1. Chapter 6 Addressing The Network – IPv4
Modified by Profs. Chen and Cappellino

2. Objectives In this chapter, you will learn to:
Explain the structure IP addressing and demonstrate the ability to convert between 8-bit binary and decimal numbers.
Given an IPv4 address, classify by type and describe how it is used in the network.
Explain how addresses are assigned to networks by ISPs and within networks by administrators.
Determine the network portion of the host address and explain the role of the subnet mask in dividing networks.
Given IPv4 addressing information and design criteria, calculate the appropriate addressing components.
Use common testing utilities to verify and test network connectivity and operational status of the IP protocol stack on a host.

3. The Anatomy of an IPv4 Address
At the Network layer, the packets need to be identified with the _________________________ of the two end systems.
Each device on a network must be ________________________
Each address is ________________________________
___________ use the addresses in _______________ format
__________ represent IPv4 addresses using _________________
Easier to remember and work with
Addresses expressed as dotted decimals separate each decimal number with a dot
Dotted decimal address: ______________________________
Each byte of the binary pattern, called an ______________.
An octet = _________________ = one decimal number of the address
Binary address (32- bit address):

4. The Anatomy of an IPv4 Address cont.
Network Portions
For each IPv4 address, some portion of the high-order bits represents the network address.
A _____________________________________ _________________________________________________________________________________________
Host Portions
The number of bits used in this host portion ________ ________________________________________________________________________________________
For example, to assign a unique address to 200 hosts, we would use the entire last octet. With 8 bits, a total of 256 different bit patterns can be achieved. This would mean that the bits for the upper three octets would represent the network portion.
Note: Calculating the number of hosts and determining which portion of the 32 bits refers to the network will be covered later in this chapter.

5. Please see the board for…
Binary to Decimal and Decimal to Binary conversions…

6. Types of Addresses in an IPv4 Network
Within the IPv4 network, there are _____ types of addresses:
________________ - The address by which we refer to the network
______________________ - A special address used to send data to all hosts in the network
______________________ - The unique addresses assigned to the end devices in the network
Network Address  /24
Example: shown below is "the network."
All hosts in the / 24 network will have the same network bits.
The lowest address is reserved for the network address.
This address has a 0 for each host bit in the host portion of the address.

7. Types of Addresses in an IPv4 Network cont..
Broadcast Address
A special address that ______ __________________________________________________
The broadcast address uses the highest address in the network range.
This is the address in which the bits in the ________________________
Example: For the network /24 the broadcast address would be
Host Addresses
______________ between the network address and the broadcast address _________ ________________________

8. Network Prefixes
How do we know how many bits represent the network portion and how many bits represent the host portion?
A prefix length.
The ____________________________ ______________________________________
For example, in /24, the /24 is the prefix length. This leaves the remaining 8 bits, the last octet, as the host portion.
Prefix values vary and ____________________ ____________________ _________________ ________________________ for each network.

9. Example…

10. Calculating Network, Hosts, and Broadcast Address
For example: /25.  (32 – 25 = 7 bits)
Network Address:
With a 25 bit prefix, the last 7 bits are host bits.
To represent the network address, all of these host bits are '0'.
This makes the network address /25.
First Host Address:
This is always ______________________________.
In this case, the ______________________________
This makes the lowest host address is
Broadcast Address
__________________________________________
This makes the broadcast address is
Last Host Address:
The _______________________________________ ________________________________________
It means the lowest host bit is a '0' and all other host bits as '1s'.
This makes the highest host address
Note: when working these problems- you need only expand from the divided octet to the end of the address (no need to expand all)

11. IPv4 Communication via Unicast, Broadcast, or Multicast
_________ - _______________________ __________________________________
__________ address is the address of the __________ host and the _______________ address is the address of the _____________________ device
Can be routed through an internetwork
Considered normal host-to-host communication
Throughout the course, communications are assumed Unicast unless otherwise noted

12. IPv4 Communication via Unicast, Broadcast, or Multicast
______________________-__________________________ ___________________________________________
Source address used is that of the originating host
Uses a special broadcast address destined for the destination devices
All hosts that receive a broadcast packet, process the packet as if it were a _______________________________
Broadcast transmission is used for purposes such as
Mapping upper layer addresses to lower layer addresses (_______)
Requesting an address (________________)
______________________________ by routing protocols
When a host needs information, the host sends a request, called a query, to the broadcast address.
All hosts in the network receive and process this query.
One or more of the hosts with the requested information will ________, typically using ____________________.

