mediumMultiple Select
DHCP Snooping Security Features
Which three statements about DHCP snooping are true? (Choose three.)
Quick Answer
The answer is that ports connected to DHCP servers should be configured as trusted ports. This is correct because DHCP snooping operates by dividing switch ports into trusted and untrusted categories; trusted ports are allowed to send DHCP server messages (like OFFER and ACK), while untrusted ports, typically facing clients, have these messages filtered out to prevent rogue DHCP server attacks. On the ENCOR 350-401 exam, this concept tests your understanding of Layer 2 security mechanisms, often appearing in multiple-choice questions where you must identify true statements about DHCP snooping features. A common trap is confusing the storage location of the binding database—it is kept in flash memory, not NVRAM—or assuming DHCP snooping applies to DHCPv6 by default, which it does not. Remember the memory tip: "Trust the server, distrust the client" to quickly recall that trusted ports face upstream DHCP servers.
⚠ Common exam trap
The trap is assuming the binding database is persistent by default (it is not) and assuming DHCP snooping covers DHCPv6 automatically (it does not; DHCPv6 snooping is a separate feature).
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
DHCP snooping is configured on Layer 2 switches to filter DHCP messages on untrusted ports.
Option A is correct because DHCP snooping is a Layer 2 switch security feature that inspects DHCP messages and filters them on untrusted ports, blocking unauthorized DHCP server replies such as rogue offers. Option B is correct because the DHCP snooping binding table records the client MAC address, leased IP address, lease time, VLAN, and ingress port, which is exactly the information used for subsequent IP-to-MAC enforcement. Option C is correct because ports facing legitimate DHCP servers (or uplinks toward them) must be configured as trusted so their DHCP OFFER/ACK messages are not dropped, while host-facing ports remain untrusted. Option D is not correct because the binding database is held in memory and is not stored in NVRAM by default; persistence requires explicit configuration such as a database agent or file. Option E is not correct because DHCP snooping is an IPv4 DHCP feature, and DHCPv6 snooping/guard must be enabled separately rather than being validated by default when DHCP snooping is enabled globally.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
DHCP snooping is configured on Layer 2 switches to filter DHCP messages on untrusted ports.
Why this is correct
DHCP snooping operates at Layer 2, intercepting DHCP messages arriving on untrusted ports and dropping server-sourced offers, ACKs and NAKs that would otherwise reach clients. Configuring it on access switches satisfies the stem's requirement to filter rogue DHCP traffic before it crosses the broadcast domain, which a Layer 3 device could not do at frame level.
- ✓
The DHCP snooping binding table includes the client MAC address, IP address, lease time, VLAN, and port number.
Why this is correct
Each binding table entry maps a client MAC address to its leased IP address, lease time, VLAN and ingress port, providing the Layer 2 to Layer 3 association that DAI and IP Source Guard later reference.
- ✓
Ports connected to DHCP servers should be configured as trusted ports.
Why this is correct
DHCP snooping drops server-sourced DHCP messages arriving on untrusted ports. Because legitimate DHCP OFFERs and ACKs originate from the server, the port facing the server must be trusted so those replies are not discarded, allowing clients to obtain leases.
- ✗
The DHCP snooping binding database is stored in NVRAM by default.
Why it's wrong here
The DHCP snooping binding database is held in memory and lost on reload; it is not stored in NVRAM by default. It tempts because NVRAM persists other switch configuration, but bindings are dynamic entries, so persistence requires the database agent writing to flash or a URL.
- ✗
DHCP snooping validates DHCPv6 messages by default when enabled globally.
Why it's wrong here
DHCP snooping operates on DHCPv4; it does not validate DHCPv6 messages by default, and IPv6 snooping is configured separately via IPv6 DHCP guard. It tempts because snooping filters DHCP traffic generally, but the feature's default scope is IPv4 only.
Visual reference
Quick reference
Access Control Model Comparison
| Model | Acronym | Who Controls Access? | Best For |
|---|---|---|---|
| Discretionary Access Control | DAC | Resource owner | Small teams, file shares |
| Mandatory Access Control | MAC | System / security labels | Classified govt / military |
| Role-Based Access Control | RBAC | Administrator (via roles) | Enterprise environments |
| Attribute-Based Access Control | ABAC | Policy engine (user + resource attributes) | Fine-grained, dynamic policies |
| Rule-Based Access Control | RuBAC | System rules / ACLs | Firewall rules, network ACLs |
Go deeper
Related to this question
Learn chapter
Wireless Deployment Models and Security
Key term
L2 Security Features
L2 Security Features are network security mechanisms that operate at Layer 2 of the OSI model to protect local network traffic from threats like MAC spoofing, ARP attacks, and unauthorized access.
Key term
DHCP snooping
DHCP snooping is a network security feature that filters untrusted DHCP messages to prevent rogue DHCP servers from giving out false IP addresses.
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Same concept, more angles
1 more way this is tested on 350-401
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. Which three statements about DHCP snooping are true? (Choose three.)
hard- ✓ A.DHCP snooping is configured on a per-VLAN basis.
- B.DHCP snooping prevents all types of ARP spoofing attacks.
- ✓ C.The DHCP snooping binding database includes the client MAC address, IP address, lease time, VLAN, and port.
- ✓ D.Ports connected to DHCP servers should be configured as trusted ports.
- E.DHCP snooping encrypts all DHCP traffic between the client and server.
Why A: Option A is correct because DHCP snooping is enabled globally and then applied on a per-VLAN basis using commands such as 'ip dhcp snooping' and 'ip dhcp snooping vlan <vlan-id>', so its filtering behavior is scoped to specific VLANs. Option C is correct because the DHCP snooping binding table records entries containing the client MAC address, leased IP address, lease time, VLAN, and ingress interface/port, which is exactly the data used later by features like Dynamic ARP Inspection and IP Source Guard. Option D is correct because switch ports facing legitimate DHCP servers must be configured as trusted with 'ip dhcp snooping trust'; otherwise the snooping feature drops server-originated DHCP OFFER/ACK messages arriving on untrusted ports. Option B is not correct because DHCP snooping itself does not stop all ARP spoofing; it only builds a binding table, and ARP spoofing mitigation requires Dynamic ARP Inspection to use that table. Option E is not correct because DHCP snooping is a Layer 2 filtering and binding-table mechanism, not an encryption protocol, so it does not encrypt DHCP traffic between clients and servers.
JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Cisco exam blueprint
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