2. By Joshua Newell

3. Protocols and Protocol Binding
Show Activity 6-1
Show adding protocols

4. TCP/IP Subnetting (continued..)

5. Review

6. Every IP Address has a node portion and a network portion
IP Addresses
Every IP Address has a node portion and a network portion
IP Address:
Network Portion:
Node Portion:

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:
Subnet Mask:
Network ID:

8. Subnet Mask and ANDing IP: 192.168.5.201 Subnet: 255.255.255.0
IP:
Subnet:
AND

9. TCP/IP Cheat Sheet: The Rules
The Subnet/network address is always hidden behind the 1s in the mask
IP:
Subnet:

10. 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
Subnet Mask > = =
These bits belong to the Big IP in the Sky
(we can’t change them)
These are the bits that we own
1s hide the subnet address
Breaks the rule! (except in CIDR)

11. TCP/IP Cheat Sheet: The Rules
(Except in special cases)
The all-1s and all-0s host addresses are invalid (Always)
Ex.
IP Address:
Subnet Mask: OR
IP Address:

12. Reason Behind the Rule
The all zeros host address is the same as the network ID
Ex. IP:
Subnet:
Network ID:
The all ones host address is reserved for the broadcast address

13. Classful Networking - <1993
Default Mask
Networks
Hosts A
127
16.8 mil B
16,384
65,534 C
2,097,152
254 D
Multicast E
Experimental/
Reserved
How do we get this?

14. Classful Networking - <1993
Leading Bits
Start
End A   B 10 C
110 D
1110 E
1111

15. Localhost Loopback Address
Reserved IP Ranges
Addresses
Purpose
Class
Total addresses
Zero Addresses A
16,777,216
   
Private IP addresses   
Localhost Loopback Address
Zeroconf / APIPA B
65,536  
1,048,576 C

16. NAT

17. CIDR (Classless Inter-Domain Routing) - ~>1993
Specifically, rather than allocating address blocks on eight-bit (i.e., octet) boundaries forcing 8, 16, or 24-bit prefixes, it used the technique of variable-length subnet masking (VLSM) to allow allocation on arbitrary-length prefixes.

18. My company needs 4 IPs
With classful subnetting, I would need a Class C (default subnet mask ) with 254 IPs What a waste!
How would we use CIDR?
We’re only going to need to look at the last octet
Remember that the subnet mask can’t have embedded 1s
So, we need to know what mask to use in the 4th octet

19. Let’s Look at the Cheat Sheet
Bits
Mask
Blocks
Nets
Hosts
256 1
254
128 2
126
192 64 2* 62
224 32 6 30
240 16 14
248 8
252 4 X
255
So we could use a network with a subnet mask of

20. CIDR Notation CIDR Notation Bits Mask Blocks Nets Hosts /24 0000 0000
# of 1s in the mask
CIDR Notation
CIDR Notation
Bits
Mask
Blocks
Nets
Hosts
/24
256 1
254
/25
128 2
126
/26
192 64 2* 62
/27
224 32 6 30
/28
240 16 14
/29
248 8
/30
252 4
/31 X
/32
255
A network with a subnet mask is called a /29

21. Using Subnetting to Segment a Network
Suppose we lease /24
(1 network, 254 hosts using 8 host bits)
We need to borrow some of our host bits and use them for network bits. IP
Mask

22. Ex. Use the /27 Mask
IP ( )
Mask ( )
What’s the block size? 32
Last Address
Computer Number
Block Size/ People Number
Last Address minus Block Size
0…31 | 32…63 | 64…95 | 96…127 | 128…159 | 160…191 | 192…223 | 224…255
Network ID for the 0 subnet
Network ID for the 1 subnet
Network ID for the 7 subnet

23. Why is it called the 0 subnet?
Ex. The /27 mask borrows 3 host bits and makes them network bits
.0 =
.224 =
Looking at the 3 borrowed bits:
Borrowed Bits Value
All Bits Value 1 32 2 64 3 96 4
128 5
160 6
192 7
224

24. Subnetting Exercise:
You’ve been hired to troubleshoot a problem network. The customer says that they are having problems with computers being able to connect to each other.
The network has computers with the following IPs:
All the computers are using the mask
Which computers are able to communicate?

25. Sample Problem:
Select the correct base network ID for /29
We could enumerate the /29 segments but that would take a while.
Instead, convert the IP to binary, but only the relevant octets.
27d -> binary =
Look at the cheatsheet to get the subnet mask for /29
>
AND the IP and the mask
AND
b-> 24d
So, the base network ID is

26. Exercise Select the correct base network ID for 203.121.45.31 /30IP
Mask
AND = 28

27. Subnetting Exercise 2:
Write out the subnets for the network, subnetted with the mask.
What’s the network address of the 0 subnet?
What’s the first host address in the 0 subnet?
What’s the last host address in the 2 subnet?
What’s the broadcast address for the 3 subnet?

28. TCP/IP Network Model

29. ARP Thanks! I’ll remember that for next time.
Hey everybody! Who is ?
Not me…
Not me…
Not me…
Hey ! I am. My MAC is 00:11:22:33:44:AB:CD:EF

30. Ports and Sockets I want to see what’s new on www.yahoo.com
Hey operating system, send an http get request to on Port 80
Ports and Sockets
I provide http services on port 80
I provide ftp services on port 20

31. I also need to get www.yahoo.com’s IP address…. OK, got it from DNS
Ok! But first I need to create a port for you so I can keep track of everything.
I also need to get IP address…. OK, got it from DNS
Dear {tcp, , 80},
Please send me your webpage. My address is: :49152
I got a message from It’s addressed on port That’s for Internet Explorer. Hey IE, here’s your page.
Thanks!
TCP: OPEN
Dear {tcp, , 49152},
I got your message. The webpage is as follows:….

32. DHCP Lease Process DHCP Discover (Broadcast) DHCP Offer (Broadcast)
DHCP Request (Broadcast)
DHCP Acknowledgment (Broadcast)

33. DHCP Relay Agent Routers do not forward broadcast traffic
(Does everyone in the world need to hear your LAN ARP requests?)

34. DHCP Relay Process DHCP Discover (Broadcast) DHCP Offer (Broadcast)
DHCP Request (Broadcast)
DHCP Acknowledgment (Broadcast)
DHCP Discover, DHCP Offer, DHCP Request,
DHCP Acknowledgment
(All done in Unicast)

35. DNS FQDN – Fully qualified domain name .(dot) = Root www.google.com.
com = Top Level Domain (TLD)
Google = Second-level domain
www = Alias or Host Name

36. DNS