Configuring Defense Against DHCP Server DoS Attacks

CloudEngine 12800 and 12800E V200R005C10 Configuration Guide - Security

This document describes the configurations of Security, including AAA, 802.1x Authentication, ACL, TCAM ACL Customization, local attack defense, Microsegmentation, MFF, attack defense, traffic suppression and storm control, ARP security, Port security, MACsec, DHCP snooping, IPSG, URPF, SSL, Keychain and FIPS.

About This Document
AAA Configuration
- Overview of AAA
- Understanding AAA
- Application Scenarios for AAA
- Licensing Requirements and Limitations for AAA
- Summary of AAA Configuration Tasks
- Configuring Local Authentication and Authorization
- Configuring RADIUS AAA
- Configuring HWTACACS AAA
- Clearing AAA Statistics
- Configuration Examples for AAA
  - Example for Configuring RADIUS Authentication and Accounting
  - Example for Configuring HWTACACS Authentication, Accounting, and Authorization
- Troubleshooting AAA
  - An AAA Local User Cannot Be Created Due to Incorrect Password Setting
802.1x Authentication Configuration
- Understanding 802.1x Authentication
- Application Scenarios for 802.1x Authentication
- Licensing Requirements and Limitations for 802.1x Authentication
- Default Settings for 802.1x Authentication
- Configuring 802.1x Authentication
- Maintaining 802.1x Authentication
  - Clearing Statistics on 802.1x Authentication Packets
  - Forcing Users Offline
- Configuration Examples for 802.1x Authentication
  - Example for Configuring 802.1x Authentication to Control Users' Internal Access
ACL Configuration
- Overview of ACLs
- Understanding ACLs
- Application Scenarios for ACLs
- Licensing Requirements and Limitations for ACLs
- Default Settings for ACLs
- Configuring a Basic ACL
- Configuring an Advanced ACL
- Configuring a Layer 2 ACL
- Configuring a User-defined ACL
- Configuring an ARP-based ACL
- Configuring a Basic ACL6
- Configuring an Advanced ACL6
- Maintaining an ACL
  - Clearing ACL Statistics
  - Checking ACL Resource Usages
- Configuration Examples for ACLs
- ACL FAQ
  - Which Packets Cannot Be Filtered by the ACL Used by a Traffic Policy?
TCAM ACL Customization Configuration
- Overview of TCAM ACL Customization
- Licensing Requirements and Limitations for TCAM ACL Customization
- Configuring TCAM ACL Customization
  - Enabling TCAM ACL Customization
  - Configuring the TCAM ACL Customization Function for Services
- Displaying Information about a TCAM ACL Customization Profile or Preset Profile
- Configuration Examples for TCAM ACL Customization
  - Example for Configuring TCAM ACL Customization
Microsegmentation Configuration
- Overview of Microsegmentation
- Understanding Microsegmentation
- Application Scenarios for Microsegmentation
- Licensing Requirements and Limitations for Microsegmentation
- Configuring Microsegmentation
- Maintaining Microsegmentation
  - Checking Microsegmentation Statistics
  - Clearing Microsegmentation Statistics
- Configuration Examples for Microsegmentation
  - Example for Configuring IP Address-based Microsegmentation
Local Attack Defense Configuration
- Overview of Local Attack Defense
- Licensing Requirements and Limitations for Local Attack Defense
- Default Settings for Local Attack Defense
- Configuring CPU Attack Defense
- Configuring Attack Source Tracing
- Maintaining Local Attack Defense
- Configuration Examples for Local Attack Defense
  - Example for Configuring Local Attack Defense
- Troubleshooting Local Attack Defense
MFF Configuration
- Overview of MFF
- Understanding MFF
- Application Scenarios for MFF
- Licensing Requirements and Limitations for MFF
- Configuring MFF
- Configuration Examples for MFF
  - Example for Configuring MFF to Implement Layer 2 Isolation and Layer 3 Connection
- Troubleshooting MFF
  - Users Fail to Access the Internet After MFF Is Configured
Attack Defense Configuration
- Overview of Attack Defense
- Understanding Attack Defense
- Application Scenarios for Attack Defense
- Licensing Requirements and Limitations for Attack Defense
- Default Settings for Attack Defense
- Configuring Defense Against Malformed Packet Attacks
- Configuring Defense Against Packet Fragment Attacks
- Configuring Defense Against Flood Attacks
