CISSE Intermediate Level
Networking and Data Communication flashcards
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Name the seven OSI layers from top (7) to bottom (1).
7 Application, 6 Presentation, 5 Session, 4 Transport, 3 Network, 2 Data Link, 1 Physical. Mnemonic, top to bottom: All People Seem To Need Data Processing.
192.168.10.0/24 is split into 8 equal subnets. What is the new prefix, the block size and the number of usable hosts per subnet?
8 subnets needs 3 borrowed bits, since 2^3 = 8, so the prefix becomes /24 + 3 = /27. Block size: 256 / 8 = 32 addresses. Usable hosts: 32 - 2 = 30 (the network and broadcast addresses are not usable). First subnet: 192.168.10.0/27, hosts .1-.30, broadcast .31.
What is the difference between a hub and a switch?
A hub repeats incoming data to every connected port, and is largely obsolete. A switch learns MAC addresses and forwards data only to the port it is addressed to, so it is both faster and more secure. It is the standard LAN connectivity device today.
How do TCP and UDP differ, and what does each suit?
TCP: connection-oriented (a handshake first) and reliable, guaranteeing delivery and correct order by retransmitting lost data. Suits web browsing, file transfer and email. UDP: connectionless and unreliable, with no delivery guarantee or retransmission. Suits video and voice streaming and DNS queries, where speed matters more.
When is fibre-optic cable chosen over twisted pair?
Twisted pair (UTP/STP) is the standard, inexpensive Ethernet LAN cabling, limited to about 100 metres. Fibre carries light rather than an electrical signal, giving far higher bandwidth and distance and immunity to electromagnetic interference, so it is used for backbone and long-distance links.
What is the difference between static and dynamic routing?
Static routing: routes configured by hand by an administrator. Predictable, but does not adapt automatically to a topology change. Dynamic routing: routers exchange information and adapt routes as the network changes, e.g. RIP, OSPF, EIGRP. Needed as a network grows beyond what static routing can manage by hand.
Rank WEP, WPA, WPA2 and WPA3, and say why WEP should not be used.
WEP: an early standard, broken; its encryption can be cracked quickly with widely available tools. WPA: improved on WEP, later superseded. WPA2: the long-standing standard using AES encryption, still widely deployed. WPA3: the current standard, with stronger protection against offline password-guessing attacks.
Why is SSH preferred to Telnet for remote access to a router?
Both give remote command-line access. SSH encrypts the whole session, credentials included. Telnet sends everything, login credentials included, in unencrypted plain text, so it is insecure on any network an untrusted party can reach.
List the six steps of the structured troubleshooting process, in order.
1. Identify the problem: gather symptoms and information from the user. 2. Establish a theory of probable cause. 3. Test the theory to determine the actual cause. 4. Establish a plan of action and implement the fix. 5. Verify full system functionality. 6. Document findings and the resolution.
What are the three transmission modes, with an example of each?
Simplex: one direction only, e.g. a broadcast radio signal. Half-duplex: both directions, but only one at a time, e.g. a walkie-talkie. Full-duplex: both directions simultaneously, e.g. a telephone call.
What scope does each network type cover: PAN, LAN, MAN, WAN?
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What is the difference between a workgroup and a domain?
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What does a network adapter (NIC) do, and what address does it carry?
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What does a router do, and what does an access point do?
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What is the difference between an end device and an intermediary device?
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What is a peer-to-peer network, and what is its trade-off?
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Name the three wireless media and what each is used for.
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What is cable termination, and why does it matter?
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What are the four TCP/IP layers, and which OSI layers does each roughly cover?
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State four benefits of a layered networking model.
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What are encapsulation and de-encapsulation?
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What does each body do: IEEE, IETF, ISO, ITU?
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Give the trade-off of each physical topology: bus, star, ring, mesh.
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Why can a star-cabled Ethernet network be described as a logical bus?
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What is a Passive Optical Network (PON)?
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Give the first-octet range and default use of IPv4 classes A to D.
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What does CIDR notation such as 192.168.1.0/24 express, and why did it replace classes?
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List the four subnets of 192.168.1.0/24 subnetted to /26.
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172.16.0.0/16 is subnetted to /18. How many subnets, and how many usable hosts in each?
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Define the IPv6 address types: unicast, multicast, anycast, global unicast, link-local.
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Why was IPv6 developed, and how is an IPv6 network typically subnetted?
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When is an address configured statically, and when dynamically?
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What are the three port number groups, with the well-known ports for HTTP, HTTPS, SSH and DNS?
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What does the netstat utility display, and what is it used for?
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What three things are given when configuring a static route on a router?
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What does DHCP assign to a device joining the network?
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What does DNS do?
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What is the weakness of traditional FTP, and what addresses it?
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What is the difference between a collision domain and a broadcast domain?
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What is a VLAN, and what are its two benefits?
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At which OSI layers do a router and a multilayer switch operate?
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Why is inter-VLAN routing needed, and what are the two ways to do it?
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Name five threats to a wireless LAN.
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How is a wireless router usually configured, and what is set there?
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What is the trade-off between a public and a private WAN?
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Describe four WAN technologies: leased line, MPLS, VPN over the internet, satellite.
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What do syslog and NTP do, and why does syslog depend on NTP?
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What does each tool do: ping, traceroute/tracert, ipconfig/ifconfig, cable tester, protocol analyser?
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Give the typical sequence for troubleshooting IP connectivity.
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In what order is a LAN built and configured in the hands-on design exercise?
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Why do networks exist, and what five services does a network provide?
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How does digital transmission differ from analog, and what makes digital the basis of modern data networks?
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Where does coaxial cable stand among the guided media today?
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Fibre beats twisted pair on bandwidth, distance and interference immunity. What does copper offer in return, and what should a scenario answer be anchored to?
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What does a network's topology describe, and in which two senses?
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One cable breaks. What is the effect in a bus network, and in a star network?
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Telnet is largely superseded by SSH. Where might it still be found, and why is that a problem?
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A 24-port switch with no VLANs has a computer on every port. How many collision domains and broadcast domains are there?
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Name the four WLAN components and the role of each.
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An employee plugs a personal wireless access point into the office network without IT's knowledge. What threat is this, and why does it matter?
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Why do WAN links follow standards set by bodies such as the ITU and industry telecom consortiums?
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What is Carrier Ethernet, and what is its advantage for linking sites?
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A firm on a limited budget must link two branches and carry sensitive data securely over shared infrastructure. Which WAN technology fits, and why not a leased line?
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Why do devices send syslog messages to a central server, and what are a message's facility and severity?
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In what three roles can a device operate in NTP?
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What does configuring NTP on a router or Layer-3 switch involve, and what must be checked before trusting its logs?
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How does a protocol analyser such as Wireshark differ from netstat?
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What network documentation underpins troubleshooting, and what happens without it?
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How do bottom-up and top-down troubleshooting differ, and what does the OSI model add?
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When building a LAN, what decides the cable and connector chosen for each link?
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How does building an internetwork in simulation software differ from building it physically, and what is the advantage?
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In a lab, computers on two subnets each reach their own default gateway but not each other. What is missing, and why?
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Why configure the router as a DHCP server in a LAN build, and what is checked afterwards?
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