C
HAPTER
14
| Security Measures
DHCP Snooping
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DHCP server, any packets received from untrusted ports are
dropped.
DHCP Snooping Option 82
u
DHCP provides a relay mechanism for sending information about its
DHCP clients or the relay agent itself to the DHCP server. Also known as
DHCP Option 82, it allows compatible DHCP servers to use the
information when assigning IP addresses, or to set other services or
policies for clients. It is also an effective tool in preventing malicious
network attacks from attached clients on DHCP services, such as IP
Spoofing, Client Identifier Spoofing, MAC Address Spoofing, and
Address Exhaustion.
u
DHCP Snooping must be enabled for Option 82 information to be
inserted into request packets.
u
When the DHCP Snooping Information Option 82 is enabled, the
requesting client (or an intermediate relay agent that has used the
information fields to describe itself) can be identified in the DHCP
request packets forwarded by the switch and in reply packets sent back
from the DHCP server. This information may specify the MAC address or
IP address of the requesting device (that is, the switch in this context).
By default, the switch also fills in the Option 82 circuit-id field with
information indicating the local interface over which the switch received
the DHCP client request, including the port and VLAN ID. This allows
DHCP client-server exchange messages to be forwarded between the
server and client without having to flood them to the entire VLAN.
u
If DHCP Snooping Information Option 82 is enabled on the switch,
information may be inserted into a DHCP request packet received over
any VLAN (depending on DHCP snooping filtering rules). The
information inserted into the relayed packets includes the circuit-id and
remote-id, as well as the gateway Internet address.
u
When the switch receives DHCP packets from clients that already
include DHCP Option 82 information, the switch can be configured to
set the action policy for these packets. The switch can either drop the
DHCP packets, keep the existing information, or replace it with the
switch’s relay information.
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: ......