
Chapter 9
| General Security Measures
DHCPv4 Snooping
– 306 –
ip dhcp snooping
This command enables DHCP snooping globally. Use the
no
form to restore the
default setting.
Syntax
[
no
]
ip dhcp snooping
Default Setting
Disabled
Command Mode
Global Configuration
Command Usage
◆
Network traffic may be disrupted when malicious DHCP messages are received
from an outside source. DHCP snooping is used to filter DHCP messages
received on an unsecure interface from outside the network or fire wall. When
DHCP snooping is enabled globally by this command, and enabled on a VLAN
interface by the
command, DHCP messages received on
an untrusted interface (as specified by the
command) from a device not listed in the DHCP snooping table will be
dropped.
◆
When enabled, DHCP messages entering an untrusted interface are filtered
based upon dynamic entries learned via DHCP snooping.
◆
Table entries are only learned for trusted interfaces. Each entry includes a MAC
address, IP address, lease time, VLAN identifier, and port identifier.
ip dhcp snooping information
option circuit-id
Enables or disables the use of DHCP Option 82
information circuit-id suboption
IC
configures the maximum number of DHCP clients which
can be supported per interface
IC
Configures the specified interface as trusted
IC
clear ip dhcp snooping
binding
Clears DHCP snooping binding table entries from RAM
PE
clear ip dhcp snooping
database flash
Removes all dynamically learned snooping entries from
flash memory.
PE
ip dhcp snooping database
flash
Writes all dynamically learned snooping entries to flash
memory
PE
Shows the DHCP snooping configuration settings
PE
Shows the DHCP snooping binding table entries
PE
Table 58: DHCP Snooping Commands
(Continued)
Command
Function
Mode
Summary of Contents for ECS4120-28F
Page 36: ...Contents 36...
Page 38: ...Figures 38...
Page 46: ...Section I Getting Started 46...
Page 70: ...Chapter 1 Initial Switch Configuration Setting the System Clock 70...
Page 86: ...Chapter 2 Using the Command Line Interface CLI Command Groups 86...
Page 202: ...Chapter 5 SNMP Commands Additional Trap Commands 202...
Page 210: ...Chapter 6 Remote Monitoring Commands 210...
Page 216: ...Chapter 7 Flow Sampling Commands 216...
Page 278: ...Chapter 8 Authentication Commands PPPoE Intermediate Agent 278...
Page 360: ...Chapter 9 General Security Measures Port based Traffic Segmentation 360...
Page 384: ...Chapter 10 Access Control Lists ACL Information 384...
Page 424: ...Chapter 11 Interface Commands Power Savings 424...
Page 446: ...Chapter 13 Power over Ethernet Commands 446...
Page 456: ...Chapter 14 Port Mirroring Commands RSPAN Mirroring Commands 456...
Page 488: ...Chapter 17 UniDirectional Link Detection Commands 488...
Page 494: ...Chapter 18 Address Table Commands 494...
Page 554: ...Chapter 20 ERPS Commands 554...
Page 620: ...Chapter 22 Class of Service Commands Priority Commands Layer 3 and 4 620...
Page 638: ...Chapter 23 Quality of Service Commands 638...
Page 772: ...Chapter 25 LLDP Commands 772...
Page 814: ...Chapter 26 CFM Commands Delay Measure Operations 814...
Page 836: ...Chapter 28 Domain Name Service Commands 836...
Page 848: ...Chapter 29 DHCP Commands DHCP Relay Option 82 848...
Page 902: ...Section III Appendices 902...
Page 916: ...Glossary 916...
Page 926: ...CLI Commands 926...
Page 937: ......
Page 938: ...E092017 CS R02...