1.8 - Network Services

Question 1

What are the DNS record types A and AAAA?

Answer 1

The records that hold the name-to-address mapping (conversion) for a given host. A = IPv4, AAAA = IPv6.

Question 2

What is a TXT record?

Answer 2

A Text record. Used to provide freely formatted text to network administrators regarding any network related issues or comments.

Question 3

What is SPF?

Answer 3

The Sender Provider Framework. A TXT file and part of the DNS zone file. Validates the e-mail servers allowed to send e-mail.

Question 4

What is DKIM?

Answer 4

DomainKeys Identified Mail. An encryption-based authentication method that validates the domain name of e-mails.

Question 5

What is SRV?

Answer 5

The service record. Contains hostname and port details for hosts providing specific services. Used for email, FTP, H.323, SIP, etc.

Question 6

What is MX?

Answer 6

Mail Exchanger record. Supports e-mail traffic by identifying e-mail servers.

Question 7

What is CNAME?

Answer 7

Canonical Name record. Contains the alias for a host’s CNAME. Allows a hostname alias like google to be identified by its canonical name www.google.com

Question 8

What is NS?

Answer 8

Name Server record. Specified the authoritative name server for a domain. Used by name servers to locate each other.

Question 9

What is PTR?

Answer 9

Pointer record. Consider it the opposite of the A record. Supports reverse look ups by providing the IP address-to-hostname in a reverse lookup zone file (reverse zone).

Question 10

Explain Internal DNS vs. External DNS

Answer 10

The external DNS is placed in the DMZ and will only provide access to public services like a web server or VPN. The internal DNS servers the domain and is inaccessible from the internet.

Question 11

Explain third-party/cloud hosted DNS

Answer 11

It can be more affordable to use cloud-based DNS as it is scalable, resilient, and secure. Administration is simplified. A large provider such as Google can reduce latency with its multiple geographical locations.

Question 12

Give me a rundown of DNS hierarchy

Answer 12

DNS root servers are shown as a dot at the top. Top level domains (TLDs), are things like .com, .org, .edu, .uk, etc. Second level domainds (SLDs) are things like microsoft, google, and wikipedia. Third level domainds are subdomains of SLDs. (Example: Play.google.com. Play = subdomain.)

Question 13

Explain MAC reservations

Answer 13

A MAC reservation can be created on your DHCP server to give a particular device the same IP address. Useful for printers, servers, etc.

Question 14

What is a DHCP pool?

Answer 14

AKA the DHCP scope. A predefined range of IP addresses.

Question 15

What are IP exclusions?

Answer 15

And IP exclusion removes the IP address from the DHCP server. This is useful when setting up static IPs.

Question 16

What are scope options?

Answer 16

Default gateway, primary or secondary DNS server, lease time are all scope options.

Question 17

What is TTL?

Answer 17

Time to Live. A value (usually 20 minutes) assigned to the DHCPOFFER after which the offer address is returned to the pool.

Question 18

What is DHCP relay/IP helper?

Answer 18

In a network with multiple LANs, DHCP relay can allow a single DHCP server to provide the necessary configurations. Useful with VLANs. The IP helper address provides support for rebroadcasting or forwarding of UDP packets across a router.

Question 19

What is IPAM?

Answer 19

IP address management. A software that can track, plan, and manage IP addressing on a network.