Comnet 2 Quiz Flashcards
is a contention-based media access method that allows all hosts on a
network to share the same link’s bandwidth
Ethernet
uses both Data Link and Physical layer specifications, presented with
information relative to both layers, and need to effectively implement,
troubleshoot, and maintain an Ethernet network.
Ethernet
refers to a network scenario wherein one device sends a frame
out on a physical network segment forcing every other device on the same
segment to pay attention to it
Collision Domain
refers to a group of devices on a specific
network segment that hear all the broadcasts sent out on that
specific network segment.
Broadcast Domain
is usually a boundary delimited by physical
media like switches and routers, the term can also refer to a logical
division of a network segment, where all hosts can communicate via a
Data Link layer, hardware address broadcast.
Broadcast Domain
helps
devices share the bandwidth evenly while preventing two devices from
transmitting simultaneously on the same network medium.
Carrier Sense Multiple access with collision detection (CSMA/CD)
created to overcome the problem of the collisions that
occur when packets are transmitted from different nodes at the same time.
CSMA/CD
When a collision occurs on an Ethernet LAN, the following happens:
- A jam signal informs all devices that a collision occurred.
- The collision invokes a random backoff algorithm.
- Each device on the Ethernet segment stops transmitting for a short time until
its backoff timer expires. - All hosts have equal priority to transmit after the timers have expired.
defined in the original IEEE 802.3 Ethernet
specification, Cisco says Ethernet uses only one wire pair with a digital signal
running in both directions on the wire.
Half-Duplex Ethernet
uses the CSMA/CD protocol I just discussed to help prevent
collisions and to permit retransmitting if one occurs.
Half Duplex
The Six situations that you can full-duplex ethernet:
- With a connection from a switch to a host
- With a connection from a switch to a switch
- With a connection from a host to a host
- With a connection from a switch to a router
- With a connection from a router to a router
- With a connection from a router to a hos
decides on the exchange capability, which
means it checks to see if it can run at 10, 100, or even 1000 Mbps. It
then checks to see if it can run full-duplex, and if it can’t, it will run half-
duplex.
Auto-detect mechanism
Important points in Full-Duplex:
- There are no collisions in full-duplex mode.
- A dedicated switch port is required for each full-duplex node.
- The host network card and the switch port must be capable of
operating in full-duplex mode. - The default behavior of 10Base-T and 100Base-T hosts is 10 Mbps
half-duplex if the autodetect mechanism fails, so it is always good
practice to set the speed and duplex of each port on a switch if you
can.
responsible for Ethernet addressing,
commonly referred to as MAC or hardware addressing.
Ethernet at the Data Link layer
responsible for framing packets received from the
Network layer and preparing them for transmission on the local
network through the Ethernet contention-based media access
method.
Ethernet
• It uses the Media Access Control (MAC) address burned into each and
every Ethernet network interface card (NIC).
Ethernet Addressing
is assigned by the IEEE to an
organization. It’s composed of 24 bits, or 3 bytes, and it in turn assigns
a globally administered address also made up of 24 bits, or 3 bytes,
that’s supposedly unique to each and every adapter an organization
manufactures.
Organizationally Unique Identifier(OUI)
When it has a
value of _, we can assume that the address is the MAC address of a
device and that it may well appear in the source portion of the MAC
header.
0
When it’s a _, we can assume that the address represents either a
broadcast or multicast address in Ethernet.
1
sometimes called the G/L bit or
U/L bit, where U means universal.
Global/Local Bit
The use to limit order 1 and 0
Binary
group either 4 or 8 buts togethe
Nible and byte
are placed in a value spot, starting at the right
and moving left, with each spot having double the value of the
previous spot.
Binary Numbers
Which is a numbering system that uses the
first six letters of the alpha
Hex is short for Hexadecimal
responsible for combining bits into bytes and
bytes into frames.
