Dell Force10 E600i FTOS Version 8.4.1.5 Configuration Guide for ExaScale - Page 317

To view the ip helper-address configuration for an interface, use the command show ip interface from EXEC privilege mode. R1_E600#show ip int gig 1/3 GigabitEthernet 1/3 is up, line protocol is down Internet address is 10.11.0.1/24 Broadcast address is 10.11.0.255 Address determined by user input IP MTU is 1500 bytes Helper address is 192.168.0.1 192.168.0.2 Directed broadcast forwarding is disabled Proxy ARP is enabled Split Horizon is enabled Poison Reverse is disabled ICMP redirects are not sent ICMP unreachables are not sent Configure Secure DHCP c e s This feature is available on the following platforms: DHCP as defined by RFC 2131 provides no authentication or security mechanisms. Secure DHCP is a suite of features that protects networks that use dynamic address allocation from spoofing and attacks. • Option 82 • DHCP Snooping • Dynamic ARP Inspection • Source Address Validation Option 82 RFC 3046 (Relay Agent Information option, or Option 82) is used for class-based IP address assignment. The code for the Relay Agent Information option is 82, and is comprised of two sub-options, Circuit ID and Remote ID. • Circuit ID is the interface on which the client-originated message is received. • Remote ID identifies the host from which the message is received. The value of this sub-option is the MAC address of the relay agent that adds Option 82. The DHCP relay agent inserts Option 82 before forwarding DHCP packets to the server. The server can use this information to: • track the number of address requests per relay agent; restricting the number of addresses available per relay agent can harden a server against address exhaustion attacks. • associate client MAC addresses with a relay agent to prevent offering an IP address to a client spoofing the same MAC address on a different relay agent. Dynamic Host Configuration Protocol | 317