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The document provides an overview of IPv4 addressing, detailing the structure of IPv4 addresses, the use of subnet masks, and the concept of prefix length. It discusses different types of IP addresses, including public, private, multicast, and broadcast addresses, alongside their routing implications. The text also covers network segmentation, including the benefits of subnetting and its impact on network performance and broadcast traffic management.

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Module 11: IPv4 Addressing Instructor Materials Introduction to Networks v7.0 (ITN)
2 © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 11.1 IPv4 Address Structure
3 © 2019, 2021 Cisco and/or its affiliates. All rights reserved. Cisco Confidential IPv4 Address Structure Network and Host Portions • An IPv4 address is a 32-bit hierarchical address that is made up of a network portion and a host portion. • When determining the network portion versus the host portion, you must look at the 32-bit stream. • A subnet mask is used to determine the network and host portions.
4 © 2019, 2021 Cisco and/or its affiliates. All rights reserved. Cisco Confidential IPv4 Address Structure The Subnet Mask • To identify the network and host portions of an IPv4 address, the subnet mask is compared to the IPv4 address bit for bit, from left to right. • The actual process used to identify the network and host portions is called ANDing.
5 © 2019, 2021 Cisco and/or its affiliates. All rights reserved. Cisco Confidential IPv4 Address Structure The Prefix Length • A prefix length is a less cumbersome method used to identify a subnet mask address. • The prefix length is the number of bits set to 1 in the subnet mask. • It is written in “slash notation” therefore, count the number of bits in the subnet mask and prepend it with a slash. Subnet Mask 32-bit Address Prefix Length 255.0.0.0 11111111.00000000.00000000.00000000 /8 255.255.0.0 11111111.11111111.00000000.00000000 /16 255.255.255.0 11111111.11111111.11111111.00000000 /24 255.255.255.128 11111111.11111111.11111111.10000000 /25 255.255.255.192 11111111.11111111.11111111.11000000 /26 255.255.255.224 11111111.11111111.11111111.11100000 /27 255.255.255.240 11111111.11111111.11111111.11110000 /28 255.255.255.248 11111111.11111111.11111111.11111000 /29 255.255.255.252 11111111.11111111.11111111.11111100 /30
6 © 2019, 2021 Cisco and/or its affiliates. All rights reserved. Cisco Confidential IPv4 Address Structure Determining the Network: Logical AND • A logical AND Boolean operation is used in determining the network address. • Logical AND is the comparison of two bits where only a 1 AND 1 produces a 1 and any other combination results in a 0. • 1 AND 1 = 1, 0 AND 1 = 0, 1 AND 0 = 0, 0 AND 0 = 0 • 1 = True and 0 = False • To identify the network address, the host IPv4 address is logically ANDed, bit by bit, with the subnet mask to identify the network address.
7 © 2019, 2021 Cisco and/or its affiliates. All rights reserved. Cisco Confidential IPv4 Address Structure Network, Host, and Broadcast Addresses • Within each network are three types of IP addresses: • Network address • Host addresses • Broadcast address Network Portion Host Portion Host Bits Subnet mask 255.255.255.0 or /24 255 255 255 11111111 11111111 11111111 0 00000000 Network address 192.168.10.0 or /24 192 168 10 11000000 10100000 00001010 0 00000000 All 0s First address 192.168.10.1 or /24 192 168 10 11000000 10100000 00001010 1 00000001 All 0s and a 1 Last address 192.168.10.254 or /24 192 168 10 11000000 10100000 00001010 254 11111110 All 1s and a 0 Broadcast address 192.168.10.255 or /24 192 168 10 11000000 10100000 00001010 255 11111111 All 1s
8 © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 11.2 IPv4 Unicast, Broadcast, and Multicast
9 © 2019, 2021 Cisco and/or its affiliates. All rights reserved. Cisco Confidential IPv4 Unicast, Broadcast, and Multicast Unicast • Unicast transmission is sending a packet to one destination IP address. • For example, the PC at 172.16.4.1 sends a unicast packet to the printer at 172.16.4.253.
10 © 2019, 2021 Cisco and/or its affiliates. All rights reserved. Cisco Confidential IPv4 Unicast, Broadcast, and Multicast Broadcast • Broadcast transmission is sending a packet to all other destination IP addresses. • For example, the PC at 172.16.4.1 sends a broadcast packet to all IPv4 hosts.
11 © 2019, 2021 Cisco and/or its affiliates. All rights reserved. Cisco Confidential IPv4 Unicast, Broadcast, and Multicast Multicast • Multicast transmission is sending a packet to a multicast address group. • For example, the PC at 172.16.4.1 sends a multicast packet to the multicast group address 224.10.10.5.