13. Broadcast Traffic cont…
Broadcast packets usually ________________ _______________ (aka limited broadcast).
There are __________________________:
________________ sent to all hosts on a _______________.
Useful for sending a broadcast to all hosts on a non-local network.
Routers do not forward directed broadcasts by default, they may be configured to do so.
For example, for a host outside of the network to communicate with the hosts within the /24 network, the destination address of the packet would be
____________________ used for communication to hosts _______________________________
Routers do not forward this broadcast to other directly connected networks
Routers form the boundary for a broadcast domain.
These packets use a destination IP address
Broadcast traffic should be limited so it does not adversely affect network or device performance

14. IPv4 Communication via Unicast, Broadcast, or Multicast
______________ transmission is designed to conserve bandwidth of the network.
It is the ______________________________________________ ______________________________
The source host can send a single packet that can reach thousands of destination hosts both locally and through an internetwork
Can someone give an example of multicast transmission?
Multicast clients and multicast group
__________________________________________________ are called _______________________________________.
The multicast clients use services initiated by a client program to subscribe to the multicast ____________ a group that _________________________________.
Each multicast group is represented by a single multicast destination address.
Hosts within a multicast group process packets addressed to a multicast address as well as packets addressed to its uniquely allocated unicast address.
IPv4 has set aside a special block of addresses from to for multicast groups addressing.

15. Reserved IPv4 Address Ranges
The IPv4 address range is to
Unicast ________________ Addresses
Host address range of _____________________________
within this range are many addresses that are already reserved for special purposes as we will see next section…
_________________ Addresses
Experimental address range __________________________
Reserved for research or experimentation but may be converted to usable addresses in the future
Multicast Addresses
SEE NEXT SLIDE…

16. Reserved IPv4 Address Ranges cont...
Multicast Addresses
_________________________________________
Multicast addresses subdivided into:
________________________________ The multicast addresses to
Addresses used for multicast groups on a local network
Routers use this type of multicast transmission to exchange routing information
___________________________________: The globally scoped addresses are to
Used to ____________________________________
__________________ addresses AKA Administratively scoped: The multicast addresses to
_____________________________________________

17. Public and Private Addresses
Used by networks that are _____________________________
Addresses must be __________________ to the Internet
______________________ addresses
Addresses that are _____________________________________ ________________________________________
Private address blocks :
to (_______________________)
to (___________________________)
to (_____________________________)
Hosts in _________________ may use the ________________ private addresses.
The hosts within the private networks use IP addresses that are _________________________________________
The ____________ or firewall device at the perimeter of these private networks __________________________ these addresses.

18. Network Address Translation (___)
______________________________________________________ for communicating to outside networks and across the Internet
translates private addresses to public addresses
The NAT can be implemented- by a device such as a router- at the edge of the private network.
NAT will be covered in detail in a subsequent course.

19. Special IPv4 Addresses
Certain addresses cannot be assigned to hosts or can be assigned but with restrictions.
Review: Describe the _______ and _________ Addresses
Can not be assigned to hosts
_____________________________
The default route is _____________________________-
The default route is __________________________________.
Reserves all addresses in the range so those addresses can not be assigned to hosts
_____________________________-
A reserved address which hosts use to ____________________
The loopback address __________________________.
You can ping the loopback address to ____________________ _____________________________________
Also used to test if the NIC on that device is functioning
Addresses in to are all reserved

20. Special IPv4 Addresses cont…
Reserved addresses that can be ____________________ _______________________________ if needed
Address block to (_____________) are reserved as link-local addresses.
Address block used when a host __________ automatically obtain an address from a ____________________
If this address appears in our configuration- tell us there’s a good chance something is wrong with the DHCP server
Hosts using link-local addresses can only _____________ ________________________________
__________________________Addresses
Reserved for __________________________________
In documentation, network examples etc.
Address block to (______________)
Network devices will accept these addresses in their configurations but will not appear on the Internet

21. Legacy IPv4 Addressing- Classes
Address ranges used to be grouped into specific sizes: class A, class B, class C, class D (multicast), and class E (experimental) addresses.
Known as _______________________________
Defined _________________________ as well as _____________________________________

