Network Foundations
What is a set of rules established to exchange information?
A protocol.
How many layers are in the OSI model?
What layer of the OSI Model does a switch exist at?
How many bits are in a IPv4 address?
32 bits
What is the purpose of Internet Control Message Protocol (ICMP)?
ICMP is used to test and diagnose network problems.
What is a network?
A computer network is a telecommunications system that connects a collection of computers to allow communication and data exchange between systems, software applications and users.
What is the purpose of the network layer in the OSI model?
Network path determination
How is the source address table on a switch built?
From the source MAC address of an incoming Ethernet frame.
In IPv4, what is used along with the address to determine the network address?
The network mask
What is the purpose of traceroute?
Traceroute displays the route and delay from a source to a destination.
Consider the following network topology. Host A sends a message to Host B. What term best describes the message at the physical layer of the OSI model?
What is the process that occurs as a host is adding headers on a message?
Encapsulation!
What does a switch do when it receives a frame with a source address that is not already in a forwarding table?
The switch adds the address to the table for the port the frame came in through.
What is the default network mask for a Class B address?
255.255.0.0
What is the purpose of this ICMP message?
This is an ICMP echo request to test network connectivity.
How is the OSI Model different from the TCP/IP Model?
Many possibilities here:
- Layers
- OSI is conceptual whereas TCP/IP is Practice-Based
- The OSI Model was developed before the protocols, the TCP/IP Model was developed as a result of the protocols
Where does a switch forward a frame with an unknown unicast destination MAC?
The switch floods unknown unicast frames out all ports expect the incoming port.
How are IPv4 addresses different from MAC addresses?
Many ways:
Number of bits - MAC = 48 bits, IPv4 = 32 bits, IPv6 = 128 bits
Physical vs logical (MAC is physical - IP is logical)
Local vs remote
How does traceroute work? (What are the steps?)
2.) Packets repeatedly sent with the TTL value increasing
3.) Router sends an ICMP Time Exceeded message back to the source.
What does a host do after it receives an Ethernet frame, but before it processes the data?
1.) Checks to see if the destination MAC address is its own
2.) verifies that the frame meets the minimum size requirements
3.) checks the CRC
4.) checks that the frame does not exceed the maximum allowances.
Consider the following network topology. After Host A sends an echo request to Host B, what will the Source Address Table (SAT) on the switch look like?
Port | MAC
2 | A's MAC
What is the purpose of the network mask?
To identify the number of bits in the network address.
Command line vs graphical (nslookup = command line, whois = graphical)
NSlookup - query for the name and/or IP
Whois - querying registered users for Internet resources