CCNA Flashcards
List the 7 layers of the OSI model
Application Presentation Session Transport Network Data Link Physical
List the 4 layers of the TCP\IP model, and what layers correspond to the OSI model
Application (Application, Presentation, Session)
Transport (Transport)
Internet (Network)
Link (Link)
What is SFP?
Small Form Factor Plug-able Transceiver
What are the two interaction types?
Same Layer Interaction
Adjacent Layer Interaction
What layer does Process to Process occur?
Data exchanged from Application to Application layer
What layer does Host to Host occur?
Data exchanged from Transport to Transport layer
STP and layer
Spanning Tree Protocol (layer 2)
OSPF and layer
Open Shortest Path First (layer 3)
What are the 2 configs
Startup-config
Running-config
What are 3 commands to write to startup-config?
and what mode can they be run from?
write
write memory
copy running-config startup-config
‘privilege exec’ mode
What are the 4 modes and indicator
user exec mode - >
privileged exec mode - #
global config - (config)#
interface configuration mode - (config-if)#
UTP
Un-shielded Twisted Pair
Draw RJ45 wiring diagram:
Straight Through
Cross over
Roll over
10 Base-T, 100 Base-T uses 4 pins\wires
1000 Base-T, 10G Base-T uses 8 pins\wires
Straight Through: 1 1 2 2 3 3 4 4 only 1000 base-t 5 5 only 1000 base-t 6 6 7 7 only 1000 base-t 8 8 only 1000 base-t
Crossover: 1 3 2 6 3 1 4 4 only 1000 base-t 5 5 only 1000 base-t 6 2 7 7 only 1000 base-t 8 8 only 1000 base-t
Rollover: 1 8 2 7 3 6 4 5 5 4 6 3 7 2 8 1
Draw data moving through the OSI model with headers and names of PDUs
OSI Model Protocol Data Units
Application
Presentation
Session Data Data
Transport Data | L4 Segment
Network Data | L4 | L3 Packet
Data Link L2 | Data | L4 | L3 | L2 Frame
Physical 1 \ 0 Bits
Cisco Blue cable is called
Roll over cable
List the Cisco default connection parameters:
Baud 9600 Data bits 8 Stop Bits 1 Parity None Flow Control None
List devices are RJ45 pinned the same, and ones different.
Same: PC\Server\Firewall\Router
Different: Switch
What does ‘Bad Secrets’ mean
invalid password
Command to get from ‘user exec’ mode to ‘privileged exec’ mode
enable
Command to get from ‘privileged exec’ mode to ‘Global Configuration’ mode
Configure Terminal
conf t
Commands to protect ‘privilege exec’ mode with password
enable password
enable secret
Command to list contents of a file
show
Command to run commands in other modes
Do
List numbers and types of encryption for passwords
7 Cisco propitiatory encryption (not secure)
5 MD5 encryption
Which of the 2 takes precedent:
enable password
enable secret
enable secret
Command to encrypt password
service password-encryption
Command to execute a command
run
command to remove a command
no
Command to name a device
hostname
UTP cables pins
Transmit
Receive
for Router Firewall Switch and PC
Device Transmit Receive
Router 1,2 3,6
Firewall 1,2 3,6
PC 1,2 3,6
Switch 3,6 1,2
List 2 modes of fiber optic
Single Mode
Multi Mode
List physical layers of fiber optic
Fiberglass core
cladding reflects light
protective buffer
outer jacket
Describe differences between single mode and multi mode
single-mode multimode
narrower wider core diameter
single angle multiple angles
longer than UTP and MM longer than UTP but shorter than SM
more $$ than UTP and MM cheaper than SM, more $$ than UTP
laser based LED based
Name standard for fiber optic
802.3
list max length for:
single mode
Multimode
UTP
single mode: 5/10/30 km
Multimode: 500 m
UTP 100 m
explain physical layer
physical characteristics: pins, voltages, cables, plugs
data converted to electrical or radio signals
explain data link layer
node-to-node connectivity and data transfer
PC to switch, switch to router, router to router
defines how data is formatted over phy
detects and corrects physical layer errors
uses layer 2 addressing
routers are used to?
connect separate lans
how do switched define lans
multiple switches connected to each other expand a lan
multiple switches connected to a router but not each other define separate LANs.
PDU
Protocol Data Units
Name 5 fields in Ethernet Frame Header and what they are used for.
