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What does reverse DNS (rDNS) lookup do in networking?
a. Converts a domain name to an IP address
b. Converts an IP address to a domain name
c. Finds the MAC address associated with an IP
d. Authenticates DHCP traffic
Answer: b. Converts an IP address to a domain namegeeksforgeeks+2
Which DNS record type is used for reverse lookup?
a. A record
b. TXT record
c. PTR record
d. MX record
Answer: c. PTR recordfalconcloud+2
In IPv4, what special domain is used for reverse DNS lookups?
a. in-addr.arpa
b. ip6.arpa
c. com.arpa
d. reverse.arpa
Answer: a. in-addr.arpalearn.microsoft+2
What is the primary use of reverse DNS in email servers?
a. Blocking malware
b. Verifying sender legitimacy
c. Encrypting messages
d. Routing emails
Answer: b. Verifying sender legitimacyblogs.manageengine+1
Which order is the IP address written for a reverse DNS query?
a. As originally assigned
b. Reverse order (least to most significant)
c. Randomized arrangement
d. Hex format
Answer: b. Reverse order (least to most significant)ripe+2
What is required for a successful reverse DNS lookup?
a. A properly configured PTR record
b. An MX record
c. An SPF entry
d. A TXT record
Answer: a. A properly configured PTR recordbigrock+2
Where are PTR records stored in IPv4 reverse lookups?
a. com domain
b. in-addr.arpa domain
c. root zone
d. anycast domain
Answer: b. in-addr.arpa domaingeeksforgeeks+2
What command is commonly used on Linux for reverse DNS lookup?
a. ping
b. dig -x [ip_address]
c. traceroute
d. whois
Answer: b. dig -x [ip_address]phoenixnap
On Windows, which command performs a reverse DNS lookup?
a. arp -a
b. nslookup [ip_address]
c. tracert
d. ipconfig /displaydns
Answer: b. nslookup [ip_address]phoenixnap
What does a failed reverse DNS lookup indicate?
a. IP address is unreachable
b. No PTR record exists for the IP address
c. DNS server is down
d. The host is powered off
Answer: b. No PTR record exists for the IP addressbigrock+1
What record type would map 192.168.1.26 to its hostname in a reverse zone?
a. PTR record
b. A record
c. AAAA record
d. CNAME record
Answer: a. PTR recordripe+1
Which reverse DNS lookup zone format is used for an IPv4 block 192.168.1.0/24?
a. 1.168.192.in-addr.arpa
b. 192.168.1.24.in-addr.arpa
c. 168.192.1.in-addr.arpa
d. 24.1.168.192.in-addr.arpa
Answer: a. 1.168.192.in-addr.arpablogs.manageengine
What is the purpose of using reverse DNS in logging and monitoring?
a. Hides sensitive IPs
b. Transforms raw IP addresses into readable domain names
c. Encrypts logs
d. Compresses data
Answer: b. Transforms raw IP addresses into readable domain namesgeeksforgeeks+1
Reverse DNS lookups help in which of the following security tasks?
a. Virus scanning
b. Identifying incoming hostnames for connections
c. Bandwidth management
d. Firewall configuration
Answer: b. Identifying incoming hostnames for connectionsblogs.manageengine
What happens if multiple domains share the same IP with proper PTR records?
a. Reverse lookup will list all domains
b. Only one domain is returned per PTR record
c. All domains are ignored
d. The query fails
Answer: b. Only one domain is returned per PTR recordhackertarget
What is a common use of reverse DNS in public web hosting?
a. To determine the number of sites sharing the host
b. To block ads
c. To renew certificates
d. To configure proxies
Answer: a. To determine the number of sites sharing the hosthackertarget
Which DNS zone must be configured for reverse lookups?
a. Forward zone
b. Reverse zone
c. Proxy zone
d. Mail zone
Answer: b. Reverse zoneripe+1
In which scenario might a reverse DNS lookup be critical for compliance?
