Block 4 Networking Flashcards
Hub
Operates at the physical layer and does not separate collision domains
Repeater
Operates at the physical layer and boosts signals, twisted pair max length of 100m
Modem
Operates at the physical layer and converts from analog to digital
Media converter
Operates at the physical layer and allows connection between different media types
NIC
Network Interface Controller, allows physical and data link layer connections
Bridge
Operates in the data link layer, reduces amount of traffic on a LAN by dividing collision domains
Switch
Operates at the data link layer, each port is a collision domain
Wireless access point
Allows wireless access to wired network
Router
Operates at the network layer, connects two or more networks by forwarding packets between them, breaks up broadcast domains
How do routers select the best path for network packets
Using it’s routing table
Firewall
Operates between the network and transport layers, allows monitoring and control of network traffic
How do firewalls work?
They act on pre-determined rules to enable a barrier between trusted and untrusted connections and devices
What are the layers in the OSI model?
Physical, Data Link, Network, Transport, Session, Presentation, Application
What are the layers in the old TCP/IP Model?
Link, Internet, Transport, Application
What are the layers in the new TCP/IP model?
Physical, Data Link, Network, Transport, Application
What is the PDU of the application layer?
Data
What is the PDU of the transport layer?
Segment (TCP), Datagram (UDP)
What is the PDU of the network layer?
Packet or IP Datagram
What is the PDU of the data link layer?
Frame
What is the PDU of the physical layer?
Bit
What are some application layer protocols and services?
HTTP/S, POP3, SMTP, DNS, FTP, Telnet, SSH
What are some transport layer protocols and services?
TCP, UDP
What are some network layer protocols and services?
IP, ARP, ICMP, IPv4/Ipv6
What are some application/presentation/session layer devices?
Clients, servers, application layer security appliances
What devices operates between the transport and network layers?
Firewall
What are some network layer devices?
Router, multilayer switch
What are some data link layer devices?
Switch, bridge, wireless AP
What device operates between the data link and physical layer?
The NIC (Network Interface Controller)
What are some physical layer devices?
Hub, modem, repeater, cables, media converters
What are the different network topologies?
Bus, ring, star, mesh, hybrid
In a bus topology how many nodes will a failure affect?
All of them
Are rings unidirectional or bidirectional?
They can be both but if it’s unidirectional a secondary link is needed for redundancy
What two devices can be used to set up a star topology?
Switch and hub
If a star topology is set up using a switch it’s a logical what?
Star
If a star topology is set up using a hub it’s a logical what?
Bus
What are the advantages of a mesh topology?
Extremely reliable, provides redundancy and fault tolerance between devices
What are the disadvantages of a mesh topology?
High administrative overhead, full mesh requires exponentially more cabling
What are the advantages of a hybrid topology?
Flexible, reliable, increased fault tolerance, easy to expand, network faults can be easily diagnosed and corrected without affecting the rest of the network
What are the disadvantages of a hybrid topology?
Difficult to manage and expensive
Circuit-Switched Network
A sequence of links between two nodes is determined ahead of the actual communication, data is sent as a stream of bits
Packet Switched Network
Routers determine packet addressing, processes digital signals and routes information through multiple pathways
In which type of network does each data unit know the entire path address which is provided by the source?
Circuit switched
Resource reservation is a feature of what type of network?
Circuit switched
In which type of network does each data unit know only the final destination address and the path is determined by routers?
Packet switched
Virtual Circuit
The process of providing a connection oriented service between two hosts over a packet-switched network (TCP)
Supernetting
Routing protocols can summarize address of several networks into one
What are some advantages of supernetting?
Shrinks the routing table, improvers routing performance, quicker to send
Discontiguous Network
Two networks of the same classful networks are separated by a different network address
What is a limitation of older routing protocols?
The do not support discontiguous networks
What are the steps in Variable Length Subnet Masks (VLSM)?
- Order host requirements from largest to smallest
- Determine number of host bits needed
- Create smallest subnet needed for that host requirement
- Continue until all host requirements are met
What are some features of IPv4 that don’t exist in IPv6?
Subnet masks, network address, and broadcast address
What are the first 48 bits of an IPv6 address reserved for?
Networking/routing (usually from ISP)
What are bits 49-64 of an IPv6 address used for?
Subnets
What are the last 64 bits of an IPv6 address used for?
Hosts
In IPv6 once you determine the number of subnet bits you need what number do you add that to to get the mask?
48
Who developed the TCP/IP network model?
Defense Advanced Research Project Agency (DARPA)
Who developed the Open Systems Interconnect (OSI) model?
The International Organization for Standardization (ISO)
When was the TCP/IP model adopted?
The 1990s
Who developed the TCP/IP model?
It was a DoD led effort
What does TCP/IP use to define standardization protocols?
Request for Comments (RFC)
What is a Protocol Data Unit (PDU)?
Its a generic term for a unit of information being transmitted at a specific layer
What do application layer protocols do?
Provide services to the application software running on a computer, defines how programs interface with transport layer, functions include identifying communication partners, determining resource availability, and synchronizing communication
What is the DHCP protocol used for?
Assigning IP addresses
What ports does DHCP usually use?
UDP port 67 (client to server, broadcast)
UDP port 68 (server to client, unicast)
What will the server assign in DHCP?
IP address, lease, subnet mask, default gateway and possibly other options
DHCP uses what process?
Discover, Offer, Request, Acknowledge (DORA)
What is the Discover step in the DORA process?
Sent by the DHCP client to find a DHCP server (broadcast)
What is the Offer step in the DORA process?
Sent by the DHCP server to offer IP address and other parameters (unicast)
How do DHCP servers detect conflicts?
By using pings. They ping the address and if someone is using it the server receives a response
What is the Request step in the DORA process?
Reply from a client to the server accepting the offer. Contains server ID option so all DHCP servers know an offer was accepted (broadcast)
What is the Acknowledge step in the DORA process?
Sent by the DHCP server to acknowledge final phase and deliver DHCP lease information (unicast). Client will ARP new IP to verify it doesn’t overlap another
DNS
- TCP/UDP - port 53
- Hierarchical naming system
- Translates domain names into IP addresses
True/False DNS is a world wide service?
True
HTTP
- TCP 80 [8008, 8080]
- Protocol for the internet
- Request/response
- In between client and server may be several intermediaries
What does HTTP use for reliability?
TCP
How are servers identified in http?
URIs and URLs
HTTPS
- TCP 443
- URI/URL scheme used to indicate a secure HTTP connection
- Encrypts with digital certificate
- If NTP is not synchronized cert signing can fail
- Self signed certs provide confidentiality but don’t confirm identity
File Transfer Protocol (FTP)
- Default data TCP 20
- Control TCP 21
- Does not encrypt or protect data in transit
- Does not guarantee identity of sender or receiver
- Does provide authentication options
TFTP
- UDP port 69
- Very basic form of FTP
- Can only read and write files (or mail) from/to server
- No provisions for user authentication
- Typically used for storage and retrieval of Cisco IOS and Catalyst switch configuration files
TELNET
- Used for remote terminal connection
- TCP port 23
- Non secure