iii
Application environment ······································································································································· 56
Fundamentals ························································································································································· 56
DHCP relay agent support for Option 82 ·········································································································· 57
DHCP relay agent configuration task list ····················································································································· 58
Enabling DHCP ······························································································································································ 58
Enabling the DHCP relay agent on an interface ········································································································ 58
Correlating a DHCP server group with a relay agent interface················································································ 59
Configuration guidelines ······································································································································ 59
Configuration procedure ······································································································································ 59
Configuring the DHCP relay agent security functions ································································································ 60
Configuring address check ·································································································································· 60
Configuring periodic refresh of dynamic client entries ····················································································· 61
Configuring the DHCP relay agent to support authorized ARP ········································································ 61
Enabling unauthorized DHCP server detection ·································································································· 62
Enabling DHCP starvation attack protection ······································································································ 62
Enabling client offline detection ··································································································································· 63
Configuring the DHCP relay agent to release an IP address ···················································································· 64
Configuring the DHCP relay agent to support Option 82 ························································································· 64
Configuration prerequisites ·································································································································· 64
Configuration guidelines ······································································································································ 64
Configuration procedure ······································································································································ 65
Displaying and maintaining the DHCP relay agent ··································································································· 65
DHCP relay agent configuration examples ················································································································· 66
DHCP relay agent configuration example ·········································································································· 66
DHCP relay agent Option 82 support configuration example ········································································· 68
Troubleshooting DHCP relay agent configuration ······································································································ 68
Symptom ································································································································································· 68
Analysis ·································································································································································· 68
Solution ··································································································································································· 69
Configuring DHCP client ··········································································································································· 70
Enabling the DHCP client on an interface ··················································································································· 70
Configuration guidelines ······································································································································ 70
Configuration procedure ······································································································································ 70
Displaying and maintaining the DHCP client ·············································································································· 71
DHCP client configuration example ····························································································································· 71
Network requirements ··········································································································································· 71
Configuration procedure ······································································································································ 72
Verifying the configuration ··································································································································· 72
Configuring DHCP snooping ····································································································································· 74
Overview ········································································································································································· 74
DHCP snooping functions ····································································································································· 74
Application environment of trusted ports ············································································································ 75
DHCP snooping support for Option 82 ·············································································································· 76
Configuring DHCP snooping basic functions ·············································································································· 77
Configuration guidelines ······································································································································ 77
Configuration procedure ······································································································································ 77
Configuring DHCP snooping to support Option 82 ··································································································· 78
Configuration guidelines ······································································································································ 78
Configuration procedure ······································································································································ 78
Configuring DHCP snooping entries backup ·············································································································· 80
Enabling DHCP starvation attack protection ··············································································································· 81
Enabling DHCP-request message attack protection ···································································································· 81
Displaying and maintaining DHCP snooping ············································································································· 82