Preamble - used to sync
SFD (start frame delimiter) - used to sync
Destination - layer 2 destination address
Source - layer 2 source address
Type - layer 3 protocol used in packet (usually IPv4/IPv6) or Length field
SFD
Start Frame Delimiter
Name fields in Ethernet Frame Trailer, and purpose
FCS (Frame Check Sequence) - used for error checking
Describe Preamble and SFD Fields of an Ethernet Frame
Preamble: SFD (Start Frame Delimiter)
7 bytes 1 byte
10101010 * 7 10101011
clock sync marks end of preamble and beginning of rest of frame
Describe Source and Destination fields of an Ethernet Frame and size
provides MAC address of sending and receiving devices
6 bytes/48 bit
How long is a MAC address
6 bytes/48 bits
Describe Type/Length field of an Ethernet Frame
2 bytes/16 bit can represent Type or Length 1500 or less indicates Length 1536 or greater indicates Type IPv4 = 0x0800 20248 ARP = 0x0806 IPv6 = 0x86DD 34525
Describe FCS field, acronym, size, CRC
FCS - Frame Check Sequence
4 bytes/32 bit
detects corruption with CRC
BIA
Burned in Address
AKA MAC address
Describe MAC address bytes
First 3 - OUI - Organizationally Unique Identifier
Last 3 - unique to device itself
written as 12 hex characters
OUI
Organizationally Unique Identifier
On a network diagram what does F mean
Fast Ethernet
On a network diagram what does G mean
Gigabit
what is unicast
sent to one address
what is multicast
sent to multiple address
what is it called when a switch learns an address
dynamically learned MAC address or
dynamic MAC address
What is a Unknown Unicast Frame, and what happes
MAC not in switch table (MAC\interface)
Frame is FLOODed across all ports except source
What is a Known Unicast Frame
MAC is in switch table (MAC\interface)
Frame is FORWARDed to only port in switch table
Are Dynamic MAC addresses permanent
No. Removed after 5 minutes.
What 2 fields are not considered part of the ethernet fram
Preamble
SFD - Start Frame Delimiter
What size is the Ethernet Header and Trailer combined
7 not counted
1 not counted
6 + 6 + 2 + 4 = 18 bytes
What size is the minimum size of an Ethernet frame
Header + Payload (Packet) + Trailer = 64 bytes
64 bytes - 18 bytes (header and trailer) = 46 bytes
46 bytes
ARP, what it does, and what it’s messages are
Address Resolution Protocol
Used to discover the Layer 2 address of a known Layer 3 address
ARP Request - is a broadcast
ARP Reply - is a unicast
What is the broadcast MAC address
FFFF.FFFF.FFFF
what is the arp command (for OSs) and what is listed?
Windows\MacOS\Linux: arp -a
Cisco: show arp (in privileged exec mode)
internet address, physical address, and type
What is ping, and what does it measure, and messages
network utility to test reachability
measures round trip time
ICMP Echo Request
ICMP Echo Reply
default # of pings, size, and reply
windows:
4 pings
32 bytes
sent/received/lost
cisco: 5 pings 100 bytes ! = successful . = failed min/avg/max of successful pings
Command to show MAC address table on Cisco?
what are the outputs?
show mac address-table vlan MAC address type ports
what is it called when dynamic entries are dropped from a MAC table
aging
what is cisco command to clear all dynamic MAC addresses from table
clear mac address-table dynamic
what is cisco command to clear a single dynamic MAC addresses from table
clear mac address-table dynamic address 0000.0000.0001
what is cisco command to clear dynamic MAC addresses from table for a single interface
clear mac address-table dynamic interface G0\0
IP addresses are how many bit/bytes long?
32 bits/4 bytes
list the IP4 address classes table
Class First octet First octet numerica range
a 0 0-127 (126) /8
b 10 128-191 /16
c 110 192-223 /24
d 1110 224-239 multicast
e 1111 240-255 reserved experimental
what is loopback address?
and what is it used for?
127.0.0.0 - 127.255.255.255
used to test the network stack. (OSI & TCP\IP models)
write the netmask table for the first 3 classes and both forms of notation
a /8 255.0.0.0
b /16 255.255.0.0
c /24 255.255.255.0
Cisco router command to show interfaces?