• MAC frame format it provides error detection from a cyclic
redundancy check (CRC)
Data Link Layer
Encapsulating a frame within a different type of frame is called
Tunneling
An alternating 1,0 pattern provides a 5 MHz clock at the start of each
packet,
which allows the receiving devices to lock the incoming bit stream.
Preamble
h The preamble is seven octets and the SFD is one
octet (synch). The SFD is 10101011, where the last pair of 1s allows the receiver to
come into the alternating 1,0 pattern somewhere in the middle and still sync up to
detect the beginning of the data
Start Frame Delimiter (SFD)SYNCH
This transmits a 48-bit value using the least significant bit
(LSB) first. The DA is used by receiving stations to determine whether an incoming
packet is addressed to a particular node. The destination address can be an individual
address or a broadcast or multicast MAC address. Remember that a broadcast is all
1s—all Fs in hex— and is sent to all devices. A multicast is sent only to a similar subset
of nodes on a network
Destination Address
a 48-bit MAC address used to identify the
transmitting device, and it uses the least significant bit first. Broadcast and
multicast address formats are illegal within the SA field
Source Address
uses a Length field, but the Ethernet_II frame uses a
Type field to identify the Network layer protocol. The old, original 802.3
cannot identify the upper-layer protocol and must be used with a
proprietary LAN—IPX, for example
Length or type 802.3
is a field at the end of the frame that’s
used to store the cyclic redundancy check (CRC) answer
Frame Check Sequence (FCS)
is a
mathematical algorithm that’s run when each frame is built based on the
data in the frame. When a receiving host receives the frame and runs the
CRC, the answer should be the same. If not, the frame is discarded,
assuming errors have occurred
Cyclic Redundancy check
they created and implemented the first
Ethernet LAN specification, which the IEEE used to create the IEEE 802.3
committee.
• This was a 10 Mbps network that ran on coax and then eventually twisted-
pair and fiber physical media.
Digital, Intel, and Xerox
is the standards body that creates
the Physical layer specifications for Ethernet.
EIA/TIA (Electronic Industries Alliance and the newer
Telecommunications Industry Association)
10 Mbps using category 3 unshielded twisted pair (UTP)
wiring for runs up to 100 meter
10Base-T (IEEE 802.3)
most commonly known as Fast
Ethernet, uses EIA/TIA category 5, 5E, or 6 UTP two-pair wiring. One user per
segment; up to 100 meters long. It uses an RJ45 connector with a physical star
topology and a logical bus.
100Base-TX (IEEE802.3u)
Uses fiber cabling 62.5/125-micron multimode fiber.
Point- to- point topology; up to 412 meters long. It uses ST and SC connectors,
which are media interface connectors.
100Base-FX (IEEE 802.3u)
Copper twisted-pair, called twinax, is a balanced
coaxial pair that can run only up to 25 meters and uses a special 9-pin
connector known as the High Speed Serial Data Connector (HSSDC). This is
used in Cisco’s new Data Center technologies.
1000Base-CX (IEEE 802.3z)
Category 5, four-pair UTP wiring up to 100 meters
long and up to 1 Gbps
1000Base-T (IEEE 802.3ab)
The implementation of 1 Gigabit Ethernet running
over multimode fiber-optic cable instead of copper twisted-pair cable, using
short wavelength laser. Multimode fiber (MMF) using 62.5- and 50-micron
core; uses an 850 nanometer (nm) laser and can go up to 220 meters with
62.5-micron, 550 meters with 50-micron.
1000Base-SX (IEEE 802.3z)
Single-mode fiber that uses a 9-micron core and
1300 nm laser and can go from 3 kilometers up to 10 kilometers.
1000Base-LX (IEEE 802.3z)
The implementation of 1 Gigabit Ethernet running over
multimode fiber-optic cable instead of copper twisted-pair cable, using short
wavelength laser. Multimode fiber (MMF) using 62.5- and 50-micron core; uses an
850 nanometer (nm) laser and can go up to 220 meters with 62.5-micron, 550
meters with 50-micron.