12 © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 11.3 Types of IPv4 Addresses
13 © 2019, 2021 Cisco and/or its affiliates. All rights reserved. Cisco Confidential Types of IPv4 Addresses Public and Private IPv4 Addresses • As defined in in RFC 1918, public IPv4 addresses are globally routed between internet service provider (ISP) routers. • However, private addresses are not globally routable. • Private addresses are common blocks of addresses used by most organizations to assign IPv4 addresses to internal hosts. • Private IPv4 addresses are not unique and can be used internally within any network. Network Address and Prefix RFC 1918 Private Address Range 10.0.0.0/8 10.0.0.0 - 10.255.255.255 172.16.0.0/12 172.16.0.0 - 172.31.255.255 192.168.0.0/16 192.168.0.0 - 192.168.255.255
14 © 2019, 2021 Cisco and/or its affiliates. All rights reserved. Cisco Confidential Types of IPv4 Addresses Routing to the Internet • Network Address Translation (NAT) translates private IPv4 addresses to public IPv4 addresses. • NAT is typically enabled on the edge router connecting to the internet. • It translates the internal private address to a public global IP address.
15 © 2019, 2021 Cisco and/or its affiliates. All rights reserved. Cisco Confidential Types of IPv4 Addresses Special Use IPv4 Addresses Loopback addresses • 127.0.0.0 /8 (127.0.0.1 to 127.255.255.254) • Commonly identified as only 127.0.0.1 • Used on a host to test if TCP/IP is operational. Link-Local addresses • 169.254.0.0 /16 (169.254.0.1 to 169.254.255.254) • Commonly known as the Automatic Private IP Addressing (APIPA) addresses or self- assigned addresses. • Used by Windows DHCP clients to self-configure when no DHCP servers are available.
16 © 2019, 2021 Cisco and/or its affiliates. All rights reserved. Cisco Confidential Types of IPv4 Addresses Legacy Classful Addressing RFC 790 (1981) allocated IPv4 addresses in classes • Class A (0.0.0.0/8 to 127.0.0.0/8) • Class B (128.0.0.0 /16 – 191.255.0.0 /16) • Class C (192.0.0.0 /24 – 223.255.255.0 /24) • Class D (224.0.0.0 to 239.0.0.0) • Class E (240.0.0.0 – 255.0.0.0) • Classful addressing wasted many IPv4 addresses. Classful address allocation was replaced with classless addressing which ignores the rules of classes (A, B, C).
17 © 2019, 2021 Cisco and/or its affiliates. All rights reserved. Cisco Confidential Types of IPv4 Addresses Assignment of IP Addresses • The Internet Assigned Numbers Authority (IANA) manages and allocates blocks of IPv4 and IPv6 addresses to five Regional Internet Registries (RIRs). • RIRs are responsible for allocating IP addresses to ISPs who provide IPv4 address blocks to smaller ISPs and organizations.
18 © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 11.4 Network Segmentation
19 © 2019, 2021 Cisco and/or its affiliates. All rights reserved. Cisco Confidential Network Segmentation Broadcast Domains and Segmentation • Many protocols use broadcasts or multicasts (e.g., ARP use broadcasts to locate other devices, hosts send DHCP discover broadcasts to locate a DHCP server.) • Switches propagate broadcasts out all interfaces except the interface on which it was received. • The only device that stops broadcasts is a router. • Routers do not propagate broadcasts. • Each router interface connects to a broadcast domain and broadcasts are only propagated within that specific broadcast domain.
20 © 2019, 2021 Cisco and/or its affiliates. All rights reserved. Cisco Confidential Network Segmentation Problems with Large Broadcast Domains • A problem with a large broadcast domain is that these hosts can generate excessive broadcasts and negatively affect the network. • The solution is to reduce the size of the network to create smaller broadcast domains in a process called subnetting. • Dividing the network address 172.16.0.0 /16 into two subnets of 200 users each: 172.16.0.0 /24 and 172.16.1.0 /24. • Broadcasts are only propagated within the smaller broadcast domains.
