Sesson 1 Flashcards
What is a Physical Topology?
What are the 3 primary categories?
is the physical layout of devices and cabling.
BUS
STAR
MESH
How were Bus Topology connected and characteristics?
What issues did it have?
Physical cable - typically coax, terminate with vampire taps to that same cable
not scalable
communication issues
1 device at a time CMSA CD
what device was used in the middle of a star topology?
but logically how did it react?
a HUB
Logically like a bus topology
1 device can talk
SLOW with more devices
Collision domains
what type of devices are used today in star topology?
a switch
what benefits of a mesh topology
high availability through redundancy.
Full mesh - everyone connected to everyone is the most redundant. Very expenses
What is the 3 tier hierarchical model composed of?
ACCESS LAYERS -
Distribution Layer
Campus back bone
What type of devices live in the access layer of the 3 tier hierarchical model ?
what type of model of switches?
Users Phones Printers APs any other device that needs to be connected to a switch.
catalyst switches layer 2
What type of devices live in the distribution layer of the 3 tier hierarchical model ?
what type of model of switches?
this layer connects multiple access layer switches together.
example - Aggregate switch - 4500x
where is Mesh topology used in the 3 tier hierarchical model and why?
between distribution and campus back bone.
multiple paths
redundancy if a path fail
what is the design flaw in the 3 tier hierarchical model?
multiple connections from access layer to distributions layer to avoid single point of failure
What does Logical Topology mean?
Is the path that traffic will take through the network from point A to point B.
Give an example of a logical topology
2 pcs next to each other but not on the same network. Separated by a Vlan
What is a firewall?
Device that provides security by limiting traffic flows.
what is the difference of a Standalone Access point and a light weight AP?
Standalone APs
- you manage them individually
- traffic flows from end user to AP to end user
light weight AP
1. requires a WLC - wireless lan controller (central location)
traffic flows from end user to AP to WLC to AP to end user.
what is the OSI Model?
- Physical
- Data link
- Network
- Transport
- Session
- Presentation
- Application
What is ATIL model? (TCP/IP)
Applications
Transport
Internet
Link
Explain what happens in the Application layer
all the services behind the scene that allow the application to work
Switches make their decision based on what layer?
Layer 2 (data link) or Link (tcp/ip model)
what is the name of the payload (PDU) when it is at the transport layer
Segment
what is the name of the payload (PDU) when it is at network/internter layer ?
Packet
what is the name of the payload (PDU) when it is at the link layer?
Frame
what is the name of the payload (PDU) when it is at the application layer?
Data
what is the name of the payload (PDU) when it is at the physical layer?
Bits
Examples of physical devices?
Nics, cables, MTU, bits, fiber optic, copper cable
max distance for RJ45 cable?
100 meters or 328 feet
what is the wire standard for straight cable
1 - green/white 2 - green 3 - yellow/white 4 - Blue 5 - Blue/white 6 - yellow 7 - Brown/white 8 - Brown
what is the standard for a cross over cable
pin 1 goes to pin 3
pin 2 goes to pin 6
when do you use straight through cables and when you use cross over cable -
straight through cable - when connecting unlike devices togother (Pc to switch)
cross over cable - when connecting like devices (switch to switch)
what is auto MDIX
devices changes a straight through cable transmission and receive pins so it can work…
characteristics of Multi mode fiber optic
LED base / can send multiple signals down the wire / alot of bounces
shorter distances
shorter bandwidth
cheaper
characteristic of Single fiber mode optic
laser base
Long distances
High bandwidth
what is important for layer 2 operation
Frame Encapsulation Switches work in this layer MAC address are used here HDLC PPP
What is the min/max a ethernet frame can be transfered?
46 - Mininum transfer unit
1500 Max transfer unit
what is FCS (frame check sequence)
a mathematical calculation that the source creates and when the destination device reads it and gets the same # that means that the frame has not be modified.
What is a MAC address
unique # that identifies a device on layer 2 or also known LAN Broadcast Domain Subnet Vlan
What is ARP?
Address Resolution Protocol
ARP is a layer 3 to layer 2 mapping
An example of a broadcast traffic
Request are only sent within a vlan
Local devices create a arp cache
what is the command to enter the arp cache?
arp -a
what is important in layer 3/internet layer?
Packet encapsulation
Routing
IP addressing (IPv4 and IPv6)
what is Service type mean in layer 3 packet?
allows us to differentiate what packets gets done first.
Example - youtube video vs VoIP call
VoIP calls will get a higher service (QOS) than the youtube stream.
what is TTL used for in packet header?
it is the max life span of a packet. Its expiration hop count.
Prevents a packet from lasting forever.
prevents loops on the network
what message is back to the PC when TTL expires?
ICMP TTL exceeded message
what does protocol field in a layer 3 packet mean
indicates what is happening on the transport layer - TCP or UDP
What is the list of importants in a packet layer 3 header
- Source/Dest IP address
- TTL
- Protocol
- Service Type
What are the benefits of TCP connection?
Transmission control protocol
Provides flow control and error checking
Allow for access to the network layer
Ensures packet sequencing and reliable delivery
connection oriented
Sequence number in network segment is good for?
keeps track of each segment.
What is windowing?
is a 3 way handshake
SYN
SYN - ACK
ACK
What is window size?
is the amount of bytes that can be sent at a time for a segment.
If there is not issues transferring, window size will grow. and reduce if there is a problem.
