
C
HAPTER
25
| General Security Measures
DHCPv4 Snooping
– 919 –
◆
When the DHCP Snooping Information Option 82 is enabled, clients can
be identified by the switch port to which they are connected rather than
just their MAC address. DHCP client-server exchange messages are
then forwarded directly between the server and client without having to
flood them to the entire VLAN.
◆
DHCP snooping must be enabled for the DHCP Option 82 information to
be inserted into packets. When enabled, the switch will only add/
remove option 82 information in incoming DCHP packets but not relay
them. Packets are processed as follows:
■
If an incoming packet is a DHCP request packet with option 82
information, it will modify the option 82 information according to
settings specified with
ip dhcp snooping information policy
command.
■
If an incoming packet is a DHCP request packet without option 82
information, enabling the DHCP snooping information option will
add option 82 information to the packet.
■
If an incoming packet is a DHCP reply packet with option 82
information, enabling the DHCP snooping information option will
remove option 82 information from the packet.
E
XAMPLE
This example enables the DHCP Snooping Information Option.
Console(config)#ip dhcp snooping information option
Console(config)#
ip dhcp snooping
information policy
This command sets the DHCP snooping information option policy for DHCP
client packets that include Option 82 information. Use the
no
form to
restore the default setting.
S
YNTAX
ip dhcp snooping information policy
{
drop
|
keep
|
replace
}
no ip dhcp snooping information policy
drop
- Drops the client’s request packet instead of relaying it.
keep
- Retains the Option 82 information in the client request, and
forwards the packets to trusted ports.
replace
- Replaces the Option 82 information circuit-id and
remote-id fields in the client’s request with information about the
relay agent itself, inserts the relay agent’s address (when DHCP
snooping is enabled), and forwards the packets to trusted ports.
D
EFAULT
S
ETTING
replace
C
OMMAND
M
ODE
Global Configuration
Содержание ECS4110-28T
Страница 1: ...Management Guide www edge core com ECS4110 28T 28P 52T 52P 28 52 Port Gigabit Ethernet Layer 2 Switch...
Страница 2: ......
Страница 4: ......
Страница 63: ...FIGURES 63 Figure 428 Configuring VLAN Translation 1177...
Страница 64: ...FIGURES 64...
Страница 72: ...TABLES 72...
Страница 74: ...SECTION I Getting Started 74...
Страница 102: ...SECTION II Web Configuration 102 General IP Routing on page 679...
Страница 154: ...CHAPTER 4 Basic Management Tasks Resetting the System 154...
Страница 198: ...CHAPTER 5 Interface Configuration VLAN Trunking 198 Figure 65 Configuring VLAN Trunking...
Страница 272: ...CHAPTER 9 Congestion Control Automatic Traffic Control 272...
Страница 286: ...CHAPTER 10 Class of Service Layer 3 4 Priority Settings 286...
Страница 420: ...CHAPTER 13 Security Measures DHCP Snooping 420...
Страница 566: ...CHAPTER 14 Basic Administration Protocols OAM Configuration 566...
Страница 638: ...CHAPTER 15 Multicast Filtering Multicast VLAN Registration for IPv6 638...
Страница 662: ...CHAPTER 16 IP Configuration Setting the Switch s IP Address IP Version 6 662...
Страница 678: ...CHAPTER 17 IP Services Configuring the PPPoE Intermediate Agent 678...
Страница 792: ...CHAPTER 21 System Management Commands Switch Clustering 792...
Страница 822: ...CHAPTER 23 Remote Monitoring Commands 822...
Страница 888: ...CHAPTER 24 Authentication Commands PPPoE Intermediate Agent 888...
Страница 968: ...CHAPTER 25 General Security Measures Port based Traffic Segmentation 968...
Страница 994: ...CHAPTER 26 Access Control Lists ACL Information 994...
Страница 1034: ...CHAPTER 28 Link Aggregation Commands Trunk Status Display Commands 1034...
Страница 1044: ...CHAPTER 29 Power over Ethernet Commands 1044...
Страница 1084: ...CHAPTER 33 UniDirectional Link Detection Commands 1084...
Страница 1090: ...CHAPTER 34 Address Table Commands 1090...
Страница 1194: ...CHAPTER 37 VLAN Commands Configuring Voice VLANs 1194...
Страница 1388: ...CHAPTER 42 CFM Commands Delay Measure Operations 1388...
Страница 1410: ...CHAPTER 44 Domain Name Service Commands 1410...
Страница 1420: ...CHAPTER 45 DHCP Commands DHCP Relay 1420...
Страница 1472: ...CHAPTER 46 IP Routing Commands IPv4 Commands 1472...
Страница 1474: ...SECTION IV Appendices 1474...
Страница 1502: ...COMMAND LIST 1502...
Страница 1513: ......
Страница 1514: ...ECS4110 28T ECS4110 28P ECS4110 52T ECS4110 52P E072014 ST R02 150200000929A...