C
HAPTER
30
| General Security Measures
DHCP Snooping
– 791 –
ES-4500G Series
ip dhcp snooping
This command enables DHCP snooping globally. Use the
no
form to restore
the default setting.
S
YNTAX
[
no
]
ip dhcp snooping
D
EFAULT
S
ETTING
Disabled
C
OMMAND
M
ODE
Global Configuration
C
OMMAND
U
SAGE
◆
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
no
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.
◆
When DHCP snooping is enabled, the rate limit for the number of DHCP
messages that can be processed by the switch is 100 packets per
second. Any DHCP packets in excess of this limit are dropped.
◆
Filtering rules are implemented as follows:
■
If the global DHCP snooping is disabled, all DHCP packets are
forwarded.
■
If DHCP snooping is enabled globally, and also enabled on the VLAN
where the DHCP packet is received, all DHCP packets are forwarded
for a
trusted
port. If the received packet is a DHCP ACK message, a
dynamic DHCP snooping entry is also added to the binding table.
■
If DHCP snooping is enabled globally, and also enabled on the VLAN
where the DHCP packet is received, but the port is
not trusted
, it is
processed as follows:
■
If the DHCP packet is a reply packet from a DHCP server
(including OFFER, ACK or NAK messages), the packet is
dropped.
Summary of Contents for iPECS ES-4526G
Page 1: ...USER GUIDE User Manual ES 4550G ES 4526G Managed Layer 3 Stackable GE Switch ...
Page 38: ...CONTENTS 38 ES 4500G Series ...
Page 58: ...SECTION I Getting Started 58 ES 4500G Series ...
Page 70: ...CHAPTER 1 Introduction System Defaults 70 ES 4500G Series ...
Page 86: ...SECTION I Web Configuration 86 ES 4500G Series Multicast Filtering on page 413 ...
Page 196: ...CHAPTER 6 VLAN Configuration Configuring MAC based VLANs 196 ES 4500G Series ...
Page 204: ...CHAPTER 7 Address Table Settings Clearing the Dynamic Address Table 204 ES 4500G Series ...
Page 228: ...CHAPTER 8 Spanning Tree Algorithm Configuring Interface Settings for MSTP 228 ES 4500G Series ...
Page 230: ...CHAPTER 9 Rate Limit Configuration 230 ES 4500G Series Figure 106 Configuring Rate Limits ...
Page 260: ...CHAPTER 12 Quality of Service Attaching a Policy Map to a Port 260 ES 4500G Series ...
Page 478: ...CHAPTER 17 IP Configuration Setting the Switch s IP Address IP Version 6 478 ES 4500G Series ...
Page 528: ...CHAPTER 20 IP Services Forwarding UDP Service Requests 528 ES 4500G Series ...
Page 614: ...CHAPTER 22 Multicast Routing Configuring PIMv6 for IPv6 614 ES 4500G Series ...
Page 628: ...CHAPTER 23 Using the Command Line Interface CLI Command Groups 628 ES 4500G Series ...
Page 702: ...CHAPTER 26 SNMP Commands 702 ES 4500G Series ...
Page 710: ...CHAPTER 27 Remote Monitoring Commands 710 ES 4500G Series ...
Page 868: ...CHAPTER 34 Port Mirroring Commands Local Port Mirroring Commands 868 ES 4500G Series ...
Page 890: ...CHAPTER 37 Address Table Commands 890 ES 4500G Series ...
Page 1066: ...CHAPTER 43 LLDP Commands 1066 ES 4500G Series ...
Page 1076: ...CHAPTER 44 Domain Name Service Commands 1076 ES 4500G Series ...
Page 1286: ...CHAPTER 49 Multicast Routing Commands PIM Multicast Routing 1286 ES 4500G Series ...
Page 1288: ...SECTION I Appendices 1288 ES 4500G Series ...
Page 1294: ...APPENDIX A Software Specifications Management Information Bases 1294 ES 4500G Series ...
Page 1327: ...ES 4526G ES 4550G E042011 ST R01 150200000149A ...
Page 1328: ...APRIL 2011 ISSUE 1 0 ...