1000Base-SX (IEEE 802.3z)
Single-mode fiber that uses a 9-micron core and 1300
nm laser and can go from 3 kilometers up to 10 kilometers.
1000Base-LX (IEEE 802.3z)
is a Cisco specified
standard for Gigabit Ethernet communication. 1000BaseZX operates on ordinary
single-mode fiber-optic links with spans up to 43.5 miles (70 km)
• 1000Base-ZX (Cisco standard)
s a standard proposed by the IEEE 802.3an
committee to provide 10 Gbps connections over conventional UTP cables, (category
5e, 6, or 7 cables).
10GBase-T (802.3.an)
allows the conventional RJ45 used for Ethernet LANs and can support
signal transmission at the full 100-meter distance specified for LAN wiring.
10GBase-T
THREE TYPES OF CABLES:
Straight-through cable
• Crossover cable
• Rolled cable
e can handle speeds up to a gigabit
with a distance of up to 100 meters. Typically we’d use this cable for
100 Mbps and category 6 for a gigabit, but the category 5 Enhanced is
rated for gigabit speeds and category 6 is rated for 10 Gbp
Category 5
used to connect the following devices:
• Host to switch or hub
• Router to switch or hub
Straight -Through cable.
can be used to connect the following devices:
• Switch to switch
• Hub to hub
• Host to host
• Hub to switch
• Router direct to host
• Router to router
C
Crossover cable( Same network)
isn’t used to connect any Ethernet connections
together, you can use a rolled Ethernet cable to connect a host EIA-
TIA 232 interface to a router console serial communication (COM)
port
Rolled cable
The cable allows for very fast transmission of data, is made of glass
(or even plastic!), is very thin, and works as a waveguide to transmit
light between two ends of the fiber.
Fiber Optic
has been used to go very long distances, as in
intercontinental connections, but it is becoming more and more
popular in Ethernet LAN networks due to the fast speeds available
and because, unlike UTP, it’s immune to interference like cross-ta
Fiber optics
more expensive, has a tighter cladding, and can go
much farther distances than multimode.
Single mode
looser and has a larger core so it allows multiple light
particles to travel down the glass.
Multimode
when a host transmits data across a network to
another device, the data goes through a process and wrapped with
protocol information at each layer of the OSI mod
Encapsulation
use to communicate and exchange
information in each layer.
• Protocol data units (PDUs)
is a piece of data created and attached data field in
transport layer.
Segment
is used to get each segment to the
correct network.
Logical Addressing
adds a control header to the segment handed down from the
Transport layer.
Packet or datagram
helps us understand where things belong, how things
fit together, and what functions go where
helps summarize a complex collection of details into an
understandable model, bringing order from the chaos
Hierarchy
can help you design, implement, and
maintain a scalable, reliable, cost-effective hierarchical internetwork.
Cisco hierarchical model
literally the core of the network
Core layer
responsible for transporting large amounts of traffic
both reliably and quickly.
Core layer
is to switch traffic as fast as possible
Core layer
Don’t do in core layer:
• Never do anything to slow down traffic. This includes making sure you
don’t use access lists, perform routing between virtual local area
networks, or implement packet filtering.
• Don’t support workgroup access here.
• Avoid expanding the core (e.g., adding routers when the internetwork
grows). If performance becomes an issue in the core, give preference
to upgrades over expansion.
CCNA Routing an
sometimes referred to as the workgroup layer
and is the communication point between the access layer and the
core
Distribution Layer
are to provide routing,
filtering, and WAN access and to determine how packets can access
the core, if needed.
Distribution Layer
must determine the fastest way that network
service requests are handled—for example, how a file request is
forwarded to a server.
Distribution Layer
controls user and workgroup access to internetwork
resources. The access layer is sometimes referred to as the desktop layer.
Access Layer
sometimes referred to as the desktop layer.
Access Layer