- Clearing Attack Defense Statistics
- Configuration Examples for Attack Defense
  - Example for Configuring Attack Defense
Traffic Suppression and Storm Control Configuration
- Overview of Traffic Suppression and Storm Control
- Understanding Traffic Suppression and Storm Control
  - Traffic Suppression
  - Storm Control
- Application Scenarios for Traffic Suppression and Storm Control
  - Traffic Suppression
  - Storm Control
- Licensing Requirements and Limitations for Traffic Suppression and Storm Control
- Default Settings for Traffic Suppression and Storm Control
- Configuring Traffic Suppression
- Configuring Storm Control
- Configuration Examples for Traffic Suppression and Storm Control
  - Example for Configuring Traffic Suppression
  - Example for Configuring Storm Control
ARP Security Configuration
- Overview of ARP Security
- Understanding ARP Security
- Application Scenarios for ARP Security
  - Defense Against ARP Flood Attacks
  - Defense Against ARP Spoofing Attacks
- Licensing Requirements and Limitations for ARP Security
- Default Settings for ARP Security
- Configuring Defense Against ARP Flood Attacks
- Configuring Defense Against ARP Spoofing Attacks
- Maintaining ARP Security
- Configuration Examples for ARP Security
  - Example for Configuring ARP Security Functions
  - Example for Configuring Defense Against ARP MITM Attacks
Port Security Configuration
- Overview of Port Security
- Understanding Port Security
- Application Scenarios for Port Security
- Licensing Requirements and Limitations for Port Security
- Default Settings for Port Security
- Configuring Port Security
- Configuration Examples for Port Security
  - Example for Configuring Port Security
MACsec Configuration
- Overview of MACsec
- Understanding MACsec
- Application Scenarios for MACsec
- Default Configuration
- Licensing Requirements and Limitations for MACsec
- Configuring MACsec
- Maintaining MACsec
  - Displaying MACsec Statistics
  - Clearing MACsec Statistics
- Configuration Examples for MACsec
  - Example for Configuring Point-to-Point MACsec
DHCP Snooping Configuration
- Overview of DHCP Snooping
- Understanding DHCP Snooping
  - DHCP Snooping Fundamentals
  - Option 82 Supported by DHCP Snooping
- Application Scenarios for DHCP Snooping
- Licensing Requirements and Limitations for DHCP Snooping
- Default Settings for DHCP Snooping
- Configuring Basic Functions of DHCP Snooping
- Configuring DHCP Snooping Attack Defense
- Inserting the Option 82 Field in a DHCP Message
- Maintaining DHCP Snooping
- Configuration Examples for DHCP Snooping
  - Example for Configuring DHCP Snooping Attack Defense
- Troubleshooting DHCP Snooping
  - DHCP Clients Cannot Go Online Due to DHCP Snooping
IPSG Configuration
- Overview of IPSG
- Licensing Requirements and Limitations for IPSG
- Default Settings for IPSG
- Configuring IPSG
- Maintaining IPSG
  - Checking Statistics on Discarded IP Packets
  - Clearing Statistics on Discarded IP Packets
- Configuration Examples for IPSG
  - Example for Configuring IPSG to Check Interface + IP + MAC Binding Entries
URPF Configuration
- Overview of URPF
- Understanding URPF
- Application Scenarios for URPF
- Licensing Requirements and Limitations for URPF
- Default Settings for URPF
- Configuring URPF
- Configuration Examples for URPF
  - Example for Configuring URPF (CE12800)
  - Example for Configuring URPF (CE12800E)
SSL Configuration
- Overview of SSL
- Understanding SSL
- Application Scenarios for SSL
  - Application of SSL in Information Center
- Licensing Requirements and Limitations for SSL
- Configuring SSL
  - Configuring an SSL Policy
  - Applying an SSL Policy
- Configuration Examples for SSL
  - Example for Outputting SSL-Encrypted Logs to a Log Host
Keychain Configuration
- Overview of Keychains
- Understanding Keychains
- Application Scenarios for Keychains
- Licensing Requirements and Limitations for Keychain
- Configuring a Keychain
- Configuration Examples for Keychains
  - Example for Applying the Keychain to RIP
  - Example for Applying the Keychain to BGP
FIPS Configuration
- Overview of FIPS
- Configuring the FIPS Mode
Separating the Management Port from the Service Plane
Checking Security Risks
Setting the System Master Key

