SprintTZ Knowledge Share — Network Fundamentals: IP, Binary, Hex, MAC & OSI

lightbulbPart 1 — The Analogy

The Phone Number Analogy

Today we bridged a critical gap: how IP addressing works in the real world.

255 794 73 63 73

check_circle255 — Country Code (which country)
check_circle794 — Network Code (which carrier/region)
check_circle73 63 73 — Your phone number (you specifically)

Key Insight: This is EXACTLY how IP addressing works.

lanPart 2 — Structure

IP Address & Subnet Mask

compare_arrowsMapping

IP Address:     192.168.1.1
Subnet Mask:    255.255.255.0

┌────────────────────────────────┐
│ 192.168.1   ↔ 255 (country)   │
│ (network portion)              │
│                                │
│ .1          ↔ 73 63 73         │
│ (host portion)                 │
└────────────────────────────────┘

What This Means

check_circleFirst three octets = the network
check_circleLast octet = the host on that network

groupsPart 3 — Your Networks

Team Network Allocations

Engineer	Network	Hosts
Irene	192.168.3.0/24	254
Ibrahim	192.168.7.0/24	254
Msabi	192.168.6.0/24	254
Dennis	192.168.5.0/24	254

What /24 Means

check_circle24 bits = network portion
check_circle8 bits (32 − 24) = host addresses

Each of you manages 254 usable IPs (256 minus network and broadcast).

memoryPart 4 — Binary

Converting to Binary

The 8-Bit Byte

Bit:    7    6    5    4    3    2    1    0
Value: 128   64   32   16    8    4    2    1
      ┌────┬────┬────┬────┬────┬────┬────┬────┐
      │    │    │    │    │    │    │    │    │
      └────┴────┴────┴────┴────┴────┴────┴────┘
ON (1) → add value  |  OFF (0) → add nothing

Example: 192 to Binary

128? YES → 1  (192−128=64)
 64? YES → 1  (64−64=0)
 32? NO  → 0
 16? NO  → 0
  8? NO  → 0
  4? NO  → 0
  2? NO  → 0
  1? NO  → 0

Result: 1 1 0 0 0 0 0 0
Check:  128 + 64 = 192 ✓

grid_onPart 5 — Your Networks in Binary

Team Networks Converted

Irene

192.168.3.0/24

= 1 1 0 0 0 0 0 0  (128+64)   ✓
= 1 0 1 0 1 0 0 0  (128+32+8) ✓
= 0 0 0 0 0 0 1 1  (2+1)      ✓
= 0 0 0 0 0 0 0 0             ✓

11000000.10101000.00000011.00000000

Ibrahim

192.168.7.0/24

= 1 1 0 0 0 0 0 0  (128+64)   ✓
= 1 0 1 0 1 0 0 0  (128+32+8) ✓
= 0 0 0 0 0 1 1 1  (4+2+1)    ✓
= 0 0 0 0 0 0 0 0             ✓

11000000.10101000.00000111.00000000

Msabi

192.168.6.0/24

= 1 1 0 0 0 0 0 0  (128+64)   ✓
= 1 0 1 0 1 0 0 0  (128+32+8) ✓
= 0 0 0 0 0 1 1 0  (4+2)      ✓
= 0 0 0 0 0 0 0 0             ✓

11000000.10101000.00000110.00000000

Dennis

192.168.5.0/24

= 1 1 0 0 0 0 0 0  (128+64)   ✓
= 1 0 1 0 1 0 0 0  (128+32+8) ✓
= 0 0 0 0 0 1 0 1  (4+1)      ✓
= 0 0 0 0 0 0 0 0             ✓

11000000.10101000.00000101.00000000

The Least Significant Bit

Bit 0 (LSB) = 1    ← 2⁰ = 1
Bit 7 (MSB) = 128  ← 2⁷ = 128

192.168.5.0 = ...00000000 (OFF)
192.168.5.1 = ...00000001 (bit 0 ON)

LSB lets us count: 0,1,2,3…255

tagPart 6 — Hexadecimal

The Hexadecimal Number System

Why Do We Need Hex?

Binary is painful for humans. A MAC address in binary:

01100110 11010110 10011010 00011100 01110000 01000001

Same address in hexadecimal:

66:D6:9A:1C:70:41

Hex is shorthand for binary — every hex digit maps to exactly 4 binary bits.

The rule: Hex maps cleanly to binary. Decimal does NOT. Hex does — perfectly, every time.

Counting in Base 16

We use 0–9, then letters A–F for values 10–15:

Dec	Hex	Binary	Dec	Hex	Binary
0	0	0000	8	8	1000
1	1	0001	9	9	1001
2	2	0010	10	A	1010
3	3	0011	11	B	1011
4	4	0100	12	C	1100
5	5	0101	13	D	1101
6	6	0110	14	E	1110
7	7	0111	15	F	1111

Pattern: 1 hex digit = 4 bits. Two hex digits = 8 bits = 1 byte. MAC pairs = one byte each.

