Section 1.6 Flashcards
How many dns root server clusters are there?
13
TLD
Top Level Domain
What are examples of some Top Level Domains?
.com
.net
.org
.gov
.edu
.(country)
FQDN
Fully Qualified Domain Name
What is a Fully Qualified Domain Name?
An FQDN has the subdomain/hostname, domain and top level domain.
What is the process of DNS resolution?
First, the computer checks its local cache. If not there, then the cache of the DNS resolver like the ISP or Google. If not there, then the TLD server.
What’s the difference between a non-authoritative answer vs an authoritative answer in a DNS lookup?
Non-authoritative is cached information, whereas authoritative is directly from the source.
What term determines how often the DNS cache is updated?
The Time To Live or TTL
In what increments of time is the domain TTL in?
number of seconds
Command for simple forward and reverse dns lookup
nslookup [domain/IP]
Command for detailed foward dns lookup
dig [domain]
Command for detailed reverse dns lookup
dig -x [IP]
NTP
Network Time Protocol
What keeps the time across a network synchronized?
an NTP server
What port does the NTP server listen on?
UDP 123
How is the level of accuracy rated on an NTP server?
by stratum layers. stratum 0, 1, or 2, where lower is more accurate
What are the DHCP steps?
- Discover from client to broadcast
- Offer from server to broadcast
- Request from client to broadcast
- Acknowledgement from server to broadcast
How is DHCP handled in large organizations?
Routers are configured with DHCP Relay or IP Helper, which forwards DHCP requests to the DHCP server
What are 5 components to a DHCP scope?
IP range (inclusion and exclusion)
Lease duration
Subnet mask
Default gateway
DNS server
How is an IP renewed by the client with a DHCP server?
At 50% of the lease time (T1), the client attempts to renew the IP with the original DHCP server
At 87.5% of the lease time (T2), if the lease hasn’t been renewed, the client tries to rebind with any available DHCP server
What’s the difference between a forward DNS lookup vs a reverse DNS lookup?
A forward lookup searches the domain name
A reverse lookup searches the IP address
What is the DNS hierarchy from top-down?
Root (.)
TLD (com/org)
SLD (wikipedia/google)
Subdomains (www/mail)
SLD
Second Level Domain
What is a DNS zone transfer and what’s their purpose?
They copy a DNS server to secondary servers to provide redundancy
What is an A record?
What does it map?
IPv4 Address record
Maps a domain name to an IPv4 address
What is a AAAA record?
What does it map?
IPv6 Address record
Maps a domain name to an IPv6 address
What is a CNAME record?
What does it map?
Canonical record
Maps domain name to aliases
What is an MX record?
What’s its purpose?
Mail Exchange record
Tells sender’s mail server where to deliver the message.
What is a TXT record?
What’s its purpose?
Text record
Stores text for verification and security
What is a PTR record?
What does it map?
Pointer record
Maps IP address to domain name
What is an NS record?
What does it map?
Name Server record
Maps domain to authoritative dns server
What is an SOA record?
What’s its purpose?
Start of Authority record
Contains the DNS zone details
What is an SRV record?
What’s its purpose?
Service record
Helps clients on network find another service