a. Auditing network access by hostname
b. Blocking DNS tunneling
c. Disabling guest Wi-Fi
d. Assigning static IPs
Answer: a. Auditing network access by hostnamearin+1
What is the primary difference between A record and PTR record?
a. A record maps domain to IP, PTR maps IP to domain
b. PTR records are encrypted, A records are plain text
c. PTR records map to MAC address, A records to hostname
d. PTR records resolve only IPv6
Answer: a. A record maps domain to IP, PTR maps IP to domainfalconcloud+1
Which protocol uses reverse DNS lookup for spam filtering?
a. FTP
b. SMTP
c. SNMP
d. SSH
Answer: b. SMTPgeeksforgeeks+1
Which record is searched when doing a reverse DNS lookup for IPv6 addresses?
a. PTR record in ip6.arpa
b. A record in in-addr.arpa
c. MX record in root zone
d. AAAA record
Answer: a. PTR record in ip6.arpafalconcloud+2
What might a firewall log show after reverse DNS is enabled?
a. MAC addresses
b. Hostnames instead of IPs
c. NAT translations
d. Service ports
Answer: b. Hostnames instead of IPsblogs.manageengine+1
Which field in a PTR record specifies the hostname?
a. Class
b. rdata
c. TTL
d. Type
Answer: b. rdatadnschecker+1
Why is in-addr.arpa significant in reverse DNS?
a. It serves as the namespace for IPv4 reverse lookups
b. It is used for email routing
c. It stores MX records
d. It configures web proxies
Answer: a. It serves as the namespace for IPv4 reverse lookupslearn.microsoft+2
Which tool is commonly used for reverse lookup validation online?
a. Reverse IP Lookup (MxToolBox)
b. Traceroute
c. Netstat
d. Ifconfig
Answer: a. Reverse IP Lookup (MxToolBox)mxtoolbox
What does PTR RR stand for in DNS terminology?
a. Pointer resource record
b. Primary record
c. Proxy transfer record
d. Packet router record
Answer: a. Pointer resource recordlearn.microsoft+1
What reverse DNS zone would you configure for IPv6 addresses?
a. ip6.arpa
b. arpa6.in
c. ipv6.addr.arpa
d. ipv6.zone.arpa
Answer: a. ip6.arpafalconcloud+2
What can happen to mail delivery if a sender’s IP lacks a correct PTR record?
a. Delivery is delayed
b. Mail is rejected or marked as spam
c. Email gets encrypted
d. Message returns to sender
Answer: b. Mail is rejected or marked as spammailmodo+2
Which statement best describes a PTR record’s structure?
a. <name> <ttl> <class> <type> <rdata>
b. <ip> <domain> <priority> <type> <flags>
c. <domain> <mx> <ip> <ttl>
d. <hostname> <alias> <ip> <zone>
Answer: a. <name> <ttl> <class> <type> <rdata>whatsmydns+1
Why are reverse DNS lookups important in shared hosting environments?
a. To identify reputation issues with neighboring sites
b. To block database access
c. To generate unique SSL certificates
d. To add bandwidth
Answer: a. To identify reputation issues with neighboring siteshackertarget
What error appears if a reverse DNS lookup yields no PTR record?
a. Non-existent domain
b. Time-out
c. Unreachable host
d. REFUSED
Answer: a. Non-existent domainphoenixnap
In which aspect of cloud infrastructure management is reverse DNS critical?
a. Email delivery reliability
b. VM snapshots
c. Disk formatting
d. Licensing enforcement
Answer: a. Email delivery reliabilityfalconcloud
If a company’s IP block is 203.0.113.0/24, what reverse DNS zone is needed?
a. 113.0.203.in-addr.arpa
b. 0.113.203.in-addr.arpa
c. 203.113.0.in-addr.arpa
d. 0.0.0.0.in-addr.arpa
Answer: a. 113.0.203.in-addr.arparipe+1
What does “reverse mapping” mean in DNS?