Place Values

Decimal (base 10):
  1000  100   10    1
  10³   10²   10¹   10⁰

Hex (base 16):
  4096  256   16    1
  16³   16²   16¹   16⁰

Hex → Decimal Conversions

0x66 — Dennis's first MAC byte

6 × 16 = 96
6 ×  1 =  6
         ───
Total  = 102 ✓

0xD6 — Dennis's second byte

D = 13 in decimal
13 × 16 = 208
 6 ×  1 =   6
           ───
Total   = 214 ✓

0xFF — max value of one byte

F = 15
15 × 16 = 240
15 ×  1 =  15
           ───
Total   = 255

Binary:  1111 1111
Hex:     FF
Decimal: 255
All the same number. ✓

Hex → Binary: The Direct Method

D6 hex → binary?

D = 1101
6 = 0110

D6 = 1101 0110 ← Done!
128+64+16+4+2 = 214 ✓

Decimal → Hex

Convert 192 to hex:

192 ÷ 16 = 12 remainder 0
 12 ÷ 16 =  0 remainder 12 (C)

Read bottom-up: C0
192 = 0xC0 ✓

Dennis's Full MAC Decoded

MAC: 66:D6:9A:1C:70:41

┌──────┬─────┬────────────┬──────────┐
│ Hex  │ Dec │ Binary     │ Calc     │
├──────┼─────┼────────────┼──────────┤
│  66  │ 102 │ 0110 0110  │ 6×16+6   │
│  D6  │ 214 │ 1101 0110  │ 13×16+6  │
│  9A  │ 154 │ 1001 1010  │ 9×16+10  │
│  1C  │  28 │ 0001 1100  │ 1×16+12  │
│  70  │ 112 │ 0111 0000  │ 7×16+0   │
│  41  │  65 │ 0100 0001  │ 4×16+1   │
└──────┴─────┴────────────┴──────────┘

Where You'll See Hex

Context	Example	Why Hex?
MAC	66:D6:9A:1C:70:41	6 bytes → 12 hex digits
IPv6	2001:0db8::8a2e	128 bits as hex groups
CSS Colours	#2980B9	RGB as 3 bytes
Memory	0x7FFE42A0	RAM locations
CAN Bus	0x7E8	ECU identifiers

Your brand colour: #2980B9 = R:29(41) G:80(128) B:B9(185). Blue dominates — that's why it looks blue.

Quick Reference

┌─────┬──────┬──────────┬──────────────────┐
│ Dec │ Hex  │ Binary   │ Usage            │
├─────┼──────┼──────────┼──────────────────┤
│   0 │  00  │ 00000000 │ Network address  │
│  10 │  0A  │ 00001010 │ Common host .10  │
│  15 │  0F  │ 00001111 │ Half-byte max    │
│ 127 │  7F  │ 01111111 │ Loopback 127.x   │
│ 168 │  A8  │ 10101000 │ Private .168     │
│ 192 │  C0  │ 11000000 │ Private 192.     │
│ 255 │  FF  │ 11111111 │ Broadcast/mask   │
└─────┴──────┴──────────┴──────────────────┘

fingerprintPart 7 — MAC Addresses

MAC Addresses & the MAC Table

66:D6:9A:1C:70:41

Dennis's MAC Address — 48 bits, 6 bytes in hex:

66  : D6  : 9A  : 1C  : 70  : 41
102   214   154    28   112    65

OUI: Manufacturer Fingerprint

66:D6:9A  :  1C:70:41
└── OUI ──┘  └─ Device ─┘
Manufacturer   Serial #

Scale: 281 Trillion

2⁴⁸ = 281,474,976,710,656 addresses
    = 37,000+ per person on Earth
    ~16 billion assigned so far

ARP & the MAC Table

1→ ARP: "Who has 192.168.3.10?"