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Configuring Defense Against DHCP Server DoS Attacks

Context

Malicious use of IP addresses exhausts IP addresses in the IP address pool, so authorized users cannot obtain IP addresses. The DHCP server generally identifies the MAC address of a DHCP client based on the CHADDR (client hardware address) field in the DHCP Request message. If attackers continuously apply for IP addresses by changing the CHADDR field, IP addresses in the address pool on the DHCP server may be exhausted. As a result, authorized users cannot obtain IP addresses.

To prevent DHCP users on some interfaces from applying IP addresses maliciously, you can limit the number of DHCP snooping binding entries that can be learned by an interface. When the number of DHCP snooping binding entries reaches the maximum value, no DHCP client can obtain an IP address through the interface. To prevent attackers from continuously changing the CHADDR field in the DHCP Request message, enable the device to check whether the MAC address in the Ethernet frame header matches the CHADDR field in the DHCP message. If the two values match, the message is forwarded; if the two values do not match, the message is discarded.

On a CE12800E, this function cannot be configured in the BD view.

Procedure

Run system-view
The system view is displayed.
Set the maximum number of DHCP snooping binding entries to be learned by an interface in the system, VLAN, BD view or interface view.
- In the system view:
1. Run dhcp snooping user-bind max-number max-number vlan { vlan-id1 [ to vlan-id2 ] } &<1-10>
  The maximum number of DHCP snooping binding entries is set on the device.
  
  After running this command, the value specified in this command is the total number of DHCP snooping binding entries learned by all interfaces on the device.
  
  By default, a maximum of 32768 DHCP snooping binding entries can be learned on an interface.
- In the VLAN view, BD view, or interface view:
1. Run vlan vlan-id
  The VLAN view is displayed.
  
  Or run bridge-domain bd-id
  
  The BD view is displayed.
  
  Or run interface interface-type interface-number
  
  The interface view is displayed.
2. Run dhcp snooping user-bind max-number max-number
  The maximum number of DHCP snooping binding entries is set on the interface.
  
  If you run this command in the VLAN view, the command takes effect for all the interfaces in the VLAN.
  
  By default, a maximum of 32768 DHCP snooping binding entries can be learned on an interface.
  - If you run this command in the VLAN view, the command takes effect on all the DHCP messages in the specified VLAN received by all the interfaces on the device. If you run this command in the interface view, the command takes effect on all the DHCP messages received by the specified interface. If you run this command in the BD view, the command takes effect on all the DHCP messages received in the specified BD.
  - If you run this command in the system view, VLAN view, and the interface view, the smallest value takes effect.
  - If you run this command in the system and BD views, the maximum number of users allowed to access the BD is the smaller value.
Enable the device to check the CHADDR field in the message in the system view, VLAN view, BD view or interface view.
- In the system view:
1. Run dhcp snooping check vlan { vlan-id1 [ to vlan-id2 ] } &<1-10>
  The device is enabled to check whether the MAC address in the Ethernet frame header matches the CHADDR field in the DHCP message.
  
  By default, the device does not check whether the MAC address in the Ethernet frame header matches the CHADDR field in the DHCP message.
- In the VLAN view, BD view, or interface view:
1. Run vlan vlan-id
  The VLAN view is displayed.
  
  Or run bridge-domain bd-id
  
  The BD view is displayed.
  
  Or run interface interface-type interface-number
  
  The interface view is displayed.
2. Run dhcp snooping check
  The device is enabled to check whether the MAC address in the Ethernet frame header matches the CHADDR field in the DHCP message.
  
  By default, the device does not check whether the MAC address in the Ethernet frame header matches the CHADDR field in the DHCP message.
  
  If you run the dhcp snooping check mac-address enable command in the VLAN view, the command takes effect on all the DHCP messages in the specified VLAN received by all the interfaces on the device. If you run the dhcp snooping check mac-address enable command in the interface view, the command takes effect for all the DHCP messages received on the interface. If you run this command in the BD view, the command takes effect on all the DHCP messages received in the specified BD.
3. Run quit
  Return to the system view.
(Optional) Set the alarm threshold for the number of messages discarded by DHCP snooping in the system view or interface view.
- In the system view:
1. Run dhcp snooping alarm threshold threshold
  The global alarm threshold for the number of discarded messages by DHCP snooping is set.
  
  If you run this command in the system view, the command takes effect for all the interfaces on the device.
  
  By default, the global alarm threshold for the number of messages discarded by DHCP snooping is 100.
- In the interface view:
1. Run interface interface-type interface-number
  The interface view is displayed.
2. Run dhcp snooping alarm mac-address threshold threshold
  The alarm threshold for the number of DHCP messages discarded because the CHADDR field in the DHCP messages does not match the source MAC address in the Ethernet frame header is set.
  
  By default, an alarm is generated in the system when at least 100 DHCP snooping messages are discarded, and the alarm threshold on an interface is set using the dhcp snooping alarm threshold command in the system view.
Run commit
The configuration is committed.

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Updated: 2021-09-17

Document ID: EDOC1100075347

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