add brouillon subnetting
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shango-wk
@@ -22,3 +22,4 @@ tags:
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[[Routing Fundamentals]]
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[[Static Routing]]
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[[The Life of a Packet]]
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[[Subnetting (Part 1)]]
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@@ -1,8 +1,8 @@
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---
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id: 07. IPv4 Addressing (Part 1)
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aliases: []
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tags:
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- CCNA
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tags:
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- CCNA
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---
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# IPv4 Addressing (Part 1)
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@@ -37,13 +37,13 @@ Class C
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## [[IPV4]] address classes
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| Class |First octet | numeric range| Prefix Length |
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| ----- | ---------- | --------------| /8 |
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| A |0xxxxxxxx | 0-127 | /16 |
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| B |10xxxxxxx | 128-191 | /24 |
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| C |110xxxxxx | 192-223 | |
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| D |1110xxxxx | 224-239 | |
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| E |1111xxxxx | 240-255 | |
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| Class |First octet | numeric range | Prefix Length |
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| ----- | ---------- | ------------- |------------- |
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| A |0xxxxxxxx | 0-127 | /8 |
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| B |10xxxxxxx | 128-191 | /16 |
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| C |110xxxxxx | 192-223 | /24 |
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| D |1110xxxxx | 224-239 | |
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| E |1111xxxxx | 240-255 | |
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class D are reserverd for Multicast addresses
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194
13. Subnetting (Part 1).md
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194
13. Subnetting (Part 1).md
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@@ -0,0 +1,194 @@
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---
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id: 1777840095-WYOD
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aliases:
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- Subnetting (Part 1)
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tags:
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- CCNA
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---
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# Subnetting (Part 1)
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## IPV4 Address Classes
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| Class |First octet | numeric range | Prefix Length |
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| ----- | ---------- | ------------- |------------- |
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| A |0xxxxxxxx | 0-127 | /8 |
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| B |10xxxxxxx | 128-191 | /16 |
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| C |110xxxxxx | 192-223 | /24 |
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| D |1110xxxxx | 224-239 | |
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| E |1111xxxxx | 240-255 | |
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### Maximum Hosts per Network
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Host portion all 0s = Network address (network ID)
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Host portion all 1s = broadcast address
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192.168.1.0/24 -> 192.168.1.255/24
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Host portion = 8 bits = 2^8 = 256
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Maximum hosts per network = 2^8-2 = 254
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172.16.0.0/16 -> 172.16.255.255/16
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Host portion = 16 bits = 2^16 = 65,536
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Maximum hosts per network = 2^16 -2 = 254
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10.0.0.0/8 -> 10.255.255.255/8
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Host portion = 24 bits = 2^24 = 16,777,216
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Maximum hosts per network = 2^24 -2 = 16,777,214
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### How IP addresses are distrubuted
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- The [[IANA]] (Internet Assigned Numbers Authority) assigns IPV4 addresses/networks to
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companies based on their size
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- For example, a very large company might receive a class A or class B network, while a small
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company might receive a ckass C network.
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- However, this led to many wasted IP addresses.
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#### Example 1
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+----+ +----+
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| R1 |<----->| R2 |
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+----+ ^ +----+
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Point to Point network
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- 256 addresses
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- 1 network address (203.0.113.0)
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- 1 broadcast address (203.0.113.255)
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- 1 R1 address (203.0.113.1)
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- 1 R2 address (203.0.113.2)
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- **252 addresses Wasted**
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#### Example 2
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Company X needs IP addressing for 5000 end hosts.
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- A class C network does not provide enough addresses, so a class B network must be assigned
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- This will result in about 6000 addresses being wasted.
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## CIDR
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- When the internet was first created, the creators did not predict that the internet
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would become as large as it is today
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- This resulted in wasted address space like the examples.
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- The [[IETF]] introduced [[CIDR]] in 1993 to replace the 'classful' addressing system.
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- With CIDR, the requirement of ...
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- Class A = /8
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- Class B = /16
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- Class C = /24
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were removed
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- This allowed larger networks to be split into smaller networks, allowing greater efficiency
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- These smaller networks are called 'subnetworks' or [[subnetting]]
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+----+ +----+
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| R1 |<----->| R2 |
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+----+ ^ +----+
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203.0.113.0/24
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Network address
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11001011.00000000.01110001.*00000000*
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203 . 0 . 113 . 0
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Subnet Mask
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11111111.11111111.11111111.*00000000*
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255 . 255 . 255 . 0
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2^8 - 2 = 254 usable addresses.
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How many usable addreses are there in each network?
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#### CIDR /25
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**203.0.113.0/25**
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Network address:
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11001011.00000000.01110001.0*0000000*
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203 . 0 . 113 . 0
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Subnet Mask
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11111111.11111111.11111111.1*0000000*
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255 . 255 . 255 . 128
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*2^7 - 2 = 126 usable addresses*
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#### CIDR /26
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**203.0.113.0/26**
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Network address
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11001011.00000000.01110001.00*000000*
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203 . 0 . 113 . 0
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Subnet Mask
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11111111.11111111.11111111.11*000000*
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255 . 255 . 255 . 192
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*2^6 - 2 = 62 usable addresses*
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#### CIDR /27
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**203.0.113.0/27**
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Network address
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11001011.00000000.01110001.00*000000*
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203 . 0 . 113 . 0
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Subnet Mask
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11111111.11111111.11111111.111*00000*
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255 . 255 . 255 . 224
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*2^5 - 2 = 30 usable addresses*
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#### CIDR /28
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**203.0.113.0/28**
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Network address
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11001011.00000000.01110001.00*000000*
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203 . 0 . 113 . 0
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Subnet Mask
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11111111.11111111.11111111.1111*0000*
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255 . 255 . 255 . 240
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*2^4 - 2 = 14 usable addresses*
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#### CIDR /29
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*203.0.113.0/29*
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Network address
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11001011.00000000.01110001.00000*000*
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203 . 0 . 113 . 0
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Subnet Mask
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11111111.11111111.11111111.11111*000*
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255 . 255 . 255 . 248
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*2^4 - 2 = 6 usable addresses*
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#### CIDR /30
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**203.0.113.0/30**
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Network address
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11001011.00000000.01110001.000000*00*
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203 . 0 . 113 . 0
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Subnet Mask
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11111111.11111111.11111111.111111*00*
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255 . 255 . 255 . 252
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*2^4 - 2 = 6 usable addresses*
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This is the perfect CIDR for our 2 router
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The remaining addresses in the 20 203.0.113.0/24 address block (20 203.0.113.4 - 20 203.0.113.255)
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are now available to be used in other subnets!
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#### CIDR /31
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*203.0.113.0/31*
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2^1 -2= 0 usable addresses
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but for our point to point connection we can utilisize it
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no need for broadcast or network address
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In cisco device however you get a systeme warning
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```cisco
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Router(config-if)# ip address 203.0.113.0 255.255.255.254
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Warning use /31 mask on non point-to-pint interface cautiously
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```
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The remaining addresses in the 20 203.0.113.0/24 address block (20 203.0.113.2 - 203.0.113.255)
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are now available to be used in other network!
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#### CIDR /32
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*203.0.113.0/32*
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2^1 -2= -1 usable addresses
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can be used in static routes
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don't worry about them now
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## Review
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- [[CIDR]] (Classless Inter-Domain Routing)
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- The process of subnetting
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