bc is a nice calculator that one can use under linux terminal.

a good exercise: count from 0 to 255 and convert it to binary

```# install
# debian/ubuntu
apt install bc
# fedora/redhat/centos
yum install bc
# run
bc
# let's count from 1 to 255 and use bc to convert it to binary
bc 1.06.95
Copyright 1991-1994, 1997, 1998, 2000, 2004, 2006 Free Software Foundation, Inc.
This is free software with ABSOLUTELY NO WARRANTY.
For details type `warranty'.
scale=5
# calculate the maximum decimal possible value with 8 binary bits (two to the power of 8 = 8 binary digits)
2^8
256
obase=2; 0
0
# value of digit 1 is 1
obase=2; 1
1
# value of digit 2 is 2
obase=2; 2
10
obase=2; 3
11
value of digit 3 is 4
obase=2; 4
100
obase=2; 5
101
obase=2; 6
110
obase=2; 7
111
# value of digit 4 is 8
obase=2; 8
1000
obase=2; 9
1001
obase=2; 10
1010
obase=2; 11
1011
obase=2; 12
1100
obase=2; 13
1101
obase=2; 14
1110
obase=2; 15
1111
# value of digit 5 is 16
obase=2; 16
10000
obase=2; 17
10001
obase=2; 18
10010
obase=2; 19
10011
obase=2; 20
10100
obase=2; 21
10101
obase=2; 22
10110
obase=2; 23
10111
obase=2; 24
11000
obase=2; 25
11001
obase=2; 26
11010
obase=2; 27
11011
obase=2; 28
11100
obase=2; 29
11101
obase=2; 30
11110
obase=2; 31
11111
# value of digit 6 is 32
obase=2; 32
100000
obase=2; 33
100001
obase=2; 34
100010
obase=2; 35
100011
obase=2; 36
100100
obase=2; 37
100101
obase=2; 38
100110
obase=2; 39
100111
obase=2; 40
101000
obase=2; 41
101001
obase=2; 42
101010
obase=2; 43
101011
obase=2; 44
101100
obase=2; 45
101101
obase=2; 46
101110
obase=2; 47
101111
obase=2; 48
110000
obase=2; 49
110001
obase=2; 50
110010
obase=2; 51
110011
obase=2; 52
110100
obase=2; 53
110101
obase=2; 54
110110
obase=2; 55
110111
obase=2; 56
111000
obase=2; 57
111001
obase=2; 58
111010
obase=2; 59
111011
obase=2; 60
111100
obase=2; 61
111101
obase=2; 62
111110
obase=2; 63
111111
# value of digit 7 is 64
obase=2; 64
1000000
obase=2; 65
1000001
obase=2; 66
1000010
obase=2; 67
1000011
obase=2; 68
1000100
obase=2; 69
1000101
obase=2; 70
1000110
obase=2; 71
1000111
obase=2; 72
1001000
obase=2; 73
1001001
obase=2; 74
1001010
obase=2; 75
1001011
obase=2; 76
1001100
obase=2; 77
1001101
obase=2; 78
1001110
obase=2; 79
1001111
obase=2; 80
1010000
obase=2; 81
1010001
obase=2; 82
1010010
obase=2; 83
1010011
obase=2; 84
1010100
obase=2; 85
1010101
obase=2; 86
1010110
obase=2; 87
1010111
obase=2; 88
1011000
obase=2; 89
1011001
obase=2; 90
1011010
obase=2; 91
1011011
obase=2; 92
1011100
obase=2; 93
1011101
obase=2; 94
1011110
obase=2; 95
1011111
obase=2; 96
1100000
obase=2; 97
1100001
obase=2; 98
1100010
obase=2; 99
1100011
obase=2; 100
1100100
obase=2; 101
1100101
obase=2; 102
1100110
obase=2; 103
1100111
obase=2; 104
1101000
obase=2; 105
1101001
obase=2; 106
1101010
obase=2; 107
1101011
obase=2; 108
1101100
obase=2; 109
1101101
obase=2; 110
1101110
obase=2; 111
1101111
obase=2; 112
1110000
obase=2; 113
1110001
obase=2; 114
1110010
obase=2; 115
1110011
obase=2; 116
1110100
obase=2; 117
1110101
obase=2; 118
1110110
obase=2; 119
1110111
obase=2; 120
1111000
obase=2; 121
1111001
obase=2; 122
1111010
obase=2; 123
1111011
obase=2; 124
1111100
obase=2; 125
1111101
obase=2; 126
1111110
obase=2; 127
1111111
# value of digit 8 is 128
obase=2; 128
10000000
obase=2; 129
10000001
obase=2; 130
10000010
obase=2; 131
10000011
obase=2; 132
10000100
obase=2; 133
10000101
obase=2; 134
10000110
obase=2; 135
10000111
obase=2; 136
10001000
obase=2; 137
10001001
obase=2; 138
10001010
obase=2; 139
10001011
obase=2; 140
10001100
obase=2; 141
10001101
obase=2; 142
10001110
obase=2; 143
10001111
obase=2; 144
10010000
obase=2; 145
10010001
obase=2; 146
10010010
obase=2; 147
10010011
obase=2; 148
10010100
obase=2; 149
10010101
obase=2; 150
10010110
obase=2; 151
10010111
obase=2; 152
10011000
obase=2; 153
10011001
obase=2; 154
10011010
obase=2; 155
10011011
obase=2; 156
10011100
obase=2; 157
10011101
obase=2; 158
10011110
obase=2; 159
10011111
obase=2; 160
10100000
obase=2; 161
10100001
obase=2; 162
10100010
obase=2; 163
10100011
obase=2; 164
10100100
obase=2; 165
10100101
obase=2; 166
10100110
obase=2; 167
10100111
obase=2; 168
10101000
obase=2; 169
10101001
obase=2; 170
10101010
obase=2; 171
10101011
obase=2; 172
10101100
obase=2; 173
10101101
obase=2; 174
10101110
obase=2; 175
10101111
obase=2; 176
10110000
obase=2; 177
10110001
obase=2; 178
10110010
obase=2; 179
10110011
obase=2; 180
10110100
obase=2; 181
10110101
obase=2; 182
10110110
obase=2; 183
10110111
obase=2; 184
10111000
obase=2; 185
10111001
obase=2; 186
10111010
obase=2; 187
10111011
obase=2; 188
10111100
obase=2; 189
10111101
obase=2; 190
10111110
obase=2; 191
10111111
obase=2; 191
10111111
obase=2; 192
11000000
obase=2; 193
11000001
obase=2; 194
11000010
obase=2; 195
11000011
obase=2; 196
11000100
obase=2; 197
11000101
obase=2; 198
11000110
obase=2; 199
11000111
obase=2; 200
11001000
obase=2; 201
11001001
obase=2; 202
11001010
obase=2; 203
11001011
obase=2; 204
11001100
obase=2; 205
11001101
obase=2; 206
11001110
obase=2; 207
11001111
obase=2; 208
11010000
obase=2; 209
11010001
obase=2; 210
11010010
obase=2; 211
11010011
obase=2; 212
11010100
obase=2; 213
11010101
obase=2; 214
11010110
obase=2; 215
11010111
obase=2; 216
11011000
obase=2; 217
11011001
obase=2; 218
11011010
obase=2; 219
11011011
obase=2; 220
11011100
obase=2; 221
11011101
obase=2; 222
11011110
obase=2; 223
11011111
obase=2; 224
11100000
obase=2; 225
11100001
obase=2; 226
11100010
obase=2; 227
11100011
obase=2; 228
11100100
obase=2; 229
11100101
obase=2; 230
11100110
obase=2; 231
11100111
obase=2; 232
11101000
obase=2; 233
11101001
obase=2; 234
11101010
obase=2; 235
11101011
obase=2; 236
11101100
obase=2; 237
11101101
obase=2; 238
11101110
obase=2; 239
11101111
obase=2; 240
11110000
obase=2; 241
11110001
obase=2; 242
11110010
obase=2; 243
11110011
obase=2; 244
11110100
obase=2; 245
11110101
obase=2; 246
11110110
obase=2; 247
11110111
obase=2; 248
11111000
obase=2; 249
11111001
obase=2; 250
11111010
obase=2; 251
11111011
obase=2; 252
11111100
obase=2; 253
11111101
obase=2; 254
11111110
# this is the maximum decimal value of a 8 bit (1Byte) integer
# why 255 and not 256?
# because 256 is the value of the 9th digit
obase=2; 255
11111111
# maximum value of all 8 binary (1x Byte) digits: 128+64+32+16+8+4+2+1 = 255

