Web Management Guide-R04
Table Of Contents
- How to Use This Guide
- Contents
- Figures
- Tables
- Getting Started
- Web Configuration
- Using the Web Interface
- Basic Management Tasks
- Displaying System Information
- Displaying Hardware/Software Versions
- Configuring Support for Jumbo Frames
- Displaying Bridge Extension Capabilities
- Managing System Files
- Setting the System Clock
- Configuring the Console Port
- Configuring Telnet Settings
- Displaying CPU Utilization
- Configuring CPU Guard
- Displaying Memory Utilization
- Resetting the System
- Interface Configuration
- VLAN Configuration
- Address Table Settings
- Spanning Tree Algorithm
- Congestion Control
- Class of Service
- Layer 2 Queue Settings
- Layer 3/4 Priority Settings
- Setting Priority Processing to IP Precedence/DSCP or CoS
- Mapping Ingress DSCP Values to Internal DSCP Values
- Mapping CoS Priorities to Internal DSCP Values
- Mapping Internal DSCP Values to Egress CoS Values
- Mapping IP Precedence Values to Internal DSCP Values
- Mapping IP Port Priority to Internal DSCP Values
- Quality of Service
- VoIP Traffic Configuration
- Security Measures
- AAA Authentication, Authorization and Accounting
- Configuring User Accounts
- Web Authentication
- Network Access (MAC Address Authentication)
- Configuring HTTPS
- Configuring the Secure Shell
- Access Control Lists
- Filtering IP Addresses for Management Access
- Configuring Port Security
- Configuring 802.1X Port Authentication
- DoS Protection
- DHCPv4 Snooping
- DHCPv6 Snooping
- IPv4 Source Guard
- IPv6 Source Guard
- ARP Inspection
- Application Filter
- Basic Administration Protocols
- Configuring Event Logging
- Link Layer Discovery Protocol
- Simple Network Management Protocol
- Configuring Global Settings for SNMP
- Setting Community Access Strings
- Setting the Local Engine ID
- Specifying a Remote Engine ID
- Setting SNMPv3 Views
- Configuring SNMPv3 Groups
- Configuring Local SNMPv3 Users
- Configuring Remote SNMPv3 Users
- Specifying Trap Managers
- Creating SNMP Notification Logs
- Showing SNMP Statistics
- Remote Monitoring
- Switch Clustering
- Setting a Time Range
- Ethernet Ring Protection Switching
- OAM Configuration
- Connectivity Fault Management
- Configuring Global Settings for CFM
- Configuring Interfaces for CFM
- Configuring CFM Maintenance Domains
- Configuring CFM Maintenance Associations
- Configuring Maintenance End Points
- Configuring Remote Maintenance End Points
- Transmitting Link Trace Messages
- Transmitting Loop Back Messages
- Transmitting Delay-Measure Requests
- Displaying Local MEPs
- Displaying Details for Local MEPs
- Displaying Local MIPs
- Displaying Remote MEPs
- Displaying Details for Remote MEPs
- Displaying the Link Trace Cache
- Displaying Fault Notification Settings
- Displaying Continuity Check Errors
- OAM Configuration
- UDLD Configuration
- LBD Configuration
- Smart Pair Configuration
- Multicast Filtering
- Overview
- Layer 2 IGMP (Snooping and Query for IPv4)
- Configuring IGMP Snooping and Query Parameters
- Specifying Static Interfaces for a Multicast Router
- Assigning Interfaces to Multicast Services
- Setting IGMP Snooping Status per Interface
- Filtering IGMP Query Packets and Multicast Data
- Displaying Multicast Groups Discovered by IGMP Snooping
- Displaying IGMP Snooping Statistics
- Filtering and Throttling IGMP Groups
- MLD Snooping (Snooping and Query for IPv6)
- Multicast VLAN Registration for IPv4
- Multicast VLAN Registration for IPv6
- Basic IP Functions
- IP Configuration
- General IP Routing
- IP Services
- Appendices
- Glossary
Chapter 12
| Security Measures
DHCPv4 Snooping
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Additional considerations when the switch itself is a DHCP client – The port(s)
through which the switch submits a client request to the DHCP server must
be configured as trusted. Note that the switch will not add a dynamic entry
for itself to the binding table when it receives an ACK message from a DHCP
server. Also, when the switch sends out DHCP client packets for itself, no
filtering takes place. However, when the switch receives any messages from
a DHCP server, any packets received from untrusted ports are dropped.
DHCP Snooping Option 82
◆ 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.
◆ DHCP Snooping must be enabled for Option 82 information to be inserted into
request packets.
◆ 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.
◆ 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.
◆ 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.