21 © 2019, 2021 Cisco and/or its affiliates. All rights reserved. Cisco Confidential Network Segmentation Reasons for Segmenting Networks • Subnetting reduces overall network traffic and improves network performance. • It can be used to implement security policies between subnets. • Subnetting reduces the number of devices affected by abnormal broadcast traffic. • Subnets are used for a variety of reasons including by: Location Group or Function Device Type
22 © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 11.5 Subnet an IPv4 Network
23 © 2019, 2021 Cisco and/or its affiliates. All rights reserved. Cisco Confidential Subnet an IPv4 Network Subnet on an Octet Boundary • Networks are most easily subnetted at the octet boundary of /8, /16, and /24. • Notice that using longer prefix lengths decreases the number of hosts per subnet. Prefix Length Subnet Mask Subnet Mask in Binary (n = network, h = host) # of hosts /8 255.0.0.0 nnnnnnnn.hhhhhhhh.hhhhhhhh.hhhhhhhh 11111111.00000000.00000000.00000000 16,777,214 /16 255.255.0.0 nnnnnnnn.nnnnnnnn.hhhhhhhh.hhhhhhhh 11111111.11111111.00000000.00000000 65,534 /24 255.255.255.0 nnnnnnnn.nnnnnnnn.nnnnnnnn.hhhhhhhh 11111111.11111111.11111111.00000000 254
24 © 2019, 2021 Cisco and/or its affiliates. All rights reserved. Cisco Confidential Subnet an IPv4 Network Subnet on an Octet Boundary (Cont.) • In the first table 10.0.0.0/8 is subnetted using /16 and in the second table, a /24 mask. Subnet Address (256 Possible Subnets) Host Range (65,534 possible hosts per subnet) Broadcast 10.0.0.0/16 10.0.0.1 - 10.0.255.254 10.0.255.255 10.1.0.0/16 10.1.0.1 - 10.1.255.254 10.1.255.255 10.2.0.0/16 10.2.0.1 - 10.2.255.254 10.2.255.255 10.3.0.0/16 10.3.0.1 - 10.3.255.254 10.3.255.255 10.4.0.0/16 10.4.0.1 - 10.4.255.254 10.4.255.255 10.5.0.0/16 10.5.0.1 - 10.5.255.254 10.5.255.255 10.6.0.0/16 10.6.0.1 - 10.6.255.254 10.6.255.255 10.7.0.0/16 10.7.0.1 - 10.7.255.254 10.7.255.255 ... ... ... 10.255.0.0/16 10.255.0.1 - 10.255.255.254 10.255.255.255 Subnet Address (65,536 Possible Subnets) Host Range (254 possible hosts per subnet) Broadcast 10.0.0.0/24 10.0.0.1 - 10.0.0.254 10.0.0.255 10.0.1.0/24 10.0.1.1 - 10.0.1.254 10.0.1.255 10.0.2.0/24 10.0.2.1 - 10.0.2.254 10.0.2.255 … … … 10.0.255.0/24 10.0.255.1 - 10.0.255.254 10.0.255.255 10.1.0.0/24 10.1.0.1 - 10.1.0.254 10.1.0.255 10.1.1.0/24 10.1.1.1 - 10.1.1.254 10.1.1.255 10.1.2.0/24 10.1.2.1 - 10.1.2.254 10.1.2.255 … … … 10.100.0.0/24 10.100.0.1 - 10.100.0.254 10.100.0.255 ... ... ... 10.255.255.0/24 10.255.255.1 - 10.2255.255.254 10.255.255.255
25 © 2019, 2021 Cisco and/or its affiliates. All rights reserved. Cisco Confidential Subnet an IPv4 Network Subnet within an Octet Boundary • Refer to the table to see six ways to subnet a /24 network. Prefix Length Subnet Mask Subnet Mask in Binary (n = network, h = host) # of subnets # of hosts /25 255.255.255.128 nnnnnnnn.nnnnnnnn.nnnnnnnn.nhhhhhhh 11111111.11111111.11111111.10000000 2 126 /26 255.255.255.192 nnnnnnnn.nnnnnnnn.nnnnnnnn.nnhhhhhh 11111111.11111111.11111111.11000000 4 62 /27 255.255.255.224 nnnnnnnn.nnnnnnnn.nnnnnnnn.nnnhhhhh 11111111.11111111.11111111.11100000 8 30 /28 255.255.255.240 nnnnnnnn.nnnnnnnn.nnnnnnnn.nnnnhhhh 11111111.11111111.11111111.11110000 16 14 /29 255.255.255.248 nnnnnnnn.nnnnnnnn.nnnnnnnn.nnnnnhhh 11111111.11111111.11111111.11111000 32 6 /30 255.255.255.252 nnnnnnnn.nnnnnnnn.nnnnnnnn.nnnnnnhh 11111111.11111111.11111111.11111100 64 2
26 © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 11.6 Subnet a Slash 16 and a Slash 8 Prefix
