2.5 Given a scenario, install & configure basic wired/wireless SOHO networks Flashcards
What is a protocol?
Rules for structured data communication among networked hosts
What are protocols often designed for?
Working together as a protocol suite
Most networks have converged on the use of the TCP/IP suite.
Why is the TCP/IP suite divided into layers?
To better understand the function of each protocol
In the TCP/IP, what does each lower protocol do?
Encapsulate data from higher-layer protocols
As data moves down the protocol stack, lower-layer protocols add their own headers before transmitting it
List the 4 layers of the TCP/IP suite
- Application
- Transport
- Internet
- Link (Network Interface)
Purpose of TCP/IP’s link layer?
Put frames onto the physical network
Which TCP/IP layer does not contain a TCP/IP protocol?
Link (Network interface) layer
What is used at the TCP/IP’s link layer?
LAN protocols & media
i.e. Ethernet or Wi-Fi
Where does communication on the TCP/IP’s link layer take place?
Only on a local network segment
Not between different networks
On an Ethernet or Wi-Fi segment, data at the link layer is packed into frames; node interfaces are identified by a MAC address
Purpose of TCP/IP’s Internet layer?
Address & routes packets across across a network of networks
(the Internet)
What is an “end system host”?
Device that can communicate on an IP network
i.e. PC, laptop, mobile device, server, etc.
What’s required to transmit IP packets over a physical/data link layer?
Like Ethernet or Wi-Fi
Mechanism to encapsulate IP packets within data link layer frames
What mechanism encapsulates IP packets within data link layer frames?
ARP
Meaning of ARP?
Address Resolution Protocol
What does ARP do?
Queries the MAC address associated with an IP address
2 types of delivery IP can provide?
Unreliable & connectionless delivery
A packet may be lost, delivered out of sequence, duplicated, or delayed
Purpose of TCP/IP’s Transport layer?
Manages multiple connections for application layer protocols
How is the TCP/IP’s Transport layer protocol implemented?
Via TCP or UDP protocol
What kind of packet delivery does TCP provide?
Connection-oriented packet delivery
TCP identifies & recovers lost or out-of-order packets, enhancing IP reliability. This is crucial for TCP/IP application protocols to prevent data errors.
What kind of packet delivery does UDP provide?
Connectionless packet delivery
UDP provides unreliable packet delivery
Which Transport layer protocol is faster?
UDP
Why is UDP faster than TCP?
Doesn’t send extra data for reliable connections
When is UDP used over TCP?
In time-sensitive applications where packet loss is tolerable
i.e. speech or video. Rather than causing the app to crash, they would just manifest as a glitch in video or a squeak in audio
What does the TCP/IP’s Application layer contain?
Protocols that perform a high-level function
Rather than simply addressing hosts & transporting data
What are Application protocols used for?
Managing network hosts & services
services like web & email
What does each application protocol use to connect clients to a server?
TCP or UDP ports
What are the 2 most important fields in an IP packet?
Source & destination IP address
2 versions of IP?
- IPv4
- IPv6
How long are IPv4 addresses?
32 bits
In its raw form, it appears as 11000000101010000000000000000001. These 32 bits can be divided into 4 groups of 8 bits, known as “octets”. The IP address is rearranged as 11000000 10101000 00000000 00000001, which is easier to read in dotted decimal notation (192.168.0.1).
What is the range of an IPv4 address?
0.0.0.0 to 255.255.255.255
However some addresses are not permitted or are reserved for special use
What 2 pieces of information do IPv4 addresses provide?
- Network ID
- Host ID
What does the Network ID in an IPv4 address identify?
The network to which a device belongs
The network ID is common to all hosts on the same IP network
What does the host ID in an IPv4 address identify?
A host within an IP network
What distinguishes the host & newtork ID of an IPv4 address?
Network prefix
What is a network prefix?
32-bit value with contiguous 1s identifing the network part of an IP address
i.e. a prefix with 24 bits means: 11111111 11111111 11111111 00000000. The prefix can be written in slash notation in the form /24
What is the dotted decimal expression of a network prefix called?
i.e. 255.255.255.0
Subnet mask
What does each binary 1 indicate in a subnet mask?
The corresponding bit in the IP address belongs to the Network ID
A subnet mask, like 255.255.255.0 (binary: 11111111.11111111.11111111.00000000), works with an IP address like 192.168.1.100 (binary: 11000000.10101000.00000001.01100100). Wherever the subnet mask has a 1, that part of the IP address is for the network, and where it has a 0, it’s for the host. So, in this case, the network ID is 192.168.1.0, and the host ID is 0.0.0.100.
