Does DHCP Snooping Let It Through?

About this interactive

From the lesson's rules: 1. **Trusted port:** forward. 2. **Untrusted port, server message** (Offer, Ack): drop. That stops rogue DHCP servers, malicious or accidental. 3. **Untrusted port, client message:** check the rate limit, if one is set. 4. **Discover or Request:** the chaddr field inside must match the frame's source MAC. 5. **Release or Decline:** must match the DHCP snooping binding table, so nobody can release another client's lease. Turning snooping on makes every port untrusted; trust only the ports toward real DHCP servers. The binding table it builds (IP, MAC, port) is used again by dynamic ARP inspection and IP source guard.

What you'll learn

Predict whether DHCP snooping forwards or drops a DHCP message: server messages only on trusted ports, client messages checked for rate, chaddr and, for Release and Decline, the binding table
Explain how these checks stop DHCP spoofing (a rogue server) and DHCP starvation

Aligned to

Cisco CCNA

5.7 Configure and verify Layer 2 security features

Key terms

DHCP Snooping: A switch security feature that classifies ports as trusted (connected to legitimate DHCP servers) or untrusted (connected to end devices) and drops DHCP server responses received on untrusted ports. It builds a binding database of valid IP-to-MAC-to-port mappings used by other Layer 2 security features like Dynamic ARP Inspection.
DHCP Snooping Binding Table: A database maintained by a switch that records MAC address, IP address, lease time, VLAN, and interface mappings learned from validated DHCP exchanges.
DHCP Spoofing: An attack technique in which a threat actor emulates a legitimate DHCP server to intercept and respond to client requests, enabling denial-of-service or adversary-in-the-middle attacks.
DHCP Starvation: An attack in which an attacker exhausts all available IP addresses in a DHCP pool by sending excessive requests, preventing legitimate devices from obtaining network configuration.

Topics

Dhcp Snooping Dhcp Spoofing Dhcp Starvation Layer 2 Security Interactive Streak Sort

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