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Dynamic ARP Inspection (DAI) is a critical security feature that prevents ARP spoofing attacks by validating ARP packets in a network. It ensures that only legitimate ARP requests and replies are forwarded, blocking malicious attempts to corrupt the ARP cache.
How DAI Works
1. ARP Cache: Stores IP-to-MAC address mappings.
2. DAI-Enabled Ports: Inspect ARP traffic for validity.
- Attacker Scenario: A rogue device (e.g., MAC
CC:CC:CC) sends fake ARP replies. - DAI Protection: Blocks and shuts down the malicious port (e.g., Port 3).
You Should Know: Practical Implementation of DAI
Cisco IOS Configuration
Enable DAI on a switch to protect against ARP spoofing:
Switch(config) ip arp inspection vlan 10 Switch(config) interface gigabitethernet 1/0/1 Switch(config-if) ip arp inspection trust
– Verify DAI Status:
Switch show ip arp inspection vlan 10
– Check Violations:
Switch show ip arp inspection statistics
Linux ARP Security (ARPWatch)
Monitor ARP changes on Linux:
sudo apt install arpwatch sudo systemctl start arpwatch
– View ARP Logs:
sudo tail -f /var/log/arpwatch.log
Windows ARP Commands
Check ARP table:
arp -a
Clear ARP cache:
netsh interface ip delete arpcache
Preventative Measures
- Use static ARP entries for critical servers:
arp -s 192.168.1.1 00:11:22:33:44:55
- Enable Port Security on switches:
Switch(config-if) switchport port-security Switch(config-if) switchport port-security maximum 1
What Undercode Say
DAI is a powerful tool against ARP poisoning, but it must be combined with other security measures like port security, VLAN segmentation, and regular monitoring. Always verify ARP tables and log suspicious activity.
Expected Output:
- A secure network with validated ARP traffic.
- Blocked ARP spoofing attempts.
- Logged violations for further analysis.
For deeper learning, check Cisco’s official docs:
References:
Reported By: Nasir Amin – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
