CompTIA Network+ certification course sum up. Oriented for cybersecurity later courses. *This sheet is quite simplified as its goal is to prepare for cybersecurity certifications. Some purely tech topics are missing.*
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Basic elements
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Layer 1, contention-based (unorderly transmission)
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CSMA/CD
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Carrier Sense Multiple Access / Collision Detect
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Carrier Sense
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Listen to the wire, verify if busy
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Multiple Access
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all devices have access at any time
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Collision Detect
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if collision occurs, wait random time, try again
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Collision Domain /CDO
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all devices on an internet segment (same cable or hub)
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half duplex, operates CSMA/CD
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Switches
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creates multiple CDOs, 1port=1CDO
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-> no chance of collision, full-duplex capability
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SPEED
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Ethernet
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10Mbps
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Fast Ethernet
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100Mbps
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Gigabit Ethernet
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1000Mbps / 1Gbps
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10-Gigabit Ethernet
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10Gbps
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100-Gigabit Ethernet
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100Gbps
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DISTANCE (memo)
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Copper
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100m
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CAT6
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100m@1Gbps / 55m@10Gbps
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CAT8
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30m
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MMF (T, TX,FX, SR, SX)
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short range (200-500m)
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SMF (LX, LR, ZX)
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long range (in km)
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Collision domain /CD
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network segment where packets collide. Collision detection/avoidance can be set
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Broadcase domain /BD
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domain where broadcast packets are diffused. The smaller the better
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Hub
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multiport repeater with or without amplification (passive/active/smart)
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Bridge
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analyse source MAC adr & populates table. Separates collision domains
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Switch
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combination of hub and bridge
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- layer 2
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all ports belong to broadcast domain
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- layer 3
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creates one BD per port. Makes routing decisions, interconnect entire NW
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Router
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connects NW together, makes fw decisions. Separates CD and BD
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Link Aggregation
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802.3ad
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combines multiple connect° into a single logical connect°
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increased bandwith, congestion lowered
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PoE, PoE+
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802.3af/at
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electrical power over Ethernet, Cat5 mini, 15.4W/25.5W
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Port monitoring
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network sniffer plugged on a hub - analyse purpose
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Port mirroring
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copy all traffic to another port
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User Auth.
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802.1x
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once auth., a key is generated and shared
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Management
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SSH for remote access, console port for local admin.
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Out-of-Band
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NW conf. devices on a separate NW
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First-Hop Redundancy
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creates a stand-by router in case the active router fails
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MAC Filtering
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filters connect° based on MAC adr
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Traffic Filtering
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filters connect° based on IP adr
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QoS
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forwards traffic according to priority markings
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Role
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redundant links btw switches, prevent traffic loops. Without STP, MAC table can be corrupted
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Broadcast Storms
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when a switches broadcasts btw each other in loop. Multiple copies are forwarded in loop. NW becomes saturated
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Root Bridge
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reference bridge for spanning tree. defined with BID (lower BID) - made of priority value and MAC adr.
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Non-Root Bridge
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all other switches
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Root Port
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on N-RB, closest port to the RB
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Designated Port
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port with the lowest cost index to route to the RB. RB has only designated ports
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Non-Des. Port
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all other ports. Block traffic to avoid loops
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Port states
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- Blocking
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BPDU recieved but not forwarded
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- Listensing
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idem+ but populates MAC adr table
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- Learning
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process BPDU, switch tries to determine its role
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- Forwarding
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full ops
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Link Costs
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speed of a link. Lower the speed, higher the cost
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ex:
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Fast Ethernet :19, GB Ethernet : 4
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Long STP from 2.000.000 to 2.
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Principle
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allows different logical NWs with a single hardware.
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How ?
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use certain ports to separate broadcast domains
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VLAN Trunking
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multiple VLAN using same phy. cable
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TPI
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Tag Protocol Identifier
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TCI
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Tag Control Identifier
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VLAN 0
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Native VLAN left untagged
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VPN
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virtual tunnel over untrusted NW/Internet
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VPN concentrator
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tunnel traffic to a single location
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VPN headend
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Firewalls
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softw or hardw, allows some outcome traffic, blocks some inbound traffic
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NGFW
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packet inspection at layer 7 (App lvl). much more powerful
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IDS/IPS
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Intrusion Detection/Prevention System
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recognizes attacks and can respond
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Proxy
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content filter server
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Content/Caching Engine
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caching service for a proxy
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Load Balancer
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distributes request across a server farm
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