TCP/IP Subnetting

1
(No Transcript)
2
Welcome to Back!
3
TCP/IP Subnetting
4
Pop Quiz

• TCP/IP Cheat Sheet

5
IP Addresses

• My localhost -gt 192.168.5.201
• www.yahoo.com -gt 87.248.113.14

6
IP Addresses

• Every IP Address has a node portion and a
  network portion

• IP Address 192.168.5.201
• Network Portion 192.168.5.201
• Node Portion 192.168.5.201

7
Subnet Mask

• The subnet mask tells us which part of an IP
  address is the node portion vs. the network
  portion
• An IP address without a subnet mask is meaningless

• IP Address 192.168.5.201
• Subnet Mask 255.255.255.0
• --------------------------------------------------
  --
• Network ID 192.168.5.0

8
Binary ANDing

• AND is a mathematical operator just like
• (plus) and (minus)
• 1 1 2
• 1 AND 1 1

9
AND Truth Table

A B A AND
B --------------------------------------- FALSE
FALSE FALSE FALSE TRUE FALSE
TRUE FALSE FALSE TRUE TRUE TRUE
10
AND Truth Table

A B A AND B ----------------------
------- 0 0 0 0 1 0 1 0 0 1 1 1
11
AND Truth Table

0 AND 0 0 0 AND 1 0 1 AND 0 0 1 AND 1 1
12
Man vs Machine

• Human readable dotted decimal notation
• 192.168.5.201
• Each number represents an Octet or 8 bits
• What the computer sees

11000000.10101000.00000101.11001001
11000000101010000000010111001001
13
Subnet Mask and ANDing

• IP 192.168.5.201
• Subnet 255.255.255.0

IP 11000000.10101000.00000101.11001001 Subnet 1
1111111.11111111.11111111.00000000 ---------------
-------------------------------- 11000000.101010
00.00000101.00000000
IP 11000000.10101000.00000101.11001001 Subnet 1
1111111.11111111.11111111.00000000 ---------------
-------------------------------- 11000000.101010
00.00000101.00000000
AND
14
TCP/IP Cheat Sheet The Rules

• The Subnet/network address is always hidden
  behind the 1s in the mask

IP 11000000.10101000.00000101.11001001 Subnet 1
1111111.11111111.11111111.00000000 ---------------
-------------------------------- 11000000.101010
00.00000101.00000000
15
TCP/IP Cheat Sheet The Rules

• The Host/Node address is always hidden behind the
  0s in the mask

IP 11000000.10101000.00000101.11001001 Subnet 1
1111111.11111111.11111111.00000000 ---------------
-------------------------------- 11000000.101010
00.00000101.00000000
16
TCP/IP Cheat Sheet The Rules

• (Except in special cases)
• The all-1s and all-0s subnet addresses are
  invalid (but NOT in CIDR)

Ex.
0s hide the host address
Network ID 192.168.1.0 Subnet Mask
255.255.255.128 -gt 11111111.11111111.11111111.1000
0000
192.168.1.250 .11111010
-------------- 10000000
192.168.1.5 .00000101
-------------- 00000000
These bits belong to the Big IP in the Sky (we
cant change them)
These are the bits that we own
1s hide the subnet address
Breaks the rule! (except in CIDR)
17
TCP/IP Cheat Sheet The Rules

• (Except in special cases)
• The all-1s and all-0s host addresses are invalid
  (Always)

Ex.
IP Address 192.168.1.0 Subnet
Mask 255.255.255.0 OR IP Address
192.168.1.255 Subnet Mask 255.255.255.0
18
Reason Behind the Rule

• The all zeros host address is the same as the
  network ID
• Ex. IP 192.168.1.0
• Subnet 255.255.255.0
• ----------------------------------------
• Network ID 192.168.1.0
• The all ones host address is reserved for the
  broadcast address

19
(No Transcript)
20
Practice Problems

• 1 AND 1
• 1 AND 0
• 0 AND 1
• 0 AND 0
• 1111 AND 1010
• 0000 AND 1010
• 110101 AND 1101110

21
Practice Problems

• 110010b to Decimal
• 137d to Binary