```

# networking hardware and cables:

150m of LWL-patch cable LC UPC to LC UPC Duplex plug OM2 Multimode PVC (OFNR) 2.0mm fibre optic data cable https://www.fs.com/de/products/74394.html

interconnecting two 48x ports 1Gbit switches cisco 200-50GS switch with fibre gbic Transceiver Modul mit DOM – Cisco GLC-SX-MM Kompatibles 1000BASE-SX SFP 850nm 550m – https://www.fs.com/de/products/11774.html

# ip net calculator:

now how do routers and computers calculate routes and subnets?

http://jodies.de/ipcalc

for ipv6

# network classes:

https://en.wikipedia.org/wiki/Classful_network

# network planning tools:

https://www.cbtnuggets.com/blog/career/career-progression/5-best-network-simulators-for-cisco-exams-ccna-ccnp-and-ccie

https://www.solarwinds.com/free-tools/gns3-network-emulator

Network monitoring software

https://www.solarwinds.com/network-performance-monitor/registration

designed to reduce network outages and improve performance

• Multi-vendor network monitoring
• Critical path visualization with NetPath
Starts at 2.440 €

# computer network schematics:

seems there are no standardized symbols… this is one possible (cisco) representation: (one can download high res network symbols from cisco)

cisco symbol for:

• file-server
• web server:
• micro web server:
• gigabit switch router
• androgynous person

# drawing tools:

http://dia-installer.de/index.html

# certificates and exercises:

https://www.quora.com/What-are-some-of-the-best-resources-to-learn-Cisco-Packet-Tracer

http://www.ciscopress.com/articles/article.asp?p=2180208&seqNum=9

# security:

after all switches and routers are computers: https://www.bleepingcomputer.com/news/security/cisco-warns-of-public-exploit-code-for-critical-switch-flaws/