27 © 2019, 2021 Cisco and/or its affiliates. All rights reserved. Cisco Confidential Subnet a Slash 16 and a Slash 8 Prefix Create Subnets with a Slash 16 prefix • The table highlights all the possible scenarios for subnetting a /16 prefix. Prefix Length Subnet Mask Network Address (n = network, h = host) # of subnets # of hosts /17 255.255.128.0 nnnnnnnn.nnnnnnnn.nhhhhhhh.hhhhhhhh 11111111.11111111.10000000.00000000 2 32766 /18 255.255.192.0 nnnnnnnn.nnnnnnnn.nnhhhhhh.hhhhhhhh 11111111.11111111.11000000.00000000 4 16382 /19 255.255.224.0 nnnnnnnn.nnnnnnnn.nnnhhhhh.hhhhhhhh 11111111.11111111.11100000.00000000 8 8190 /20 255.255.240.0 nnnnnnnn.nnnnnnnn.nnnnhhhh.hhhhhhhh 11111111.11111111.11110000.00000000 16 4094 /21 255.255.248.0 nnnnnnnn.nnnnnnnn.nnnnnhhh.hhhhhhhh 11111111.11111111.11111000.00000000 32 2046 /22 255.255.252.0 nnnnnnnn.nnnnnnnn.nnnnnnhh.hhhhhhhh 11111111.11111111.11111100.00000000 64 1022 /23 255.255.254.0 nnnnnnnn.nnnnnnnn.nnnnnnnh.hhhhhhhh 11111111.11111111.11111110.00000000 128 510 /24 255.255.255.0 nnnnnnnn.nnnnnnnn.nnnnnnnn.hhhhhhhh 11111111.11111111.11111111.00000000 256 254 /25 255.255.255.128 nnnnnnnn.nnnnnnnn.nnnnnnnn.nhhhhhhh 11111111.11111111.11111111.10000000 512 126 /26 255.255.255.192 nnnnnnnn.nnnnnnnn.nnnnnnnn.nnhhhhhh 11111111.11111111.11111111.11000000 1024 62 /27 255.255.255.224 nnnnnnnn.nnnnnnnn.nnnnnnnn.nnnhhhhh 11111111.11111111.11111111.11100000 2048 30 /28 255.255.255.240 nnnnnnnn.nnnnnnnn.nnnnnnnn.nnnnhhhh 11111111.11111111.11111111.11110000 4096 14 /29 255.255.255.248 nnnnnnnn.nnnnnnnn.nnnnnnnn.nnnnnhhh 11111111.11111111.11111111.11111000 8192 6 /30 255.255.255.252 nnnnnnnn.nnnnnnnn.nnnnnnnn.nnnnnnhh 11111111.11111111.11111111.11111100 16384 2
28 © 2019, 2021 Cisco and/or its affiliates. All rights reserved. Cisco Confidential Subnet a Slash 16 and a Slash 8 Prefix Create 100 Subnets with a Slash 16 prefix Consider a large enterprise that requires at least 100 subnets and has chosen the private address 172.16.0.0/16 as its internal network address. • The figure displays the number of subnets that can be created when borrowing bits from the third octet and the fourth octet. • Notice there are now up to 14 host bits that can be borrowed (i.e., last two bits cannot be borrowed). To satisfy the requirement of 100 subnets for the enterprise, 7 bits (i.e., 27 = 128 subnets) would need to be borrowed (for a total of 128 subnets).
29 © 2019, 2021 Cisco and/or its affiliates. All rights reserved. Cisco Confidential Subnet a Slash 16 and a Slash 8 Prefix Create 1000 Subnets with a Slash 8 prefix Consider a small ISP that requires 1000 subnets for its clients using network address 10.0.0.0/8 which means there are 8 bits in the network portion and 24 host bits available to borrow toward subnetting. • The figure displays the number of subnets that can be created when borrowing bits from the second and third. • Notice there are now up to 22 host bits that can be borrowed (i.e., last two bits cannot be borrowed). To satisfy the requirement of 1000 subnets for the enterprise, 10 bits (i.e., 210=1024 subnets) would need to be borrowed (for a total of 128 subnets)
30 © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 11.7 Subnet to Meet Requirements
32 © 2019, 2021 Cisco and/or its affiliates. All rights reserved. Cisco Confidential Subnet to Meet Requirements Minimize Unused Host IPv4 Addresses and Maximize Subnets There are two considerations when planning subnets: • The number of host addresses required for each network • The number of individual subnets needed Prefix Length Subnet Mask Subnet Mask in Binary (n = network, h = host) # of subnets # of hosts /25 255.255.255.128 nnnnnnnn.nnnnnnnn.nnnnnnnn.nhhhhhhh 11111111.11111111.11111111.10000000 2 126 /26 255.255.255.192 nnnnnnnn.nnnnnnnn.nnnnnnnn.nnhhhhhh 11111111.11111111.11111111.11000000 4 62 /27 255.255.255.224 nnnnnnnn.nnnnnnnn.nnnnnnnn.nnnhhhhh 11111111.11111111.11111111.11100000 8 30 /28 255.255.255.240 nnnnnnnn.nnnnnnnn.nnnnnnnn.nnnnhhhh 11111111.11111111.11111111.11110000 16 14 /29 255.255.255.248 nnnnnnnn.nnnnnnnn.nnnnnnnn.nnnnnhhh 11111111.11111111.11111111.11111000 32 6 /30 255.255.255.252 nnnnnnnn.nnnnnnnn.nnnnnnnn.nnnnnnhh 11111111.11111111.11111111.11111100 64 2
33 © 2019, 2021 Cisco and/or its affiliates. All rights reserved. Cisco Confidential Subnet to Meet Requirements Example: Efficient IPv4 Subnetting • In this example, corporate headquarters has been allocated a public network address of 172.16.0.0/22 (10 host bits) by its ISP providing 1,022 host addresses. • There are five sites and therefore five internet connections which means the organization requires 10 subnets with the largest subnet requires 40 addresses. • It allocated 10 subnets with a /26 (i.e., 255.255.255.192) subnet mask.