a. Translating IP address to domain name
b. Converting MAC addresses to hostnames
c. Forwarding traffic to proxies
d. Encrypting DNS traffic
Answer: a. Translating IP address to domain namednschecker+1
Which record type must exist for every PTR record in DNS?
a. A record
b. AAAA record
c. MX record
d. TXT record
Answer: a. A recorddnschecker
Which DNS utility will display a PTR record when given an IP?
a. host
b. netstat
c. nbtstat
d. traceroute
Answer: a. hostphoenixnap
What is the role of reverse DNS in OSINT and penetration testing?
a. Discover additional hostnames for target mapping
b. Encrypt communication
c. Create VLAN tags
d. Block traffic
Answer: a. Discover additional hostnames for target mappinghackertarget
What info is stored in a reverse DNS PTR for IPv4 address 8.8.4.4?
a. Hostname dns.google
b. Zone file type
c. Email MX record
d. Block size
Answer: a. Hostname dns.googlednschecker
What reverse DNS format is used for IPv6 address 2001:db8::567:89ab?
a. b.a.9.8.7.6.5.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.2.ip6.arpa
b. 2.1.0.0.d.b.8.8.0.0.a.b.ip6.arpa
c. 2001.db8.567.89ab.ip6.arpa
d. 567.89ab.db8.2001.ip6.arpa
Answer: a. b.a.9.8.7.6.5.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.2.ip6.arparipe
What is the effect of incorrect PTR records for a mail server’s IP?
a. Emails are marked as spam or rejected
b. No impact
c. Emails reach only internal users
d. Users have delayed connections
Answer: a. Emails are marked as spam or rejectedmailmodo+1
For 1.2.168.192.in-addr.arpa, which IPv4 address does this refer to?
a. 192.168.2.1
b. 1.168.2.192
c. 168.192.1.2
d. 2.1.168.192
Answer: a. 192.168.2.1whatsmydns+2
Which DNS record provides the inverse function of an A record?
a. PTR record
b. CNAME record
c. AAAA record
d. NS record
Answer: a. PTR recordwhatsmydns+1
Reverse DNS lookups are essential for which network function?
a. Human-readable logging
b. Gzip compression
c. Port forwarding
d. DHCP negotiation
Answer: a. Human-readable logginggeeksforgeeks+1
Who must configure PTR records for reverse DNS to work?
a. Owner of the IP address block
b. Web host provider
c. Domain registrar
d. ISP network engineer
Answer: a. Owner of the IP address blockbigrock
What zone file entry would reverse map 5.2.0.192.in-addr.arpa to mail.example.com?
a. PTR mail.example.com
b. CNAME mail.example.com
c. MX mail.example.com
d. TXT mail.example.com
Answer: a. PTR mail.example.comripe
What utility on Linux can quickly perform reverse DNS lookups besides dig?
a. host
b. route
c. iptables
d. arp
Answer: a. hostphoenixnap
Why do spam filters check reverse DNS records?
a. To verify sender IP matches domain
b. To update recipient lists
c. To encrypt messages
d. To reroute messages
Answer: a. To verify sender IP matches domainmailmodo+1
What does a PTR record fail to provide if missing when an IP is queried?
a. The domain name for that IP
b. The MAC address
c. The server’s location
d. The port number
Answer: a. The domain name for that IPbigrock+1
Which online tool can show PTR records for a given IP?
a. DNSChecker
b. Nmap
c. Netcat
d. ipconfig
Answer: a. DNSCheckerdnschecker
What is one advantage of reverse DNS in server troubleshooting?
a. Enables tracking the origin of network issues using hostnames
b. Provides faster file transfers
c. Increases Wi-Fi speed
d. Prevents SYN floods
Answer: a. Enables tracking the origin of network issues using hostnamesgeeksforgeeks+1

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