2→ Switch MAC table:
   ┌────────────────┬──────────────┐
   │ MAC            │ Port         │
   ├────────────────┼──────────────┤
   │ 66:D6:9A:1C:…│ 5 (Dennis)   │
   │ AA:BB:CC:DD:…│ 3 (Irene)    │
   │ 11:22:33:44:…│ 8 (Ibrahim)  │
   │ 55:66:77:88:…│ 12 (Msabi)   │
   └────────────────┴──────────────┘

3→ Unicast to Port 3 only ✓

Layer 2 vs Layer 3

Layer	ID	Purpose
L3 Network	192.168.5.41	Route across networks
L2 Data Link	66:D6:9A:1C:70:41	Deliver on local segment

Mental model: IP = routers know where. MAC = switch knows which cable.

layersPart 8 — The OSI Model

The OSI Model — All 7 Layers

Everything today fits into one framework: Open Systems Interconnection. Seven layers — data starts at the top, travels down picking up packaging at each level, hits the wire, then unwraps in reverse at the far end.

local_shippingThe Shipping Analogy

Shipping a vase from Dar es Salaam to Kampala: write a letter (L7), put it in an addressed envelope (L3), wrap in bubble wrap (L4), put in a labelled box (L2), hand to the courier (L1). At each step, packaging is added. On arrival, unwrapped in reverse.

Memory Trick

Top-down: "All People Seem To Need Data Processing"

L7 Application      "All"
L6 Presentation     "People"
L5 Session          "Seem"
L4 Transport        "To"
L3 Network          "Need"
L2 Data Link        "Data"
L1 Physical         "Processing"

Layer by Layer

Upper Layers — Application Group

Application Layer

What the user interacts with

Network services directly to applications — web browsing, email, file transfer, DNS. Not the app itself (Chrome isn't L7), but the network protocols the app uses.

Your reality: Typing google.com triggers a DNS query (L7). SSH into a router = L7. SNMP polling = L7.

HTTP, HTTPS, DNS, DHCP, SSH, FTP, SMTP, SNMP

Presentation Layer

Translation, encryption, compression

The translator. Three jobs: format conversion (EBCDIC→ASCII), encryption (TLS/SSL), and compression.

Your reality: The padlock icon = TLS at this layer. JPEG encoding, UTF-8 character sets — all L6.

TLS/SSL, JPEG, PNG, MPEG, ASCII, Unicode

Session Layer

Managing connections

Opens, manages, and closes conversations. Handles authentication, authorisation, and session restoration.

Your reality: Website login sessions staying active for 30 min. RPC calls. NetBIOS in Windows networking.

NetBIOS, RPC, PPTP, SMB sessions, SOCKS

Lower Layers — Transport Group

Transport Layer

Reliable or fast delivery

Quality control. Breaks data into segments, numbers them, ensures correct delivery.

TCP — reliable. Three-way handshake (SYN→SYN-ACK→ACK), numbering, acknowledgements, retransmission. Web, email, file transfer.

UDP — fast. No connection, no acks. Video calls, VoIP, DNS queries, live streaming.

Port numbers identify which application receives data:

src: 192.168.5.41:54321 (Dennis)
dst: 142.250.190.14:443 (Google HTTPS)

Key ports:
22=SSH  53=DNS  80=HTTP
443=HTTPS  25=SMTP  3306=MySQL

TCP, UDP | Segment / Datagram

Network Layer

IP addressing and routing

Everything we learned about IP today. Logical addressing (IP) and routing (best path across networks). Devices: routers — your Juniper MX80, MikroTik CCR2116.

Packet header:
┌────────────┬────────────┬─────┐
│ Src IP     │ Dst IP     │ TTL │
│192.168.5.41│192.168.3.10│ 64  │
└────────────┴────────────┴─────┘

MX80: "dst 192.168.3.0/24 → ge-0/0/1"

IPv4, IPv6, ICMP, OSPF, BGP | Packet | Router

Data Link Layer

MAC addressing, local delivery

Everything about MAC addresses today. Framing, error detection (CRC), media access control. Devices: switches. Two sub-layers:

LLC (upper) → protocol multiplexing
MAC (lower) → MAC addresses, CRC, 
              media access control

Your reality: VLANs (802.1Q), STP, the MAC table exercise — all L2.

Ethernet, Wi-Fi, PPP, 802.1Q, STP | Frame | Switch

Physical Layer

Signals on the wire

Raw bits. Voltage on copper, light in fibre, radio waves for wireless. Doesn't understand addresses — only 1s and 0s.

Copper:
  Cat5e → 1G, 100m
  Cat6a → 10G, 100m
Fibre:
  SMF → long (km), laser
  MMF → short (≤550m), LED
Wireless:
  Wi-Fi 6 → 2.4/5/6 GHz, 9.6Gbps

Your reality: Crimping RJ45 = L1. SFP modules in the MX80 = L1. Link light green = L1 confirmed.