34 © 2019, 2021 Cisco and/or its affiliates. All rights reserved. Cisco Confidential Subnet to Meet Requirements Packet Tracer – Subnetting Scenario In this Packet Tracer, you will do the following: • Design an IP Addressing Scheme • Assign IP Addresses to Network Devices and Verify Connectivity
35 © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 11.8 VLSM
36 © 2019, 2021 Cisco and/or its affiliates. All rights reserved. Cisco Confidential VLSM IPv4 Address Conservation Given the topology, 7 subnets are required (i.e, four LANs and three WAN links) and the largest number of host is in Building D with 28 hosts. • A /27 mask would provide 8 subnets of 30 host IP addresses and therefore support this topology.
37 © 2019, 2021 Cisco and/or its affiliates. All rights reserved. Cisco Confidential VLSM IPv4 Address Conservation (Cont.) However, the point-to-point WAN links only require two addresses and therefore waste 28 addresses each for a total of 84 unused addresses. • Applying a traditional subnetting scheme to this scenario is not very efficient and is wasteful. • VLSM was developed to avoid wasting addresses by enabling us to subnet a subnet.
38 © 2019, 2021 Cisco and/or its affiliates. All rights reserved. Cisco Confidential VLSM VLSM • The left side displays the traditional subnetting scheme (i.e., the same subnet mask) while the right side illustrates how VLSM can be used to subnet a subnet and divided the last subnet into eight /30 subnets. • When using VLSM, always begin by satisfying the host requirements of the largest subnet and continue subnetting until the host requirements of the smallest subnet are satisfied. • The resulting topology with VLSM applied.
39 © 2019, 2021 Cisco and/or its affiliates. All rights reserved. Cisco Confidential VLSM VLSM Topology Address Assignment • Using VLSM subnets, the LAN and inter-router networks can be addressed without unnecessary waste as shown in the logical topology diagram.
40 © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 11.9 Structured Design
41 © 2019, 2021 Cisco and/or its affiliates. All rights reserved. Cisco Confidential Structured Design IPv4 Network Address Planning IP network planning is crucial to develop a scalable solution to an enterprise network. • To develop an IPv4 network wide addressing scheme, you need to know how many subnets are needed, how many hosts a particular subnet requires, what devices are part of the subnet, which parts of your network use private addresses, and which use public, and many other determining factors. Examine the needs of an organization’s network usage and how the subnets will be structured. • Perform a network requirement study by looking at the entire network to determining how each area will be segmented. • Determine how many subnets are needed and how many hosts per subnet. • Determine DHCP address pools and Layer 2 VLAN pools.
42 © 2019, 2021 Cisco and/or its affiliates. All rights reserved. Cisco Confidential Structured Design Device Address Assignment Within a network, there are different types of devices that require addresses: • End user clients – Most use DHCP to reduce errors and burden on network support staff. IPv6 clients can obtain address information using DHCPv6 or SLAAC. • Servers and peripherals – These should have a predictable static IP address. • Servers that are accessible from the internet – Servers must have a public IPv4 address, most often accessed using NAT. • Intermediary devices – Devices are assigned addresses for network management, monitoring, and security. • Gateway – Routers and firewall devices are gateway for the hosts in that network. When developing an IP addressing scheme, it is generally recommended that you have a set pattern of how addresses are allocated to each type of device.
