Network Configurations (2.1, 2.5 and 2.6) Flashcards
Where is the data limited to travelling in the link/network interface layer?
The local area network
What is the link/network interface layer responsible for?
Putting frames in the physical network’s transmission media
What is the internet layer used for?
Addressing packets and routing them across the network
What does the transport layer do?
Shows how to send the packets (using protocols e.g. TCP and UDP)
What does the application layer contain?
All the protocols that perform higher-level functions
Define multicast address
A logical identifier for a group of hosts in a computer network
What is a classful mask?
Default subnet mask for a given class of IP addresses
What does classless inter-domain routing (CIDR) allow?
Borrowing some of the host bits and reassigning them to the network portion
What is a public (routable) IP?
Can be accessed over the Internet and is assigned to the network by an ISP
Describe a private (non-routable) IP, including the numbers it could start with.
Can by used by anyone at any time but only within their own LAN. Ranges include those IPs that start with 10, 172 or 192
How can you route private IPs through a public IP?
By using network address translation (NAT).
What is a loopback address? Give the IP.
An address that creates a loopback to the host and is often used in troubleshooting and testing network protocols on a system. 127.0.0.1
When would automatic private IP addresses (APIPA) be used?
Give the IP range.
When a device does not have a static IP address or cannot reach a DHCP server.
169.254.0.0 to 169.254.255.255
What is the acronym for the process of obtaining an address from a DHCP server?
DORA: Discover, offer, request, acknowledge
How do you statically assign an IP address?
Manually type the IP address for the host, its subnet mask, default gateway and DNS server (impractical on large enterprise networks)
What does DNS do?
Converts the domain names used by a website to the IP address of its server (the internet version of a phonebook)
What does Windows Internet Name Service (WINS) do?
Identifies NetBIOS systems on a TCP/IP network and converts those names to IP addresses
What does Bootstrap Protocol (BOOTP) do?
Dynamically assigns IP addresses and allows a workstation to load a copy of a boot image to the network
What does DHCP do?
Give the IP range.
Assigns an IP based on an assignable scope of addresses and provides the ability to configure other options. Each IP is leased and returned to the pool when lease expires
192.168.1.100 to 192.168.1.200
What is the modern implementation of BOOTP?
DHCP
Name a positive and negative of APIPA.
- Allows for quick configuration of a LAN without the need for a DHCP server
- APIPA-assigned devices cannot communicate outside the LAN or with non-APIPA devices
What does ZeroConf do?
(Name three things.)
- Assigns IPv4 link-local addresses to a client
- Resolves computer names to IP addresses using mDNS
- Performs service discovery on a network (essentially the same features as APIPA)
What is ZeroConf called on Windows and Linux?
Windows: Link-local Multicast Name Resolution (LLMNR)
Linux: SystemD
What is scope (in context of DHCP)?
The list of valid IP addresses available for assignment or lease to a client computer or endpoint device on a given subnet. There are 254.
What does DHCP do?
Provides an IP address to every machine on the network and eliminates configuration errors
What is DHCP reservation?
Excluding some IP addresses from being handed to devices unless they meet a certain condition
How does DNS help network clients find a website?
By using human-readable hostnames instead of numeric IP addresses
Define a fully-qualified domain name (FQDN).
A domain name under a top-level provider
What does the Uniform Resource Locator (URL) contain?
The FQDN with the method of accessing information
What can CNAME records be used for?
To point to another domain or subdomain (not to an IP address)
What DNS record has the function of linking a hostname to an IPv6 address?
AAAA
Define Sender Policy Framework (SPF).
A DNS record that identifies the host authorised to send mail for the domain
What does DKIM do?
Provides the cryptographic authentication mechanism for mail using a public key published as a DNS record
What is DMARC?
A framework that is used for proper application of SPF and DKIM, utilising a policy that is published as a DNS record
What is a nameserver?
A type of DNS server that stores all the DNS records for a given domain
What does internal DNS do?
Allows cloud instances on the same network to access each other using internal DNS names
What is external DNS?
Records created around the domain names from a central authority and used on the public Internet
What is the function of Time to Live (TTL)?
It tells the DNS resolver how long to cache a query before requesting a new one
What does the DNS cache do?
Makes a local copy of every DNS entry it resolves
How does a recursive lookup work?
A DNS server communicates with several other DNS servers to hunt down the IP address and return to the client
How does an iterative lookup work?
Each DNS server responds directly to the client with an address for another DNS server that may have the correct IP address
What is VLAN trunking?
Where multiple VLANS are transmitted over the same physical cable
Name two benefits of a VLAN.
- Allows different logical networks to share the same physical hardware
(switch ports can be in different VLANs) - Provides added security and efficiency
Name two 4-byte identifiers.
- Tag Protocol Identifier (TPI)
- Tag Control Identifier (TCI)
What is the name given to the untagged VLAN?
The native VLAN
What does a VPN do?
Name the two different types.
