INDEX

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2024-02-02
2024-03-04
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Jeremy's IT Lab (Free CCNA 200-301) Day 1 - Network Devices
https://www.youtube.com/watch?v=H8W9oMNSuwo&list=PLxbwE86jKRgMpuZuLBivzlM8s2Dk5lXBQ&index=1&pp=iAQB
Client = device accessing a service. Server = device providing service
Switches allow nodes within a LAN to connect. Routers connect different LANs together

Firewalls monitor/control traffic - can be inside or outside LAN - but connected to router
Network firewalls can be hardware (e.g. firepower 2100). "Next gen" = advanced filtering
Host-based firewalls are often software

Cisco Packet Traces is a free simulation tool for network - need to log in to Cisco


Jeremy's IT Lab (Free CCNA 200-301) Day 2 - Interfaces and Cables
RJ-45 (register jack) connector is the typical end of an ethernet cable
Networks communicate at set speeds (bits/sec - Kbps) - hard drive speed measured in bytes/sec

N-Base-T = ethernet standards (e.g. 100-BASE-T = 100Mbps = 802.3u) - Baseband twisted cable
UTP (unshielded twisted pair) = 4 pairs of twisted cables
(pin config) Client: Tx=[1,2] and Rx=[3,6]. Switch: (opposite to client) Tx=[3,6] and Rx=[1,2]
Full-duplex = send and receive at the same time (using separate cables)

Routers/firewalls have same pin config as clients
Cannot connect router-router as pins line up Tx-Tx not Tx-Rx - must have compatible pin config
Straight-through cables connect pins Tx-Tx (1-1). Crossover cables connect Tx-Rx (1-3)
Most modern networks use autoMDI-X - autoconfigures Tx-Rx so works even with straight-through
Higher speed cables also use pins [4-5] and [7-8] - also bidirectional so much faster

Modern routers have ports for SFP Transceivers (can connect fiber optic cables)
UTP is much cheape rthan fiber optic but for shorter distance and leaks faint signal

In lab, can select specific cable types - consider distances between nodes for cable type


Jeremy's IT Lab (Free CCNA 200-301) Day 3 - OSI Model
7->1 is Application-Presentation-Session-Transport-Network-DataLink-Physical
Each layer down (7->1) encapsulates data and is then deencapsulated on other end (1->7)
Presentation "translated data formatting" - Session manages connections and stability
Top 3 layers are developer levels (data) - bottom 4 are infrastrucutre

Transport breaks data down into pieces - makes a segments (with L4 header)
Network (routers) set network addres info - makes a packet (with L2 header and trailer)
DataLink (switches) defines transmission methods - makes a frame (with L2 header and trailer)
Physical (cable) defines the electrical transfer of data (e.g. over copper cable) - makes bits
Data, Segment, Packet, Frame - these are all PDUs (protocol data units)

TCP/IP is the current method used - 4->1 Application-Transport-Internet-Link
So App=(app-pres-ses), Network=Internet and Link=(datalink-physical)
Layer N devices only deencapsulate up to that layer (e.g. L3 routers strip to packets)

Protocols like STP only interact on L2 - DHCP is L7 as interacts from linux userspace
	ipconfig /renew # Sends DHCP request through network


Jeremy's IT Lab (Free CCNA 200-301) Day 4  Intro to the CLI
CISCO IOS is the CLI - connect to console ports (usually USB or RJ45 - need DB9 connector)
A rollover cable (1-8, 2-7, 3-6, ...) is used to connect to console - connect over Serial
	# Defaults: Speed=9600, Databit=8, Stopbit=1, Parity=None, FlowControl=None
	Router> # Defaults to user (EXEC) mode - limited and read-only
	enable # Enables priviledged (EXEC) mode - can restart and view config but not change config
	e? # Query all possible autocomplete commands starting with "e"

	configure terminal # Enter global config mode - can do "conf t" instead
	enable password ? # Show possible arguments for "password" - "<cr>" means no more options
	enable password CCNA # Sets password to "CCNA" - now "enbale" requires a password

There are 2 config files on device: running-config (current) and startup-config (permanant)
	show running-config # Show all the commands run to set the current state
	show startup-config # Show commands to run on boot
	write # Saves running->startup (also "write memory" and "copy running-config startup-config")

	# But these logs show plaintext "enable password CCNA"
	service password-encryption # Now passwords in logs are encrypted (uses hash format 7)
	enable secret Cisco # Sets the password as "Cisco" with md5 encryption (format 5)
	no service password-encryption # Now future passwords (except secrets) are NOT encrypted 

In the lab can open up switch CLIs
	hostname R1 # Change hostname to "R1"
	do ... # Runs a command similar to "sudo"