43 © 2019, 2021 Cisco and/or its affiliates. All rights reserved. Cisco Confidential Structured Design Packet Tracer – VLSM Design and Implementation Practice In this Packet Tracer, you will do the following: • Examine the Network Requirements • Design the VLSM Addressing Scheme • Assign IP Addresses to Devices and Verify Connectivity
Cisco_Packet_Tracer_Module_Addressing IPv4.pdf

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Cisco_Packet_Tracer_Module_Addressing IPv4.pdf

  • 1. Module 11: IPv4 Addressing Instructor Materials Introduction to Networks v7.0 (ITN)
  • 2. 2 © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 11.1 IPv4 Address Structure
  • 3. 3 © 2019, 2021 Cisco and/or its affiliates. All rights reserved. Cisco Confidential IPv4 Address Structure Network and Host Portions • An IPv4 address is a 32-bit hierarchical address that is made up of a network portion and a host portion. • When determining the network portion versus the host portion, you must look at the 32-bit stream. • A subnet mask is used to determine the network and host portions.
  • 4. 4 © 2019, 2021 Cisco and/or its affiliates. All rights reserved. Cisco Confidential IPv4 Address Structure The Subnet Mask • To identify the network and host portions of an IPv4 address, the subnet mask is compared to the IPv4 address bit for bit, from left to right. • The actual process used to identify the network and host portions is called ANDing.
  • 5. 5 © 2019, 2021 Cisco and/or its affiliates. All rights reserved. Cisco Confidential IPv4 Address Structure The Prefix Length • A prefix length is a less cumbersome method used to identify a subnet mask address. • The prefix length is the number of bits set to 1 in the subnet mask. • It is written in “slash notation” therefore, count the number of bits in the subnet mask and prepend it with a slash. Subnet Mask 32-bit Address Prefix Length 255.0.0.0 11111111.00000000.00000000.00000000 /8 255.255.0.0 11111111.11111111.00000000.00000000 /16 255.255.255.0 11111111.11111111.11111111.00000000 /24 255.255.255.128 11111111.11111111.11111111.10000000 /25 255.255.255.192 11111111.11111111.11111111.11000000 /26 255.255.255.224 11111111.11111111.11111111.11100000 /27 255.255.255.240 11111111.11111111.11111111.11110000 /28 255.255.255.248 11111111.11111111.11111111.11111000 /29 255.255.255.252 11111111.11111111.11111111.11111100 /30
  • 6. 6 © 2019, 2021 Cisco and/or its affiliates. All rights reserved. Cisco Confidential IPv4 Address Structure Determining the Network: Logical AND • A logical AND Boolean operation is used in determining the network address. • Logical AND is the comparison of two bits where only a 1 AND 1 produces a 1 and any other combination results in a 0. • 1 AND 1 = 1, 0 AND 1 = 0, 1 AND 0 = 0, 0 AND 0 = 0 • 1 = True and 0 = False • To identify the network address, the host IPv4 address is logically ANDed, bit by bit, with the subnet mask to identify the network address.
  • 7. 7 © 2019, 2021 Cisco and/or its affiliates. All rights reserved. Cisco Confidential IPv4 Address Structure Network, Host, and Broadcast Addresses • Within each network are three types of IP addresses: • Network address • Host addresses • Broadcast address Network Portion Host Portion Host Bits Subnet mask 255.255.255.0 or /24 255 255 255 11111111 11111111 11111111 0 00000000 Network address 192.168.10.0 or /24 192 168 10 11000000 10100000 00001010 0 00000000 All 0s First address 192.168.10.1 or /24 192 168 10 11000000 10100000 00001010 1 00000001 All 0s and a 1 Last address 192.168.10.254 or /24 192 168 10 11000000 10100000 00001010 254 11111110 All 1s and a 0 Broadcast address 192.168.10.255 or /24 192 168 10 11000000 10100000 00001010 255 11111111 All 1s
  • 8. 8 © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 11.2 IPv4 Unicast, Broadcast, and Multicast
  • 9. 9 © 2019, 2021 Cisco and/or its affiliates. All rights reserved. Cisco Confidential IPv4 Unicast, Broadcast, and Multicast Unicast • Unicast transmission is sending a packet to one destination IP address. • For example, the PC at 172.16.4.1 sends a unicast packet to the printer at 172.16.4.253.
  • 10. 10 © 2019, 2021 Cisco and/or its affiliates. All rights reserved. Cisco Confidential IPv4 Unicast, Broadcast, and Multicast Broadcast • Broadcast transmission is sending a packet to all other destination IP addresses. • For example, the PC at 172.16.4.1 sends a broadcast packet to all IPv4 hosts.
  • 11. 11 © 2019, 2021 Cisco and/or its affiliates. All rights reserved. Cisco Confidential IPv4 Unicast, Broadcast, and Multicast Multicast • Multicast transmission is sending a packet to a multicast address group. • For example, the PC at 172.16.4.1 sends a multicast packet to the multicast group address 224.10.10.5.