Extends a private network across a public network and enables sending and receiving data across shared or public networks.
Site to site or Client to site
How does a full tunnel VPN work?
Routes and encrypts all network requests through the VPN connection back to the headquarters
What does a split tunnel VPN do?
Routes and encrypts only the traffic bound for the headquarters over the VPN and sends the rest of the traffic to the regular Internet
Why would you use a clientless VPN?
When you want a secure remote-access VPN tunnel using a web browser, without using a software or hardware client
What does secure socket layer (SSL) do?
Provides cryptography and reliability using the upper layers of the OSI model (5, 6 and 7)
What does transport layer security (TLS) do?
Provides secure web browsing over HTTPS
How many addresses are there in each of IPv4 and IPv6?
IPv4: 4.2 billion (2^32)
IPv6: 340 undecillion (2^128)
List five concepts from the experimental protocol IPv5 that have been incorporated into IPv6.
- Larger address space
- No broadcasts
- No fragmentation
- Can coexist with IPv4
- Simplified header
When would you need a dual stack?
When you need to run both IPv4 and v6 protocols on the same network devices
How can you get an existing IPv4 router to carry IPv6 traffic?
By creating a tunnel
Which IP version uses hexadecimal digits and allows the use of shorthand notation?
IPv6
Which IP version includes the TTL, payload and header checksum in its header?
IPv4
What is a unicast address used for?
To identify a single interface
Describe globally-routed unicast address.
Similar to IPv4’s unicast class A, B and C addresses; begins with 2000-3999
Describe link-local/local use unicast address
Used like a private IP in IPv4 that can only be used on the LAN and begins with FE80
What does stateless address autoconfiguration (SLAAC) do?
Eliminates the need to obtain addresses or other configuration information from a central server
What is a multicast address used for, and what does it begin with?
Used to identify a set of interfaces; begins with FF
What is the purpose of an anycast address?
To identify a set of interfaces so that a packet can be sent to any member of a set
What does an Extended Unique Identifier (EUI) do?
Allows a host to assign itself a unique 64-bit IPv6 interface identifier called EUI-64
What does the DHCPv6 protocol do?
Allows DHCP to automatically assign addresses from a DHCPv6 server
Define a port.
A logical communication endpoint that exists on a compouter or server
Define an inbound port.
A logical communication opening on a server that is listening for a connection from a client
Define an outbound port.
A logical communication opening created on a client in order to call out to a server that is listening for a connection
What number can ports have?
Any number between 0 and 65535
What are well-known ports?
Ports 0 to 1023; they are assigned by the Internet Assigned Numbers Authority (IANA)
Which ports are considered registered and usually assigned to proprietary protocols?
1024 to 49151
Which port numbers would you be able to use without them being registered with IANA? What are these ports called?
49152 to 65535
Dynamic/private ports
What protocol uses ports 20 and 21, and what does it do?
FTP; provides insecure file transfers
What port does SSH use and what does it do?
Port 22; provides secure remote control of another machine using a text-based environment
What port does SFTP use and what does it do?
Port 22; provides secure file transfers
Give the protocol and port from this description:
“Provides insecure remote control of another machine using a text-based environment.”
Telnet, port 23
Give the protocol and port from this description:
“Converts domain names to IP addresses and IP addresses to domain names.”
DNS, port 53
What port does SMTP use?
Port 25
What ports does DHCP use?
Port 67 and 68
Which port does HTTP use for insecure web browsing?
Port 80
Which port does Post Office Protocol Version Three (POP3) use, and for what?
Port 110; used for receiving incoming emails
Give the port/s and use for the NetBIOS
Ports 137 and 139; used for file or printer sharing in a Windows network
What protocol improves upon POP3 and what port does it use?
Internet Mail Application Protocol (IMAP); port 143
Name the protocol that uses these ports (and what it is used for): Ports 161 and 162
Simple Network Management Protocol (SNMP); it is used to collect data about network devices and monitor their status
Name the protocol that uses this port and what it is used for: Port 389
LDAP; used to provide directory services to the network
Which port does HTTPS use?
Port 443
What security measures does HTTPS use?
Secure Socket Layer and Transport Layer Security
What port does Server Message Block use and what is it used for?
Port 445; used for Windows file and printer sharing services
Give the protocol and the port from the below description:
“Provides graphical remote control of another client or server.”
Remote Desktop Protocol (RDP); port 3389
Is TCP or UDP more reliable, and why?
TCP is more reliable because it requires a three-way handshake before transmitting any data
Which protocols are TCP (connection-oriented)?
- SSH
- HTTP
- HTTPS
Which protocols are UDP (connectionless)?
- Audio
- Video streaming
- DHCP
- TFTP
Which protocol, TCP or UDP, enables segment retransmission and flow control (windowing)?
TCP
Port 69 supports what protocol?
Trivial File Transfer Protocol (TFTP), a connectionless protocol that uses UDP as its transport.