22. Classes – cont… Class A Blocks Class B Blocks
Used for extremely large networks with more than 16 million host addresses.
____________________________________
first octet indicating the network portion of the address
remaining three octets used for host portion
128 possible class A networks, /8 to /8 excluding reserved addresses- 0. network, 10. network and the 127. network -- why?
Few companies could have or would need an entire class A address
Class B Blocks
Support the moderate to large size networks with more than 65,000 host addresses
_____________________________________
first two octets indicating the network portion of the address
remaining two octets used for host portion
Approximately 16,000 public class B networks, /16 to /16- excluding which addresses??

23. Legacy IPv4 Addressing Class C Blocks
Used for small networks with a maximum of 254 hosts.
__________________________________
first three octets indicating the network portion of the address
last octet used for host portion
Approximately 2 million class C networks, /16 to /16 excluding reserved addresses- Which ones??
Limitations to the Class-based System
_____________________________________________ which exhausted the availability of IPv4 addresses.
Classful system began phasing out in the late 1990s
______________________ Addressing
The system we __________________________________
_________________________________________ are assigned to companies or organizations without regard to the unicast class.

24. Planning to Address the Network
The allocation of addresses inside the network needs to be planned and documented for the purpose of:
________________________________________
Each host in an internetwork must have a unique address.
______________________________________
Especially important for hosts providing resources both internally and externally
__________________________________________
If we have proper planning and documentation of the network addressing, we can analyze traffic patterns and identify problems
Within a network, there are different types of hosts. What are some examples?

25. Planning to Address the Network
An important part of planning an IPv4 addressing scheme is deciding _______________ ________________________
If there are more devices than available public addresses, only those devices that will directly access the Internet - such as web servers - require a public address.
________________________ could be used for the rest
Another consideration- will devices need to be accessed from outside the local network?

26. Static or Dynamic Addressing for End User Devices
With a _______________________ _______________________________________________ for a host (figure).
Necessary to ___________________ of statically assigned IP address
Static address advantages:
Used when addresses should not change
________________________________ ________________ that need to be accessible to clients on the network.
Additionally, static assignment of addressing information ____________ ______________________________
Disadvantage: it can be_________________ to enter the information on each host.

27. Static or Dynamic Addressing for End User Devices
____________________________ ______________________________________________________ and other configuration information to hosts because it ____________________ _________________________
The configuration of the DHCP server requires the definition of a block of address, called an ____________________
Pool should exclude any addresses used by devices in manual assignment
Benefit of DHCP is that an address is _____________________________________________________________
When no longer needed by a host, addresses can be returned to the pool for reuse.

28. Assigning Addresses to Devices other than hosts
Recall: addresses for servers and peripherals should be _________________.
Predictable addresses for these devices are necessary
Hosts (usually servers) that are accessible from Internet must have a ___________ __________________________
If using private addressing within the network, the router or firewall at the perimeter of the network must be configured to translate the internal address of the server into a public address

29. Assigning Addresses to other Devices (cont.)
Intermediary devices are a concentration point for network traffic.
Almost all traffic within a network or between two networks passes through an intermediary device
Either for device management or for their operation- these intermediary devices should be __________________________ layer 3 address
Best practices is to assign these devices a network block in a different range than user device addresses
______________________________________________________________________________________
Each interface is in a different network and serves as the gateway for the hosts in that network.
The router interface uses _____________________________ in the network and this should be __________________ throughout all networks in the company
Many packets flow through a router’s interfaces so routers play a key role in _____________________________________

30. Good example graphic…

31. Who Assigns the Different Address?
A company that wishes to have network hosts accessible from the Internet must have a block of public addresses assigned.
Internet Assigned Numbers Authority (______________) ( is the master holder of the IP addresses.
In the mid-1990’s remaining IPv4 addresses were allocated to five other registries to manage for regional areas.
The 5 Regional Internet Registries (RIRs) are:

32. See three tier graphic on next slide
ISPs
To get access to the Internet, we have to connect our network to the Internet using an Internet Service Provider (ISP).
_____________________________________________ ___________________, etc.
Most companies obtain their IPv4 address blocks on loan from an ISP.
If an ISP is changed, the new ISP will provide new addresses from their address blocks.
ISPs are designated by a ______________ based on their proximity to the Internet backbone.
Lower tiers connect to the backbone via the next higher tier up
See three tier graphic on next slide

33. Which ISP tier are we looking for…
Which tier would be most reliable?
Which tier offers primarily only Internet connectivity and support?
Which tier is most expensive?
Which tier offers the most services to it’s customers?