  • 12. 12 © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 11.3 Types of IPv4 Addresses
  • 13. 13 © 2019, 2021 Cisco and/or its affiliates. All rights reserved. Cisco Confidential Types of IPv4 Addresses Public and Private IPv4 Addresses • As defined in in RFC 1918, public IPv4 addresses are globally routed between internet service provider (ISP) routers. • However, private addresses are not globally routable. • Private addresses are common blocks of addresses used by most organizations to assign IPv4 addresses to internal hosts. • Private IPv4 addresses are not unique and can be used internally within any network. Network Address and Prefix RFC 1918 Private Address Range 10.0.0.0/8 10.0.0.0 - 10.255.255.255 172.16.0.0/12 172.16.0.0 - 172.31.255.255 192.168.0.0/16 192.168.0.0 - 192.168.255.255
  • 14. 14 © 2019, 2021 Cisco and/or its affiliates. All rights reserved. Cisco Confidential Types of IPv4 Addresses Routing to the Internet • Network Address Translation (NAT) translates private IPv4 addresses to public IPv4 addresses. • NAT is typically enabled on the edge router connecting to the internet. • It translates the internal private address to a public global IP address.
  • 15. 15 © 2019, 2021 Cisco and/or its affiliates. All rights reserved. Cisco Confidential Types of IPv4 Addresses Special Use IPv4 Addresses Loopback addresses • 127.0.0.0 /8 (127.0.0.1 to 127.255.255.254) • Commonly identified as only 127.0.0.1 • Used on a host to test if TCP/IP is operational. Link-Local addresses • 169.254.0.0 /16 (169.254.0.1 to 169.254.255.254) • Commonly known as the Automatic Private IP Addressing (APIPA) addresses or self- assigned addresses. • Used by Windows DHCP clients to self-configure when no DHCP servers are available.
  • 16. 16 © 2019, 2021 Cisco and/or its affiliates. All rights reserved. Cisco Confidential Types of IPv4 Addresses Legacy Classful Addressing RFC 790 (1981) allocated IPv4 addresses in classes • Class A (0.0.0.0/8 to 127.0.0.0/8) • Class B (128.0.0.0 /16 – 191.255.0.0 /16) • Class C (192.0.0.0 /24 – 223.255.255.0 /24) • Class D (224.0.0.0 to 239.0.0.0) • Class E (240.0.0.0 – 255.0.0.0) • Classful addressing wasted many IPv4 addresses. Classful address allocation was replaced with classless addressing which ignores the rules of classes (A, B, C).
  • 17. 17 © 2019, 2021 Cisco and/or its affiliates. All rights reserved. Cisco Confidential Types of IPv4 Addresses Assignment of IP Addresses • The Internet Assigned Numbers Authority (IANA) manages and allocates blocks of IPv4 and IPv6 addresses to five Regional Internet Registries (RIRs). • RIRs are responsible for allocating IP addresses to ISPs who provide IPv4 address blocks to smaller ISPs and organizations.
  • 18. 18 © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 11.4 Network Segmentation
  • 19. 19 © 2019, 2021 Cisco and/or its affiliates. All rights reserved. Cisco Confidential Network Segmentation Broadcast Domains and Segmentation • Many protocols use broadcasts or multicasts (e.g., ARP use broadcasts to locate other devices, hosts send DHCP discover broadcasts to locate a DHCP server.) • Switches propagate broadcasts out all interfaces except the interface on which it was received. • The only device that stops broadcasts is a router. • Routers do not propagate broadcasts. • Each router interface connects to a broadcast domain and broadcasts are only propagated within that specific broadcast domain.
  • 20. 20 © 2019, 2021 Cisco and/or its affiliates. All rights reserved. Cisco Confidential Network Segmentation Problems with Large Broadcast Domains • A problem with a large broadcast domain is that these hosts can generate excessive broadcasts and negatively affect the network. • The solution is to reduce the size of the network to create smaller broadcast domains in a process called subnetting. • Dividing the network address 172.16.0.0 /16 into two subnets of 200 users each: 172.16.0.0 /24 and 172.16.1.0 /24. • Broadcasts are only propagated within the smaller broadcast domains.
