C
HAPTER
30
| General Security Measures
DHCP Snooping
– 801 –
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
u
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.
u
When enabled, DHCP messages entering an untrusted interface are
filtered based upon dynamic entries learned via DHCP snooping.
u
Table entries are only learned for trusted interfaces. Each entry
includes a MAC address, IP address, lease time, VLAN identifier, and
port identifier.
u
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.
u
Filtering rules are implemented as follows:
n
If the global DHCP snooping is disabled, all DHCP packets are
forwarded.
n
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.
n
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:
n
If the DHCP packet is a reply packet from a DHCP server
(including OFFER, ACK or NAK messages), the packet is
dropped.
Содержание DG-GS4826S
Страница 2: ...DG GS4826S DG GS4850S E012011 R01 F1 2 2 0 ...
Страница 4: ......
Страница 6: ...ABOUT THIS GUIDE 6 ...
Страница 60: ...SECTION I Getting Started 60 ...
Страница 72: ...CHAPTER 1 Introduction System Defaults 72 ...
Страница 90: ...CHAPTER 2 Initial Switch Configuration Managing System Files 90 ...
Страница 92: ...SECTION II Web Configuration 92 u Unicast Routing on page 539 u Multicast Routing on page 595 ...
Страница 137: ...CHAPTER 4 Basic Management Tasks Resetting the System 137 Figure 23 Restarting the Switch Regularly ...
Страница 138: ...CHAPTER 4 Basic Management Tasks Resetting the System 138 ...
Страница 204: ...CHAPTER 6 VLAN Configuration Configuring MAC based VLANs 204 ...
Страница 212: ...CHAPTER 7 Address Table Settings Clearing the Dynamic Address Table 212 ...
Страница 238: ...CHAPTER 9 Rate Limit Configuration 238 Figure 106 Configuring Rate Limits ...
Страница 268: ...CHAPTER 12 Quality of Service Attaching a Policy Map to a Port 268 ...
Страница 368: ...CHAPTER 14 Security Measures DHCP Snooping 368 ...
Страница 422: ...CHAPTER 15 Basic Administration Protocols Remote Monitoring 422 ...
Страница 466: ...CHAPTER 16 Multicast Filtering Multicast VLAN Registration 466 Figure 273 Showing All MVR Groups Assigned to a Port ...
Страница 487: ...CHAPTER 17 IP Configuration Setting the Switch s IP Address IP Version 6 487 Figure 285 Showing Reported MTU Values ...
Страница 488: ...CHAPTER 17 IP Configuration Setting the Switch s IP Address IP Version 6 488 ...
Страница 538: ...CHAPTER 20 IP Services Forwarding UDP Service Requests 538 ...
Страница 594: ...CHAPTER 21 Unicast Routing Configuring the Open Shortest Path First Protocol Version 2 594 ...
Страница 624: ...CHAPTER 22 Multicast Routing Configuring PIMv6 for IPv6 624 ...
Страница 638: ...CHAPTER 23 Using the Command Line Interface CLI Command Groups 638 ...
Страница 712: ...CHAPTER 26 SNMP Commands 712 ...
Страница 720: ...CHAPTER 27 Remote Monitoring Commands 720 ...
Страница 776: ...CHAPTER 29 Authentication Commands Management IP Filter 776 ...
Страница 876: ...CHAPTER 34 Port Mirroring Commands Local Port Mirroring Commands 876 ...
Страница 898: ...CHAPTER 37 Address Table Commands 898 ...
Страница 998: ...CHAPTER 41 Quality of Service Commands 998 ...
Страница 1060: ...CHAPTER 42 Multicast Filtering Commands MLD Proxy Routing 1060 ...
Страница 1078: ...CHAPTER 43 LLDP Commands 1078 ...
Страница 1088: ...CHAPTER 44 Domain Name Service Commands 1088 ...
Страница 1164: ...CHAPTER 47 IP Interface Commands IPv6 to IPv4 Tunnels 1164 ...
Страница 1260: ...CHAPTER 48 IP Routing Commands Open Shortest Path First OSPFv3 1260 ...
Страница 1304: ...SECTION IV Appendices 1304 ...
Страница 1310: ...APPENDIX A Software Specifications Management Information Bases 1310 ...
Страница 1343: ...DG GS4826S DG GS4850S E012011 R02 F1 2 2 0 ...
Страница 1344: ......