34. Overview of IPv6
IPv6 came about as a result of the depletion of IPv4 addresses and offers the following features:
________________________________ - to expand addressing capabilities
Header format simplification - to _____________________________
Improved support for extensions and options - for increased __________/longevity and ____________________________________
Flow labeling capability - as QoS mechanisms
Authentication and privacy capabilities - to ________________________
IPv6 is a complete Layer 3 protocol suite including new routing protocols etc.
Transition to IPv6 is slow as new ways of dealing with IPv4 challenges keep it a widely used protocol suite.

35. Subnet Mask – Defining the network and Host Portions
A subnet mask is ____________________
Recall: IPv4 address has a network portion and a host portion.
To _____________________________, the devices use a separate 32-bit pattern called a subnet mask.
We express the subnet mask in the same dotted decimal format as the IPv4 address.
A __________________ in a bit position represents the ___________________
______________________ in a bit position represents the ___________________
As shown, a /24 prefix is expressed as a subnet mask: ( )
The zeroes represent the host portion of the address
NOTE: the ________________________ _____________________________________________________________________

36. ANDing – What is in our network?
Use the logical operator AND to _________ ____________ when ANDing is _________ _________________________________
Host address is ANDed with its subnet mask to determine the network address to which the host is associated.
The AND Operation
[true AND true = true]
[true AND false = false]
[false AND true = false]
[false AND false = false]
Host bits of a subnet mask are represented by 0’s so the host portion of the address will always be 0’s thereby giving us our network address
All the bits of the subnet mask that indicate ___________________________
ANDing will result in bits that are identical to the original network portion of the address

37. When is ANDing used?
As a packet arrives at a router, the __________________ on the _______________________________________ _________________________________________
The resulting network address is compared to possible routes from the routing table to determine an acceptable route
An __________________________________________ __________________________ with it’s own subnet mask
The host can then decide if a packet should be sent to a host in the local network or be sent to the gateway.
If the host network and destination network addresses do not match, the packet is sent to the gateway.
ANDing used in network
May need to determine what network a host is on or if two hosts are on the same network.
May need to use ANDing to troubleshoot routing issues
No calculators of any kind are permitted during certification exams

38. Example: Given 172.16.4.35/27 What is the Network Address?
First convert the IP address and Subnet Mask into binary
IP address
Subnet mask – how do we get the subnet mask value?
Network address

39. Basic Subnetting
Subnetting allows for ____________________ ________________ from a single address block.
smaller divisions of networks
A.K.A. ______________________
Recall from Chpt. 5: subnets are created by using one or more host bits as subnet bits.
Subnetting works by _____________________ to _____________________________________ of the address to create additional network bits.
The more host bits used, the more subnets that can be defined.
fewer host addresses are available per subnet.

40. Advantages of Subnetworks
Subnet addresses provide ________ and are assigned locally by a network administrator.
Improve ________________ through better use of host addressing
Can __________________________ on a subnetted network
________________________ into smaller, more efficient and manageable subnets

41. Subnet Addresses
Includes ___________ portion plus a ________ field and a ________________ field.
Bits are borrowed from the host field and are designated as the subnet field.
Network
Subnet
Host
Original Host portion (field)

42. Subnet Example Network Network Network Host S S H H H H H H
Say Two Bits are Borrowed from the Host Field to form a third layer of hierarchy - A Subnet Field

43. # of Subnets Created = ______________
Network
Network
Network
Host S S H H H H H H
The number of Subnets Created is calculated using the following formula:
# of Subnets Created = ______________

44. Subnets created after borrowingH H H H H H
Borrow 2 Bits = 22= 4 Subnets S S S H H H H H
Borrow 3 Bits = 23= 8 Subnets S S S S H H H H
Borrow 4 Bits = 24= 16 Subnets

45. How Many Hosts Per Subnet?
Network
Network
Network
Host S S H H H H H H
How is the number of Hosts per subnet calculated?
# Hosts = 26 = 64 hosts/subnet? ?