List columns.
show ip interface brief Interface - name IP-address - dotted decimal ok? - ignore legacy method - manual\unset status - Layer 1 status protocol - Layer 2 status
cisco command to configure interface?
mode required?
cli prompt?
global config mode
interface gigabitethernet 0/0
(config-if)#
cisco command to set ip address for an interface
ip address 10.255.255.254 255.0.0.0
cisco command to enable an interface
no shutdown
cisco command to get info on interface
show interfaces
show interfaces g0/0
cisco command to list optional interface info?
list columns?
show interfaces description interface status protocol description
cisco command to set optional interface info?
interface g0/0
description ## to SW1 ##
what is the default configuration of a cisco router interface?
what is the default configuration of a cisco switch iinterface?
router: shutdown/administratively down
switch: no shutdown
cisco command to list details about interface?
list columns.
show interfaces status Port Name Status VLAN Duplex Speed Type
what are commands to set duplex and speed?
duplex
speed
cisco command to configure more than one interface?
interface range f0/5 - 12
interface range f0/5 - 6, f0/9 - 12
description
shutdown
CSMA/CD
Carrier Sense Multiple Access with Collision Detection
What layer does a Hub operate?
Layer 1
What layer does a Hub operate?
Layer 1
What is a collision domain
All devices attached to a hub where messages collide and are not received.
what happens if a switch is set to auto-negotiate,
and a host is set to less than Speed:1000 Mbps and duplex:Full?
There will be a Duplex mismatch and collisions will occur.
Runts counter
Counts frames that are smaller than minimum frame size - 64 bytes
Giants counter
Counts frames that are larger than maximum frame size - 1518 bytes
CRC counter
Counts frames that failed CRC check
frame counter
Counts frames that have an incorrect format
input error counter
list counters
Counts frames from: runts counter Giants counter CRC counter Frame counter
Output counter
Counts frames that switch tried to send, but failed due to an error.
IPv4 Header field - Version
Version - identifies version on IP used - 4 or 6
IPv4 Header field - IHL
Internet Header Length in 4 bytes increments
20 to 60 bytes
IPv4 Header field - DSCP
Differentiated Services Code Point
used for QoS
IPv4 Header field - ECN
Explicit Congestion Notification
Optional feature that requires both endpoints as well as infrastructure to support it
IPv4 Header field - Total Length
Indicates the total length of the packet
(L3 header + layer 4 segment)
in bytes
minimum 20 - 65,535 max
IPv4 Header field - Identification
used to identify which packet the fragment belongs to
packets are fragmented if larger than the MTU (maximum Transmission unit)
fragments are reassembled by the receiving host
MTU and size
Maximum Transmission Unit
1500 bytes
IPv4 Header field - Flags
used to control/identify fragments Bit 0: Reserved, always set to 0 Bit 1: Don't fragment (DF bit), used to indicate a packet that shouldn't be fragmented. Bit 2: More Fragments (MF bit) - set to 1 if there are more fragments set to 0 for last fragment
IPv4 Header field - Fragment Offset
13 bits
used to indicate position in un-fragmented packet
Allows fragmented packs to be reassembled when arriving out of order.
IPv4 Header field - TTL
Time to Live
router will drop packets with TTL of 0
prevents infinite loops
originally in seconds, now in hops
IPv4 Header field - Protocol
indicates protocol
6: TCP
17: UDP
1: ICMP
89: OSPF
ICMP
Internet Control Message Protocol
IPv4 Header field - Header Checksum
a calculated checksum used to check for errors in the IPv4 header
IPv4 Header field - Options
rarely used. If IHL field > 5, then options are present
what is one way reachability
when router has only one way in route table
what is ‘most specific matching’ route
longest prefix length
/32 > /24 > /16 > /8 > /0
Name the route types on a routing table
Static - manually configured
Connected - represent network that local address is part of
Local - exact address configured on interface
command to configure default route
ip route
CIDR
Classless Inter-Domain Routing
IANA
Internet Assigned Numbers Authority
PTP
Point To Point
IETF
Internet Engineering Task Force
Draw table for CIDR /24 thru /32 with number of hosts
/24 256 -2 = 254
/25 128 -2 = 126
can /31 be used?
Yes. Only for point to point networks.
/31 = 2 - 2 = 0 usable hosts
but still works for point to point.
can /32 be used?
Yes.
Can be used to create a static route to one specific host.
VLSM
Variable Length Subnet Masks
FLSM
Fixed Length Subnet Masks`
VLSM steps?
Largest first
next largest next
and so on and so on