CompTIA Network+ Exam Prep

120 flashcards by MentisLibrary

The Network+ objectives as study items: port numbers, cabling and media, IPv4 and IPv6 addressing, routing and switching, wireless, network services, security controls, operations and the seven-step troubleshooting method.

What are the five Network+ domains?
Networking concepts, network implementation, network operations, network security and network troubleshooting.
Name the OSI layers in order from 1 to 7
Physical, Data Link, Network, Transport, Session, Presentation, Application.
Which OSI layer does a switch work at, and a router?
A switch forwards frames by MAC address at layer 2. A router forwards packets by IP address at layer 3. A multilayer switch does both in hardware.
TCP versus UDP
TCP is connection-oriented with sequence numbers, acknowledgments, flow control and retransmission, and a 20-byte minimum header. UDP is connectionless with an 8-byte header and no delivery guarantee.
The TCP three-way handshake
SYN from the client, SYN-ACK from the server, ACK from the client. Sequence numbers are synchronized and the connection is established.
IP protocol numbers worth recognizing
1 is ICMP, 6 is TCP, 17 is UDP, 47 is GRE, 50 is ESP and 51 is AH.
Three-tier campus design versus spine and leaf
The three-tier design is core, distribution and access, built for traffic heading in and out. Spine and leaf connects every leaf switch to every spine switch, giving equal-cost paths and predictable latency between servers.
Software-defined networking planes
The data plane forwards traffic, the control plane decides where traffic should go, and the management plane configures and monitors. SDN moves the control plane into a central controller.
What is a VLAN and what does 802.1Q add?
A VLAN is a logical layer 2 segment that separates broadcast domains on shared hardware. 802.1Q inserts a 4-byte tag holding the VLAN ID into the Ethernet frame so a single trunk carries many VLANs.
Full duplex, half duplex and the mismatch symptom
Full duplex transmits and receives at the same time. Half duplex does one at a time and uses CSMA/CD to handle collisions. A duplex mismatch leaves the link up but produces late collisions and FCS errors.
MTU and what happens when a packet exceeds it
The maximum transmission unit is the largest payload a frame will carry, 1500 bytes by default on Ethernet. Oversized packets are fragmented, or dropped if the do-not-fragment bit is set.
Twisted pair category speeds and distances
Cat 5e carries 1 Gb/s to 100 m. Cat 6 carries 10 Gb/s to 55 m and 1 Gb/s to 100 m. Cat 6a carries 10 Gb/s over the full 100 m. Cat 8 carries 25 or 40 Gb/s but only to about 30 m.
Maximum copper Ethernet channel length
100 meters, made up of 90 meters of permanent horizontal cable plus about 10 meters of patch cords at each end.
Fiber connector types you must recognize
LC and SC are the common connectors, LC being the smaller of the two. ST is the older bayonet twist-lock. MTRJ is a small duplex connector, and MPO carries 12 or 24 fibers in one ferrule for 40 and 100 Gb/s links.
Transceiver form factors and their speeds
SFP up to 1 Gb/s, SFP+ 10 Gb/s, SFP28 25 Gb/s, QSFP+ 40 Gb/s and QSFP28 100 Gb/s.
How do you read an Ethernet standard name like 10GBASE-LR?
The number is the speed in Mb/s or Gb/s, BASE means baseband signaling, and the suffix names the medium. LR is long-reach single-mode fiber, SR is short-reach multimode and T is twisted pair.
Coaxial cable types and impedance
RG-6 carries cable television and cable internet with an F-connector; RG-59 is the older, thinner cable used for short video runs. Both are 75 ohm.
What is attenuation and how do you fix it?
Signal strength lost over distance. Shorten the run, move to a higher grade cable or fiber, or put a switch or repeater in the middle.
Crosstalk, NEXT and FEXT
Signal from one pair bleeding into another. Near-end crosstalk is measured at the transmitting end and far-end crosstalk at the opposite end.
T568A and T568B wiring
Two pin-out standards for terminating twisted pair. Either works as long as both ends match. A cable wired T568A on one end and T568B on the other is a crossover.
Power over Ethernet standards and power budgets
802.3af (PoE) supplies 15.4 W at the source and about 12.95 W at the device. 802.3at (PoE+) supplies 30 W. 802.3bt Type 3 supplies 60 W and Type 4 up to 100 W.
When is plenum-rated cable required?
In any air-handling space, because a plenum jacket gives off far less toxic smoke when it burns. Riser cable runs vertically between floors but not in return-air spaces.
Cable tester versus TDR versus OTDR
A cable tester proves continuity and pin mapping. A time domain reflectometer reports the distance to a fault on copper. An optical time domain reflectometer does the same on fiber and also measures splice and connector loss.
RFC 1918 private address ranges
10.0.0.0/8, 172.16.0.0/12 which ends at 172.31.255.255, and 192.168.0.0/16. They are not routed on the internet and need NAT to reach it.
How many usable hosts does a /26 provide?
62. Six host bits give 64 addresses, minus the network and broadcast addresses.
Find the network and broadcast address for 172.16.40.100/22
Network 172.16.40.0 and broadcast 172.16.43.255, with usable addresses from 172.16.40.1 to 172.16.43.254.
CIDR and VLSM
Classless inter-domain routing drops the old address classes and lets any prefix length be used. Variable length subnet masking applies different prefix lengths inside one network so each subnet is sized to its host count.
When would you use a /31?
On a point-to-point link. RFC 3021 allows both addresses in a /31 to be assigned, so a router-to-router link uses two addresses instead of the four a /30 consumes.
What does an APIPA address indicate?
The host failed to reach a DHCP server and self-assigned an address from 169.254.0.0/16. It can only communicate on the local link.
NAT versus PAT
NAT maps one inside address to one outside address. PAT, also called NAT overload, maps many inside addresses to one outside address by tracking unique source port numbers.