Netgear XCM8806 Chassis User Manual - Page 451
DHCP Request, DHCP Reply, Security, NETGEAR 8800 User Manual
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NETGEAR 8800 User Manual configure ip-security dhcp-snooping information option Note: When DHCP relay is configured in a DHCP snooping environment, the relay agent IP address should be configured as the trusted server. When DHCP option 82 is enabled, two types of packets need to be handled: • DHCP Request: When the switch (relay agent) receives a DHCP request, option 82 is added at the end of the packet. If the option has already been enabled, then the action taken depends on the configured policy (drop packet, keep existing option 82 value, or replace the existing option). Unless configured otherwise using the configure ip-security dhcp-snooping information circuit-id vlan-information, the vlan_info portion of the circuit ID added will be the VLAN ID of the ingress VLAN. • DHCP Reply: When the option 82 information check is enabled, the packets received from the DHCP server are checked for option 82 information. If the remote ID sub-option is the switch's MAC address, the packet is sent to the client; if not, the packet is dropped. If the check is not enabled. the packets are forwarded as-is. To disable the DHCP relay agent option, use the following command: unconfigure ip-security dhcp-snooping information option In some instances, a DHCP server may not properly handle a DHCP request packet containing a relay agent option. To prevent DHCP reply packets with invalid or missing relay agent options from being forwarded to the client, use the following command: configure ip-security dhcp-snooping information check To disable checking of DHCP replies, use this command: unconfigure ip-security dhcp-snooping information check A DHCP relay agent may receive a client DHCP packet that has been forwarded from another relay agent. If this relayed packet already contains a relay agent option, then the switch will handle this packet according to the configured DHCP relay agent option policy. The possible actions are to replace the option information, to keep the information, or to drop packets containing option 82 information. To configure this policy, use the following command: configure ip-security dhcp-snooping information policy The default relay policy is replace. To configure the policy to the default, use this command: unconfigure ip-security dhcp-snooping information policy The Layer 2 relay agent option allows you to configure the circuit ID on a VLAN or port basis., the Circuit-ID can contain a variable length (up to 32 bytes long) ASCII string with the following format: - Chapter 17. Security | 451
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