CH4 SV_Subnetting

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CH4 SV_Subnetting

By S V
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  1. Why subdivide networks?

    Slide 1 - Why subdivide networks?

    • One IP Address won’t cover all the needs of a company
    • So – Divide into smaller networks to make more efficient use of the available IP addresses
    • You can separate the Payroll Department transmissions from the Accounting Department
    • You can separate out your Wi-Fi traffic into separate subnets
    • You can separate out those networks that have the most traffic into separate networks
  2. There are 2 methods to subnet

    Slide 2 - There are 2 methods to subnet

    • Using Classful addressing with “ANDing”
    • We’ll cover that first
    • Using Classless addressing (called CIDR)
    • CIDR is not apple cider
    • It stands for Classless Interdomain Routing
  3. You apply a “subnet mask” to a classful address

    Slide 3 - You apply a “subnet mask” to a classful address

    • Subnet mask is a series of 1s and 0s
    • Computer uses subnet mask to determine which part of the IP address is the network ID versus which part is the host
    • Subnet mask is all 1s (network) followed by all 0s (host)
    • For subnet mask 255.255.255.0,binary equivalent (Class C)11111111111111111111111100000000
    • Subnet Method 1 - Classful
  4. Classful IP Addressing (The Old Way)

    Slide 4 - Classful IP Addressing (The Old Way)

    • Classes A, B, C, D, and E or IPv4 Addresses
    • A, B, and C used by general population
    • Classful IP addressing – you’re stuck with just 3 subnet masks (one for Class A, one for Class B, and one for Class C)
    • For Class A: 255.0.0.0
    • For Class B: 255.255.0.0
    • For Class C: 255.255.255.0
    • rogerrhce.blogspot.com
    • Subnet Method 1 – Using Classful Addressing
  5. More info on “Classful” Addresses

    Slide 5 - More info on “Classful” Addresses

    • The 3 main classes used
    • Subnet Method 1 – Using Classful Addressing
    • But you’re stuck with just the numbers in these columns for your configurations
  6. So how do you start?

    Slide 6 - So how do you start?

    • Subnet mask has “1’s” to indicate how much of the IP address should be allocated for the network ID
    • 0’s in the subnet mask indicate the number of hosts
    • Each subnet begins with a network ID
    • To get the network ID, we do a process called “AND”ing…..it’s really simple.
    • To AND, you just lay the customer’s IP address and subnet mask on separate lines
    • Example of a Class C address and it’s default (only) subnetin classful addressing: 192.130.227.27 (put the IP address on top) 255.255.255.0 (the Subnet mask right below)
    • Subnet Method 1 – Using Classful Addressing
  7. How Do I “AND” to get the network address for the subnet?

    Slide 7 - How Do I “AND” to get the network address for the subnet?

    • To find a network address you “AND” the IP address and the subnet mask
    • NOTE I said you “AND” ---- NOT Add
    • ANDing
    • Computer uses a logical AND truth table to compare the full IP address of the computer to the subnet mask
    • A 0 and another 0 is 0
    • A 0 and 1 is 0
    • 1 and a 0 is 0
    • Only a 1 and 1 is a 1
    • Subnet Method 1 – Using Classful Addressing
  8. Show Me the Whole ANDing Example

    Slide 8 - Show Me the Whole ANDing Example

    • Result of ANDing 192.130.227.27 with the subnet mask 255.255.255.0
    • IP Address
    • 192.130.227.27
    • 1
    • 1
    • 0
    • 0
    • 0
    • 0
    • 0
    • 0
    • 1
    • 0
    • 0
    • 0
    • 0
    • 0
    • 1
    • 0
    • 1
    • 1
    • 1
    • 0
    • 0
    • 0
    • 1
    • 1
    • 0
    • 0
    • 0
    • 1
    • 1
    • 0
    • 1
    • 1
    • Subnet Mask
    • 255.255.255.0
    • 1
    • 1
    • 1
    • 1
    • 1
    • 1
    • 1
    • 1
    • 1
    • 1
    • 1
    • 1
    • 1
    • 1
    • 1
    • 1
    • 1
    • 1
    • 1
    • 1
    • 1
    • 1
    • 1
    • 1
    • 0
    • 0
    • 0
    • 0
    • 0
    • 0
    • 0
    • 0
    • AND Result
    • 1
    • 1
    • 0
    • 0
    • 0
    • 0
    • 0
    • 0
    • 1
    • 0
    • 0
    • 0
    • 0
    • 0
    • 1
    • 0
    • 1
    • 1
    • 1
    • 0
    • 0
    • 0
    • 1
    • 1
    • 0
    • 0
    • 0
    • 0
    • 0
    • 0
    • 0
    • 0
    • Change to Decimal
    • 128
    • 64
    • 0
    • 0
    • 0
    • 0
    • 0
    • 0
    • 128
    • 0
    • 0
    • 0
    • 0
    • 0
    • 2
    • 0
    • 128
    • 64
    • 32
    • 0
    • 0
    • 0
    • 2
    • 1
    • 0
    • 0
    • 0
    • 0
    • 0
    • 0
    • 0
    • 0
    • Network ID
    • 192
    • 130
    • 227
    • 0
    • A 0 and a 1 is a 0
    • A 1 and a 1 is a 1
    • Subnet Method 1 – Using Classful Addressing
    • And, you end up with your network ID for your network
  9. So What Does this Give You?

