option is no-limit. Command Mode Interface Configuration Mode. Command Default Level Level: 12. Usage Guideline This command is available for physical port and port-channel interface configuration. This command only takes effect on untrusted interfaces. The system will stop learning binding entries associated with the port if the maximums number is exceeded. 307
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