SysAdmin

Question 1

Microsoft IIS, Apache, nginx

Answer 1

A few of the most popular web servers

Question 2

DNS

Domain name system

Answer 2

Network service that converts a webpage’s domain name into its IP address

Allows a company to host multiple servers around the world with the same domain name, or to change IP addresses without affecting customers

Question 3

4 things you need to connect a network to the internet

Answer 3

IP address, subnet mask, gateway router, and DNS

not totally sure about this one!

Question 4

5 types of DNS servers

Answer 4

Caching, recursive, root, TLD (top level domain), authoritative

(good diagram of how they work together in Course 2 notes p 15)

Question 5

Caching name server

Answer 5

DNS server that simply stores known domain names for a certain amount of time

Usually provided by your ISP; most are also recursive servers

Question 6

Recursive name server

Answer 6

DNS server that performs full DNS resolution requests

Usually provided by your ISP

Question 7

Root name server

Answer 7

DNS server that is the first stop when your caching/recursive name server needs to find an IP address

Includes 13 authorities, and your request can go to any of them

Question 8

TLD (top-level domain) name server

Answer 8

Top-level domain is the .com or .edu (for example) part of a domain name

Each TLD has a server, which is really a series of Anycast servers

Question 9

Authoritative name server

Answer 9

DNS server that provides the IP address requested

This is usually a server controlled by the organization that runs the website in question

Question 10

Anycast

Answer 10

Technique that routes traffic to different internet destinations based on location, traffic, and other factors

Allows for multiple servers, frequently spread across the globe, to function as one server

Question 11

DNS time to live (TTL)

Answer 11

How long (in seconds) a DNS server can cache an entry; set by the owner of the domain name

Usually a few minutes to a few hours

Question 12

A record

Answer 12

Connects a certain domain name to a certain IPv4 address

A busy domain name (ex: google.com or facebook.com) will have multiple IP addresses and an A record for each

Question 13

Quad A (AAAA) record

Answer 13

Connects a certain domain name to a certain IPv6 address

Question 14

CNAME record

canonical name record

Answer 14

Directs traffic from one domain name to another

ex: weather.com to www.weather.com

Question 15

Fully qualified domain name (FQDN)

Answer 15

Includes subdomain (www), domain (palmbeachzoo), and top-level domain (.org)

Question 16

DNS zones

Answer 16

Part of a large company served by a particular authoritative name server

Ex: a company with business centers in LA, Shanghai and Paris might have 4 authoritative servers, one for company.com, and one for each subdomain (la.company.com, etc.)

Question 17

DNS zone files

Answer 17

Simple configuration files that list all resource records (ex: A and Quad A records) for a particular zone

Question 18

DHCP

Dynamic Host Configuration Protocol

Answer 18

Application layer protocol that assigns IP addresses to devices in a network

Good for clients, but servers should have a fixed IP address

Question 19

DHCP allocation options (dynamic, automatic, fixed)

Answer 19

Dynamic allocation - DNS server issues a random IP address from its range each time a device connects; most common

Auto allocation - DNS server keeps track of devices’ last IP address, and gives the same one back if possible

Fixed allocation - can be a security feature to disable dynamic/auto allocation (a device that hasn’t been assigned a fixed IP address won’t be able to connect)

Question 20

NTP

Network time protocol

Answer 20

NTP server keeps all computers on your network synchronized

DHCP usually handles this

Question 21

DHCP discovery

Answer 21

Process a client devices uses to “ask for” an IP address and the other info (such as gateway IP and subnet mask) it needs to connect to the network

Question 22

DHCP lease

Answer 22

Temporary IP address assigned to a client by a DNS server

Can be good for a few days or just a short time

Question 23

NAT

Network Address Translation

Answer 23

Technology that allows a gateway (usually a router or firewall) to rewrite the source IP of an outgoing IP datagram, and send the response back to the correct device

Allows most of a network’s computers to use non-routable IP addresses

Question 24

IP masquerading

Answer 24

Hiding a computer’s IP address (usually through Network Address Translation)

Prevents unauthorized devices from connecting to the computer

Question 25

Port forwarding

Answer 25

An option in NAT (network address translation) where messages to a certain port are always delivered to a particular host

Ex: a gateway router is set to always send traffic with destination port 80 to the company’s web server