46. How Many Usable Hosts/Subnet?
6 Host Bits Remain = 26 = 64 Hosts
If there are 6 Host Bits remaining you do NOT get 64 Hosts/Subnet. Why?
Each subnet has its own ______________ ______________________ - Both of these ______________________________________!
Thus only _____ Usable Hosts are available.
6 Host Bits Remain = 26-2 = ____
Usable Hosts

47. SUMMARY: Formulas to Remember!
# Usable Subnets = 2# Borrowed Bits
Remember to subtract 2 for the Subnetwork Address and Subnetwork Broadcast Address.
# Usable Hosts/Subnet =
2# Host Bits Remaining-2

48. Example- 205.16.12.0 Requirement is 3 subnets
What is the default subnet mask?
This could also be written /24
Borrow 2 bits for the subnet mask
NNNNNNNN.NNNNNNNN.NNNNNNNN.SShhhhhh

49. Example cont…
What is the subnet mask (including borrowed bits)?
Value of the 4th octet=
27+26 = = 192
Resulting from the subnet
The Default

50. Step by Step EXAMPLE #2 We will subnet the IP address:
NOTE: For the reminder of the example, we will focus only the forth octet

51. Step #1
Determine the default subnet mask
Default subnet mask:

52. Step #2
You will be given the number of subnets needed. Use this info to determine how many bits to borrow from the host field.
Requirement:
6 subnets

53. Step #3
Figure the actual number of subnets by borrowing bits from host field.
Let’s see how many subnets we will have by borrowing 3 bits from the host.

54. Step #3 continued… 199.14.17.0 8 subnets 30 hosts for each subnet
S S S
H H H H H
8 subnets
How did we get 8?
30 hosts for each subnet
How did we get 30?

55. Step #3 continued… Recall:
You cannot use the first and last address within each subnet- they are reserved!
One is the broadcast address and one is the network address.

56. Step #4 Determine the subnet mask.
Default subnet mask for given example
BIT VALUE OF 4TH OCTET
S S S
H H H H H
Where S represents the borrowed bits for subnetting.

57. Step #4 continued…
Add the place values of S together to get the last octet decimal value of the subnet mask.
= 224
The subnet mask is:
The subnet mask is used to reveal the subnet and host address fields in IP addresses.

58. Step 5
Determine the ranges of host addresses for each subnet.

59. Step 5 continued… Subnet # Subnet Bits Host Bits In Decimal 000
000 1
001 2
010 3
011 4
100 5
101 6
110 7
111
Cont. on next slide…

60. Step 5 continued- Focusing in on the decimal portion…
In Decimal
Network Address
Host Range
Broadcast Address
/27
/27
/27
/27
/27
/27
/27
/27
25 -2 = 30 hosts

61. Subnetting and VLSM
Network administrators need to devise an internetwork addressing scheme to accommodate the maximum number of hosts for each network.
Point-to-point WAN links, only require a _____________________
Large building or department LAN, may need to accommodate _________________________________
Must also take into account projected future growth
_______________________________________ is an efficient addressing scheme for network admins. to use when breaking down a large network
Also referred to as using Variable Length Subnet Mask (________)
VLSM was designed to ___________________________
If all the subnets have the same requirements for the number hosts, these fixed size address blocks would be efficient. (see example to come…)

62. When using VLSM (or subnetting a subnet)…
First consider the ________________________ _______________________________ including devices, servers, router interfaces etc
Next, consider the _______________________ ____________________________ required based on common groupings of hosts.
Next, we need to start allocating addresses
We start with the ___________________________ __________________________________________

63. Pre- VLSM example Using “traditional” subnetting
waste of 28 host addresses from each subnet to simply address three point-to-point WAN networks
NO ROOM FOR NETWORK GROWTH!
See next slide for a better way …

64. Same scenario now using VLSM
Break the address into subnets of varying sizes
Use one of the three subnets which had previously been used to assign to a WAN link, and subnet it again with a 30-bit mask
See the next slide and the board for details…

65. VLSM example #1

66. VLSM example #1 cont… Questions: Why was /27 chosen to begin with?
Could we have selected ANY subnet to divide down further or did we NEED to choose subnet #6?
Why was /27 chosen to begin with?
Why was /30 subsequently chosen?