    Slide 9 - So What Does this Give You?

    • IP Address
    • 192.130.227.27
    • Subnet Mask
    • 255.255.255.0
    • Subnet Method 1 – Using Classful Addressing
    • Basically, in this case, there is
    • this is a Class “C” address and 256 hosts are available when using the subnet mask. Remember, in “classful” addressing, one size fits all for the class. So you only can use this subnet mask for Class C:
    • The default subnet mask for Class C is 255.255.255.0
    • 11111111 11111111 11111111 00000000
    • All 8 bits of the last octet are available for hosts. That is 256 (but is really 254 if you listened to Professor Messer
  10. Method 2 - Classless IP Addressing (Newer Way)

    Slide 10 - Method 2 - Classless IP Addressing (Newer Way)

    • What if you were not limited to “classes” and only 3 subnet addresses?
    • In this method, class of an IP address is not considered
    • Instead, there is a Standard notation that indicates network ID and host ID of an IP address
    • Format of this notation is similar to 192.130.227.27/nn
    • /nn indicates how many of the total 32 bits of the IP address’ binary form are to be used for the network IP portion
    • i.e., tells what the subnet mask is
    • /nn can be any number between 1 and 32, but 2 through 30 are used in practice
    • This is referred to as “Classless Inter-domain Routing” (CIDR)
  11. One more time - how CIDR works

    Slide 11 - One more time - how CIDR works

    • In CIDR, the IP address is followed by a 2 digit number
    • The 2 digits specify how long the network portion of the address is
    • Example: CIDR notation is 192.130.227.27/12
    • Use the value 8 to determine how many 1’s in the subnet mask in each octet. Example: 12 – 8 = 4
    • In example above, first octet has eight 1s, second octet uses the remaining four 1’s
    • So an octet with eight 1’s is 255, so first octet of the subnet mask is 255
    • tweakyourslides.wordpress.com
    • Subnet Method 2 – CIDR
  12. Look at the Actual Subnet Mask  (using CIDR)

    Slide 12 - Look at the Actual Subnet Mask (using CIDR)

    • Again example: CIDR notation is 192.130.227.27/12
    • Again – first 12 numbers in the subnet mask (binary) are 1’s and the others are 0’s
    • Here is what that looks like:
    • 11111111 11110000 00000000 00000000
    • So Here is what the above binary number looks like in decimal:
    • 255.240.0.0
    • The next slide will show you where we got the 240
    • The 255 comes from the first octet having all 1’s
    • 255.240
    • Subnet Method 2 – CIDR
  13. Determine Subnet Mask Using CIDR

    Slide 13 - Determine Subnet Mask Using CIDR

    • How did we get the 240? First four places in the second octet of the subnet mask starting with the leftmost place are all 1’s
    • Binary = 11110000
    • 11110000 value converts to 240
    • 128 + 64 + 32 + 16 = 240
    • Subnet Method 2 – CIDR
  14. Determine Subnet Mask Using CIDR

    Slide 14 - Determine Subnet Mask Using CIDR

    • The value 240 should be in the second octet of the subnet mask
    • So you put 1’s in the first 12 positions of the subnet mask (because the CIDR notation was /12)
    • and there are no 1’s in the last two octets and so they will equal 0
    • The subnet mask that results from the CIDR notation 192.130.227.27/12 is therefore 255.240.0.0
    • Subnet Method 2 – CIDR
  15. More CIDR Examples and a Table

    Slide 15 - More CIDR Examples and a Table

    • 192.130.227.27/8 indicates the subnet mask is 255.0.0.0
    • 192.130.227.27/16 indicates the subnet mask is 255.255.0.0
    • 192.130.227.27/24 indicates the subnet mask is 255.255.255.0
    • Here is the rest of the table
    • www.certificationkits.com
    • Subnet Method 2 – CIDR
  16. So What is the Value of “CIDR”?

    Slide 16 - So What is the Value of “CIDR”?

