Free DNS, DHCP, VLANs, and VPNs practice questions
10 free 220-1201 questions on DNS, DHCP, VLANs, and VPNs, each with a full explanation — no account needed. This section sits in the Networking part of the exam. Answer every question to see your score, then read the lessons below for anything you missed.
A company has multiple VLANs and a centralized DHCP server in the server subnet. Clients in a new VLAN broadcast DHCPDISCOVER messages but never receive offers. Routing between VLANs is working for normal unicast traffic. What change is REQUIRED so clients in the new VLAN can obtain DHCP addresses?
DHCP discover traffic is broadcast-based and routers do not forward broadcasts by default. A DHCP relay agent listens on the local subnet/VLAN, adds subnet information, and forwards the request as unicast to the DHCP server, enabling DHCP across multiple subnets.
After a recent network change, users receive valid IP addresses but cannot access web resources by name. Direct connections to IP addresses work. DHCP is confirmed to be running and scopes are not exhausted. Which DHCP misconfiguration is MOST likely causing the symptom?
If clients have valid IP settings but cannot resolve names while IP-based access works, the most likely issue is incorrect DNS configuration. DHCP scope options commonly deliver DNS server addresses; misconfigured or missing DNS options cause name resolution failures.
An organization reports that outbound email is frequently rejected by recipient mail servers with errors indicating spoofing, even though users can send messages successfully. The domain has valid MX records and TLS enabled. Which missing configuration is MOST likely causing the rejections?
Receiving mail servers use SPF, DKIM, and DMARC to verify that incoming messages are authorized and not spoofed. Without these records, messages may be rejected or flagged as malicious even if SMTP delivery technically succeeds.
Which DNS record is REQUIRED for proper email delivery by telling external mail servers where to send messages for a domain?
MX (Mail Exchange) records specify which mail servers are responsible for receiving email for a domain and in what priority order they should be used.
An administrator updates a web server’s IP address but users continue reaching the old server for several hours. Which DNS mechanism BEST explains this behavior?
DNS records are cached by resolvers and clients based on their TTL. Until the TTL expires, clients may continue using the old IP address even after the authoritative record is updated.
An organization reports that users can access the company website at example.com, but www.example.com fails to load. DNS resolution for example.com is confirmed to be correct and unchanged. Which DNS record issue is MOST likely causing the problem?
The www hostname is commonly implemented as a CNAME alias pointing to the root domain. If the CNAME record is missing or incorrect, www.example.com will fail to resolve even though example.com works correctly.
An email security system verifies that messages are digitally signed and have not been altered during transmission. Which DNS-based technology provides the public key used for this verification?
DKIM uses cryptographic signatures to ensure message integrity. The receiving mail server retrieves the sender’s public key from a DNS TXT record to verify that the message was not modified in transit.
A mail administrator wants to ensure that only approved mail servers are allowed to send email on behalf of a company’s domain. Which DNS record should be configured to enforce this control?
SPF is published as a TXT record and specifies which mail servers are authorized to send email for a domain. Receiving servers use this record to detect and block spoofed or unauthorized senders.
A technician builds a new DHCP scope for a branch office. Clients receive addresses from the scope and can print to the local printer and open the local file server, but none of them can reach the internet or any headquarters server, even by IP address. Which scope option is MOST likely wrong?
The default gateway is the only setting that affects traffic leaving the local subnet, so a wrong gateway produces exactly this split: local devices work, everything beyond the router fails. A wrong subnet mask would break communication with local devices too, not just remote ones. A wrong DNS server would break name lookups but leave access by IP address working, and the stem says remote hosts fail even by IP. Lease duration controls how long an address is held, not where traffic can go.
Laptops in a training room drop off the network for a minute or two at about the same time every morning and then recover on their own. The DHCP server is up, its scope is not exhausted, and its log shows a burst of failed lease renewals just before each outage. Which DHCP condition BEST explains the pattern?
A client that cannot renew before its lease expires must give up the address and start over with a new Discover, which is exactly a brief, self-healing outage that lines up with the lease timer. Short leases make that window arrive often. Overlapping ranges would cause duplicate-address conflicts, not timed dropouts. An exclusion prevents addresses from ever being handed out, so the laptops would never have received them. Duplicate reservations are rejected by the server and would not produce a daily rhythm.
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Every lesson that covers DNS, DHCP, VLANs, and VPNs on the 220-1201 exam.