67. Graphic for Example #2 to follow…
500
200

68. Subnetting and VLSM – Example #2
In our example, the total number of hosts required by the entire corporate network including devices, servers, router interfaces etc is 800 hosts
To accommodate 800 hosts, we use binary arithmetic to allocate a _____________________________________________________________________________________________
Next, we consider the number of networks and the size of each required based on common groupings of hosts.
In our example: The company has 4 locations (4 LANs).
Each WAN link is a network. We create subnets for the WAN that interconnect different geographic locations.
Now we will need to start allocating addresses __________ ____________________________________________________________________________________________
See graphic on next slide

69. Recall: Number of network bits
Where shall we start?
500
Recall: Number of network bits
200

70. See board to understand this example…

71. What is Ping?
Ping is a utility for _____________________ _________________________________
Ping uses a _____________ that is a part on the TCP/IP suite called Internet Control Message Protocol (______).
Ping uses an ________________________ datagram.
If the host receives the Echo request, it ___________ ________________________________ datagram.
Ping measures the time required for the reply and ______________________________________
Recall: Pinging the Local Loopback- _______ tests the internal configuration of IP on the local host.
A _________________________________________ _________________________________________
Response is _____________________________________, or gateways are _________________________________.

72. Ping Gateway – Testing Connectivity to the Local LAN
Use ping to test the _______________ _______________________________________________________ the IP address of the __________________
A ping to the gateway indicates that the host and the router's interface serving as that gateway are both operational on the local network.
If gateway address does not respond:
Try _____________________________ in the local network.
If the gateway does not respond but another host does, possible ________________ _______________________________________ serving as the gateway.
If ________________ to that interface, that may ________________________ or responding to ping requests.
If either the gateway or another host responds, then the local hosts can successfully communicate over the local network.

73. Ping Remote Host – Testing Connectivity to Remote LAN
You can also __________________________ ______________________________________
If this ping is successful, it means that we have verified our host's communication on the local network, all the way through to the network of the remote host.
Remember, ____________________________ _________________________________________________ into or out of the corporate network.
Lack of a ping response could be due to security restrictions and not because of non-operational elements of the networks.

74. Tracertout (tracert) – Testing the Path
Traceroute (tracert) is ______________________ __________________________________
___________________________________ that were successfully reached along the path.
Used for ______________________________
If the data fails at some hop along the way, we have the address of the last router where the problem occurred or security restrictions are
Round Trip Time (RTT)
__________________________________________ and for the response from the host to return.
An ________________ (*) is used to indicate a _____________________________
What do you think a high response time indicates?

75. Tracertout (tracert) – Testing the Path
Time to Live (TTL)
Used to ________________ _________________________
When the TTL reaches zero, a router will not forward the packet and the packet is dropped.
The ____________________ _______________________ will be sent to the originating host and contain the IP address of the router that responded.
Sample Traceroute.

76. ICMPv4 – The Protocol Supporting Testing and Messaging
Although IPv4 is not a reliable protocol, it does _______________________________________ about issues related to the processing of IP packets under certain conditions- to be sent, using ICMPv4
__________________________________ and are often not allowed for security reasons.
ICMP messages that may be sent include the following five: 1.
Determines if a host is operational
basis of the ping utility.

77. ICMPv4 messages cont… 2.
Used to notify the sending host that the destination or service is unreachable
Destination Unreachable codes indicating why the packet could not be delivered are:
0 = net unreachable
1 = host unreachable
2 = protocol unreachable
3 = port unreachable 3.
Used by the router to indicate that a packet cannot be forwarded because the TTL field has expired.
ICMP Time Exceeded message also sent to the source host to inform the host of the reason the packet was dropped.

78. ICMPv4 messages cont… 4.
A router may use the ICMP Redirect Message to notify the hosts on a network that a _____________________ for a particular destination. 5.
Can be used to tell the source to temporarily _______ ______________________________ due to a lack of buffer space in which to receive incoming packets
Also notifies the source host for every message that it discards due to the lack of buffer space
A destination host may send a source quench message if datagrams arrive too fast to be processed.
The Transport layer at the source host end can use the TCP flow control mechanisms to adjust the transmission.