RJ45, SFP/SFP+, 802.3 physical, DSL | Bit | Hub, NIC

Data Flow Through the Stack

Dennis → Web Server:

L7 App     → HTTP GET created
L6 Present → Encrypted (TLS)
L5 Session → Session ID attached
L4 Transp  → TCP segment (port 443)
L3 Network → IP packet (src→dst)
L2 Link    → Ethernet frame (+MACs)
L1 Phys    → Electrical signals

━━━ WIRE ━━━

L1→L2→L3→L4→L5→L6→L7 (unwrap) ✓

Today's Lessons → OSI

Lesson	Layer	Why
IP Addresses	L3 Network	Logical routing
Subnets (/24)	L3 Network	Network boundaries
Binary	L1–3	Foundation of all addressing
Hexadecimal	L2–3	Compact binary for MACs, IPv6
MAC Addresses	L2 Data Link	Physical local delivery
ARP + MAC Table	L2–3	Logical → physical mapping
Cables, ports	L1 Physical	Bits on the wire

The whole picture: Today = Layers 1, 2, 3 in depth. Tomorrow = Layers 4–7 come alive when we trace a packet end-to-end. The OSI model isn't theory — it's the troubleshooting checklist: start L1 (cable plugged in?) and work up.

emoji_eventsPart 9 — Today's Wins

What We Accomplished

check_circleIP Addressing — Network + host = country code + phone number
check_circleBinary — Decimal to binary using switch logic
check_circleHexadecimal — Base-16 bridge between human and binary
check_circleSubnet Masks — /24 and host capacity
check_circleMAC Addresses — Physical identity, OUI, hex encoding
check_circleARP & MAC Tables — How switches learn and forward
check_circleOSI Model — All 7 layers mapped to today's topics

#	Pillar	Lesson
1	Binary Thinking	The native language of machines
2	Hex Shorthand	Compact notation humans can manage
3	Address Hierarchies	Organising thousands of devices
4	Uniqueness at Scale	281 trillion MACs — global order
5	Separation of Concerns	L2 and L3 solve different problems
6	Layered Architecture	OSI = universal troubleshooting

By Monday, you won't just know these. You'll own them.

rocket_launchPart 10 — What's Next

Tomorrow: Theory → Practice

check_circleSubnetting — Host ranges, broadcast, boundaries, no calculator
check_circleARP live — MAC discovery on real switches
check_circlePacket flow — All 7 OSI layers, keyboard to server and back
check_circleHex drills — Dec↔bin↔hex under time pressure
check_circleReal equipment — Switches, routers, Wireshark

assignmentHomework (Optional)

Convert teammates' networks to full binary
Convert each byte of your MAC to decimal + binary
Find your MAC: ipconfig /all (Win) · ip addr show (Linux)
Draw 7 OSI layers from memory with one protocol each
Hex challenge: decode #2980B9 → three RGB decimals

IP addresses are ZIP codes. MAC addresses are house numbers. Hex is the shorthand. Binary is the truth. The OSI model is the checklist. You've got this.

— David Emiru Egwell · SprintTZ Knowledge Share

routerPart 11 — Recovery Procedure

Flashing Juniper MX80 Router

Emergency recovery from USB (validated against Juniper emergency-boot docs):

Insert the USB emergency boot media into the MX80 front-panel USB port.
Connect a console cable and open terminal at 9600, 8, N, 1.
Reboot or power-cycle the MX80. It should boot the emergency media; if it does not, use the boot menu and select the USB device.
When prompted Do you wish to continue (y/n)?, type y.
Wait for installation to complete (can take up to ~45 minutes, depending on image and media speed).
When prompted, remove the USB emergency media and allow the router to reboot from internal storage.
At the Junos login prompt, perform initial setup from scratch or restore a saved configuration.

Important: The install process erases the current disk contents. Confirm backups and intended Junos image before proceeding.

Network Fundamentals:IP, Binary, Hex, MAC & OSI

The Phone Number Analogy

IP Address & Subnet Mask

What This Means

Team Network Allocations

What /24 Means

Converting to Binary

The 8-Bit Byte

Example: 192 to Binary

Team Networks Converted

The Least Significant Bit

The Hexadecimal Number System

Why Do We Need Hex?

Counting in Base 16

Place Values

Hex → Decimal Conversions

0x66 — Dennis's first MAC byte

0xD6 — Dennis's second byte

0xFF — max value of one byte

Hex → Binary: The Direct Method

Decimal → Hex

Dennis's Full MAC Decoded

Where You'll See Hex

Quick Reference

MAC Addresses & the MAC Table

OUI: Manufacturer Fingerprint

Scale: 281 Trillion

ARP & the MAC Table

Layer 2 vs Layer 3

The OSI Model — All 7 Layers

Memory Trick

Layer by Layer

Application Layer

Presentation Layer

Session Layer

Transport Layer

Network Layer

Data Link Layer

Physical Layer

Data Flow Through the Stack

Today's Lessons → OSI

What We Accomplished

Tomorrow: Theory → Practice

Flashing Juniper MX80 Router

Network Fundamentals:
IP, Binary, Hex, MAC & OSI