What does this slash notation mean?
192.168.0.0/24
The first 24 bits represent the network ID
The network ID would be 192.168.0.
The last .0 is reserved as the network address, and .255 is often reserved as the broadcast address. So, for example, 192.168.0.1 to 192.168.0.254 would be assignable host addresses within the 192.168.0.0/24 network
What is slash notation often used for?
i.e. 192.168.0.0/24
To refer to network IDs
i.e. 192.168.0.0/24 refers to an IP network
What is a subnet mask often used for?
i.e. 255.255.255.0
Host configuration dialogs
i.e. 192.168.0.1/255.255.255.255 refers to a host address on that IP network
What happens when a host sends a packet via IPv4?
IPv4 compares source & destination IP address against the sending host’s subnet mask
What does IPv4 do if the masked portion of source & destination addresses don’t match?
Host assumes the packet must be routed to another IP network
What is the default gateway?
IP address of a router interface
Most hosts are configured with a default gateway parameter
What do hosts use default gateways for?
To forward packets to other networks
What is a requirement for a host to use a gateway address?
Both must be on the same IP network
What happens if hosts have a private IPv4 address?
Not allowed to route traffic over the public Internet
What is the use of private IPv4 addresses confined to?
Private LANs
3 private IPv4 address ranges?
- Class A
- Class B
- Class C
Class A private IPv4 address range?
10.0.0.0 to 10.255.255.255
Class B private IPv4 address range?
172.16.0.0 to 172.31.255.255
Class C private IPv4 address range?
192.168.0.0 to 192.168.255.255
What is the typical subnet mask for Class A private IPv4 addresses?
255.0.0.0
The network prefix for this is /8
What is the typical subnet mask for Class B private IPv4 addresses?
255.255.0.0
The network prefix for this is /16
What is the typical subnet mask for Class C private IPv4 addresses?
255.255.255.0
The network prefix for this is /24
2 ways hosts with private address can access the Internet?
- Via router with public addresses
- Via proxy server
Proxy server can fulfill requests for Internet resource on behalf of clients
How does a router convert between private & public IP addresses?
Using NAT
Meaning of NAT?
Network Address Translation
Minimum configuration a host needs to communicate on an IPv4 network?
IP address & subnet mask
This minimum setup isn’t very usable. More configurations are needed for a host to fully utilize a network or the Internet
What addresses cannot be assigned to a host in an IP network?
The first or last address
i.e. in the IP network 192.168.0.0/24, 192.168.0.0 is the first address & 192.168.0.255 is the last address
What is the first address in an IP network used for?
i.e. in the IP network 192.168.0.0/24, 192.168.0.0 is the first address
To identify the network itself
What is the last address in an IP network used for?
i.e. in the IP network 192.168.0.0/24, 192.168.0.255 is the last address
To broadcast to all hosts
What is the valid host address range in 192.168.0.0/24?
192.168.0.1 to 192.168.0.254
The first & last address arent included because theyre reserved for other uses
2 other parameters that make a host fully functional in an IPv4 network?
Besides an IP address & subnet mask
- Default gateway
- DNS server addresse(s)
What happens if a host is not configured with a default gateway?
Host can only communicate within the LAN
What is the primary DNS server address usually configured as?
The same as the gateway address
The router would be configured to forward DNS queries to a secure resolver. Often, 2 DNS server addresses are specified for redundancy
What does static IP addressing require?
Admin to enter config. info for each computer/host
Admin must keep track of which IP addresses have been allocated to avoid issuing duplicates
What happens if a host shifts to a new subnet with static addressing?
Admin must manually reconfigure it
Manually configuring IP addresses for every node in a large network is time-consuming and error-prone, risking communication disruptions
What are static IP addresses typically only assigned to?
Systems with a dedicated functionality
i.e. router interfaces or application server that need to use a fixed IP address
What is an alternative to static network configuration?
DHCP server
A host can receive its IP address, subnet mask, default gateway, & DNS server addresses
What occurs if a host can’t reach a DHCP server for network setup?
Uses an APIPA/link-local address
Meaning of APIPA?
Automatic Private IP Addressing
What is the range of an APIPA/link-local address?
169.254.0.1 to 169.254.255.254
What can a host with an APIPA/link-local address do?
Communicate with other hosts on the LAN using an APIPA/link-local address
What CAN’T a host do with an APIPA/link-local address?
Can’t reach other networks or communicate with DHCP hosts
Meaning hosts with a valid DHCP lease
Which vendor uses the term APIPA rather than “link-local”?