    • It’s not tied to a Class A, B, C – not rigid
    • Allows flexibility in subnetting so you are not limited to just those classes.
    • CIDR notation can determine sub-network ranges
    • Subnet Method 2 – CIDR
  17. CIDR Values &Their Subnet Masks

    Slide 17 - CIDR Values &Their Subnet Masks

    • CIDR VALUE
    • Subnet Mask – note the Number of 1's in Subnet Mask
    • Looks like this in Decimal
    • Subnet Increment Value
    • Networks Available
    • Usable Networks
    • Hosts Available
    • Usable Hosts
    • /8
    • 11111111 00000000 00000000 00000000
    • 255.0.0.0
    • /9
    • 11111111 10000000 00000000 00000000
    • 255.128.0.0
    • /10
    • 11111111 11000000 00000000 00000000
    • 255.192.0.0
    • /11
    • 11111111 11100000 00000000 00000000
    • 255.224.0.0
    • /12
    • 11111111 11110000 00000000 00000000
    • 255.240.0.0
    • /13
    • 11111111 11111000 00000000 00000000
    • 255.248.0.0
    • /14
    • 11111111 11111100 00000000 00000000
    • 255.252.0.0
    • /15
    • 11111111 11111110 00000000 00000000
    • 255.254.0.0
    • /16
    • 11111111 11111111 00000000 00000000
    • 255.255.0.0
    • /17
    • 11111111 11111111 10000000 00000000
    • 255.255.128.0
    • /18
    • 11111111 11111111 11000000 00000000
    • 255.255.192.0
    • /19
    • 11111111 11111111 11100000 00000000
    • 255.255.224.0
    • /20
    • 11111111 11111111 11110000 00000000
    • 255.255.240.0
    • /21
    • 11111111 11111111 11111000 00000000
    • 255.255.248.0
    • /22
    • 11111111 11111111 11111100 00000000
    • 255.255.252.0
    • /23
    • 11111111 11111111 11111110 00000000
    • 255.255.254.0
    • /24
    • 11111111 11111111 11111111 00000000
    • 255.255.255.0
    • 0
    • 0
    • 0
    • /25
    • 11111111 11111111 11111111 10000000
    • 255.255.255.128
    • 128
    • 2
    • 0
    • /26
    • 11111111 11111111 11111111 11000000
    • 255.255.255.192
    • 64
    • 4
    • 2
    • 64
    • 62
    • /27
    • 11111111 11111111 11111111 11100000
    • 255.255.255.224
    • 32
    • 8
    • 6
    • 32
    • 30
    • /28
    • 11111111 11111111 11111111 11110000
    • 255.255.255.240
    • 16
    • 16
    • 14
    • 16
    • 14
    • /29
    • 11111111 11111111 11111111 11111000
    • 255.255.255.248
    • 8
    • 32
    • 30
    • 8
    • 6
    • /30
    • 11111111 11111111 11111111 11111100
    • 255.255.255.252
    • 4
    • 64
    • 62
    • 4
    • 2
    • /31
    • 11111111 11111111 11111111 11111110
    • 255.255.255.254
    • 2
    • 128
    • 0
    • 2
    • /32
    • 11111111 11111111 11111111 11111111
    • 255.255.255.255
    • 1
    • 256
    • 0
    • Subnet Method 2 – CIDR
  18. Now we can use this chart to determine Subnets (last 9 rows of previous slide)

    Slide 18 - Now we can use this chart to determine Subnets (last 9 rows of previous slide)

    • /32
    • /31
    • /30
    • /29
    • /28
    • /27
    • /26
    • /24
    • /25
    • See the last 9 rows of the previous slide
    • CIDR Values
    • Subnet Method 2 – CIDR
  19. Value Changes by Increments of 64 in the Last Octet of 207.253.187.0/26

    Slide 19 - Value Changes by Increments of 64 in the Last Octet of 207.253.187.0/26

    • 11111111 11111111 11111111 11000000
    • Now, notice that in the last octet (on the right), that leaves 6 zeroes for hosts.
    • Add up all the positions for the hosts 32+16+8+4+2+1 = 63It is 64 since you allow for a starting number of 0 (0 to 63 = 64 digits)
    • Remember what the /26 means – it means 26 ONES.
    • Here is Where does the 64 come from?
    • 64
    • 64
    • 64
    • Subnet Method 2 – CIDR
  20. Absolute Network Ranges UsingCIDR 207.253.187.0/26 (continued)

    Slide 20 - Absolute Network Ranges UsingCIDR 207.253.187.0/26 (continued)

    • 0 – 63 is 64
    • Subnet Method 2 – CIDR
  21. Usable Network Ranges from  Usable Networks, Using CIDR For 207.153.187.0/26

    Slide 21 - Usable Network Ranges from Usable Networks, Using CIDR For 207.153.187.0/26

  22. Another example: 207.253.187.0/27

    Slide 22 - Another example: 207.253.187.0/27

    • 11111111 111111111 11111111 11100000
    • Remember – the 27 means 27 1’s in the subnet mask
    • 16+8+4+2+1 is 31 and you add 1 for the fact you start at 0, giving us 32 increment
    • 32
    • 32
    • Subnet Method 2 – CIDR
  23. Final Tidbit on IPv4 – Some IP addresses are “Reserved”

    Slide 23 - Final Tidbit on IPv4 – Some IP addresses are “Reserved”

    • Recognize your home computer addresses here
    • Lots of organization use sub addresses in this block range