iv
Restrictions and guidelines: DHCP snooping configuration ······························································· 86
DHCP snooping tasks at a glance ······························································································· 86
Configuring basic DHCP snooping features ··················································································· 86
Configuring basic DHCP snooping features in a common network ··············································· 86
Configuring DHCP snooping support for Option 82 ·········································································· 88
Configuring DHCP snooping entry auto backup ·············································································· 89
Setting the maximum number of DHCP snooping entries ·································································· 89
Configuring DHCP packet rate limit ······························································································ 90
Configuring DHCP snooping security features ················································································ 90
Enabling DHCP starvation attack protection ············································································ 90
Enabling DHCP-REQUEST attack protection ·········································································· 91
Configuring a DHCP packet blocking port ··············································································· 91
Enabling DHCP snooping logging ································································································ 92
Disabling DHCP snooping on an interface ····················································································· 92
Display and maintenance commands for DHCP snooping ································································· 93
DHCP snooping configuration examples ······················································································· 93
Example: Configuring basic DHCP snooping features globally ···················································· 93
Example: Configuring basic DHCP snooping features for a VLAN ················································ 94
Example: Configuring DHCP snooping support for Option 82 ······················································ 95
Configuring the BOOTP client ··························································· 97
About BOOTP client ················································································································· 97
BOOTP client application ···································································································· 97
Obtaining an IP address dynamically ····················································································· 97
Protocols and standards ····································································································· 97
Configuring an interface to use BOOTP for IP address acquisition ······················································ 97
Display and maintenance commands for BOOTP client ···································································· 98
BOOTP client configuration examples ·························································································· 98
Example: Configuring BOOTP client ······················································································ 98
Configuring DNS ············································································ 99
About DNS ····························································································································· 99
Types of DNS services ······································································································· 99
Static domain name resolution ····························································································· 99
Dynamic domain name resolution ························································································· 99
DNS proxy ····················································································································· 100
DNS spoofing ················································································································· 101
DNS tasks at a glance············································································································· 102
Configuring the DNS client ······································································································· 102
Configuring static domain name resolution ············································································ 102
Configuring dynamic domain name resolution ········································································ 103
Configuring the DNS proxy ······································································································· 104
Configuring DNS spoofing ········································································································ 104
Specifying the source interface for DNS packets ··········································································· 105
Configuring the DNS trusted interface ························································································ 105
Setting the DSCP value for outgoing DNS packets ········································································ 106
Display and maintenance commands for DNS ·············································································· 106
IPv4 DNS configuration examples ····························································································· 106
Example: Configuring static domain name resolution ······························································ 106
Example: Configuring dynamic domain name resolution ·························································· 107
Example: Configuring DNS proxy ························································································ 109
IPv6 DNS configuration examples ····························································································· 111
Example: Configuring static domain name resolution ······························································ 111
Example: Configuring dynamic domain name resolution ·························································· 111
Example: Configuring DNS proxy ························································································ 114
Troubleshooting DNS configuration ···························································································· 115
Failure to resolve IPv4 addresses ······················································································· 115
Failure to resolve IPv6 addresses ······················································································· 116
Configuring IP forwarding basic settings ············································ 117
About FIB table ····················································································································· 117
Saving the IP forwarding entries to a file ····················································································· 117
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