Microsoft
Other vendors & open-source products use the term “link local”
What may a host do if it can’t reach a DHCP server but doesn’t use APIPA/link-local addressing?
May leave the IP unconfigured or use the 0.0.0.0 IP address
it would use 0.0.0.0 to indicate that the IPv4 address of the interface is not known
What interfaces does a SOHO router have?
- Public digital modem interface
- Private Ethernet interface
The public digital modem is used to connect to the ISP. Ethernet is for LAN
What must both interfaces of a SOHO router be configured with?
Both interfaces = Public digital modem interface & private Ethernet interface
An IP address & subnet mask
Which SOHO router interface is used by hosts as the default gateway parameter?
LAN interface
This address is also used to access the router’s web management interface (i.e. https://192.168.0.1)
What is a router’s public interface IP address determined by?
ISP
It must be a valid public IP address. Internet service providers sometimes assign a static IP or offer it as an option for an additional fee. Otherwise, the public interface gets dynamically configured using the ISP’s DHCP server.
3 ways to tell if an IPv4 address is public?
- Not from a private range
- Doesn’t start with a 0
- Not a value of
224.x.y.zor above
Private range like 10.x.y.z, 172.16-32.x.y, or 192.168.0-255.x
The values 224.x.y.x & above is reserved for other types of addressing schemes
How to configure a SOHO router?
- Connect computer to router
- Load the device’s management URL on browser
Computer can be connected to router via RJ45 port or wireless network
The management URL could be an IP address or host/domain name (i.e. http://192.168.0.1 or http://www.routerlogin.com
What to do if you can’t connect to a router’s device management URL?
The management URL could be an IP address or host/domain name (i.e. http://192.168.0.1 or http://www.routerlogin.com
Verify if the computer’s IP address matches the router’s LAN IP range
How many bits are in a IPv6 address?
128
What can one hexadecimal digit express?
4-bit binary value
i.e. hex A = 1010
How is an IPv6 address constructed?
is divided into 8 double-byte values separated by colons
2001:0db8:0000:0000:0abc:0000:def0:1234
2 ways to shorten an IPv6 address?
- Ignore leading
0’s - Replace contiguous series of
0s with a double colon (::)
2001:0db8:0000:0000:0abc:0000:def0:1234 –> 2001:db8::abc:0:def0:1234
How is the network & host ID identified in an IPv6 address?
- First 64 bits = Network ID
- Last 64 bits = Host ID
i.e. in 2001:0db8:0000:0000:0abc:0000:def0:1234, the Network ID is 2001:0db8:0000:0000 & the Host ID is 0abc:0000:def0:1234
Why dont IPv6 address need a subnet mask?
The Network & host portions are a fixed size
What does prefix notation in IPv6 represent?
i.e. /32
The length of the routing prefix in bits
The length of the network prefix in IPv6 determines whether addresses belong to the same network. ISPs often assign /48 prefixes to customers for private networks, allowing up to 65,346 subnets to be configured.
2 types of IPv6 addresses IPv6 interfaces may be configured with?
- Global address
- Link-local address
IPv6 interfaces are more likely to be configured with multiple addresses
While it’s possible to configure IPv6 addresses statically, most hosts obtain a global & link-local address via local router
What are IPv6 global addresses used for?
Communicating over the Internet
This is the equivalent to IPv4 public addresses
What hex digit do IPv6 global addresses start with?
2 or 3
i.e. 2001:0db8:85a3:0000:0000:8a2e:0370:7334
What are IPv6 link-local addresses used for?
Communication between devices on the same LAN
What do IPv6 link-local addresses start with?
fe80::
What is SLAAC?
SLAAC = StateLess Address Auto Configuration
IPv6 method where devises self-assign addresses without a server
Central server like DHCP server
How do IPv6 hosts obtain a global & link-local address via router?
Through SLAAC
What network configuration do IPv6 hosts not need?
Default gateway
3 reasons IPv6 uses the Neighor Discovery (ND) protocol?
NDP is a protocol used in IPv6 to discover other devices on the same network, determine their link-layer addresses, find routers, and maintain reachability information about paths to active neighbors.
- To implement SLAAC
- Allow a host to discover a router
- Performs interface address query
“Performs interface address query” refers to a similar process to ARP in IPv4, where a device queries for the link-layer address (MAC address) associated with a specific IPv6 address on the LAN
What does a Dual Stack device refer to?
Device that can operate IPv4 & IPv6 simultaneously
A host first tries to establish an IPv6 connection and switches to IPv4 if the destination doesn’t support IPv6
What TCP/IP layer do WAN interfaces work at?
i.e. DSL & cable modems
Link (Network interface) layer