  • 21. 21 © 2019, 2021 Cisco and/or its affiliates. All rights reserved. Cisco Confidential Network Segmentation Reasons for Segmenting Networks • Subnetting reduces overall network traffic and improves network performance. • It can be used to implement security policies between subnets. • Subnetting reduces the number of devices affected by abnormal broadcast traffic. • Subnets are used for a variety of reasons including by: Location Group or Function Device Type
  • 22. 22 © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 11.5 Subnet an IPv4 Network
  • 23. 23 © 2019, 2021 Cisco and/or its affiliates. All rights reserved. Cisco Confidential Subnet an IPv4 Network Subnet on an Octet Boundary • Networks are most easily subnetted at the octet boundary of /8, /16, and /24. • Notice that using longer prefix lengths decreases the number of hosts per subnet. Prefix Length Subnet Mask Subnet Mask in Binary (n = network, h = host) # of hosts /8 255.0.0.0 nnnnnnnn.hhhhhhhh.hhhhhhhh.hhhhhhhh 11111111.00000000.00000000.00000000 16,777,214 /16 255.255.0.0 nnnnnnnn.nnnnnnnn.hhhhhhhh.hhhhhhhh 11111111.11111111.00000000.00000000 65,534 /24 255.255.255.0 nnnnnnnn.nnnnnnnn.nnnnnnnn.hhhhhhhh 11111111.11111111.11111111.00000000 254
  • 24. 24 © 2019, 2021 Cisco and/or its affiliates. All rights reserved. Cisco Confidential Subnet an IPv4 Network Subnet on an Octet Boundary (Cont.) • In the first table 10.0.0.0/8 is subnetted using /16 and in the second table, a /24 mask. Subnet Address (256 Possible Subnets) Host Range (65,534 possible hosts per subnet) Broadcast 10.0.0.0/16 10.0.0.1 - 10.0.255.254 10.0.255.255 10.1.0.0/16 10.1.0.1 - 10.1.255.254 10.1.255.255 10.2.0.0/16 10.2.0.1 - 10.2.255.254 10.2.255.255 10.3.0.0/16 10.3.0.1 - 10.3.255.254 10.3.255.255 10.4.0.0/16 10.4.0.1 - 10.4.255.254 10.4.255.255 10.5.0.0/16 10.5.0.1 - 10.5.255.254 10.5.255.255 10.6.0.0/16 10.6.0.1 - 10.6.255.254 10.6.255.255 10.7.0.0/16 10.7.0.1 - 10.7.255.254 10.7.255.255 ... ... ... 10.255.0.0/16 10.255.0.1 - 10.255.255.254 10.255.255.255 Subnet Address (65,536 Possible Subnets) Host Range (254 possible hosts per subnet) Broadcast 10.0.0.0/24 10.0.0.1 - 10.0.0.254 10.0.0.255 10.0.1.0/24 10.0.1.1 - 10.0.1.254 10.0.1.255 10.0.2.0/24 10.0.2.1 - 10.0.2.254 10.0.2.255 … … … 10.0.255.0/24 10.0.255.1 - 10.0.255.254 10.0.255.255 10.1.0.0/24 10.1.0.1 - 10.1.0.254 10.1.0.255 10.1.1.0/24 10.1.1.1 - 10.1.1.254 10.1.1.255 10.1.2.0/24 10.1.2.1 - 10.1.2.254 10.1.2.255 … … … 10.100.0.0/24 10.100.0.1 - 10.100.0.254 10.100.0.255 ... ... ... 10.255.255.0/24 10.255.255.1 - 10.2255.255.254 10.255.255.255
  • 25. 25 © 2019, 2021 Cisco and/or its affiliates. All rights reserved. Cisco Confidential Subnet an IPv4 Network Subnet within an Octet Boundary • Refer to the table to see six ways to subnet a /24 network. Prefix Length Subnet Mask Subnet Mask in Binary (n = network, h = host) # of subnets # of hosts /25 255.255.255.128 nnnnnnnn.nnnnnnnn.nnnnnnnn.nhhhhhhh 11111111.11111111.11111111.10000000 2 126 /26 255.255.255.192 nnnnnnnn.nnnnnnnn.nnnnnnnn.nnhhhhhh 11111111.11111111.11111111.11000000 4 62 /27 255.255.255.224 nnnnnnnn.nnnnnnnn.nnnnnnnn.nnnhhhhh 11111111.11111111.11111111.11100000 8 30 /28 255.255.255.240 nnnnnnnn.nnnnnnnn.nnnnnnnn.nnnnhhhh 11111111.11111111.11111111.11110000 16 14 /29 255.255.255.248 nnnnnnnn.nnnnnnnn.nnnnnnnn.nnnnnhhh 11111111.11111111.11111111.11111000 32 6 /30 255.255.255.252 nnnnnnnn.nnnnnnnn.nnnnnnnn.nnnnnnhh 11111111.11111111.11111111.11111100 64 2
  • 26. 26 © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 11.6 Subnet a Slash 16 and a Slash 8 Prefix
  • 27. 27 © 2019, 2021 Cisco and/or its affiliates. All rights reserved. Cisco Confidential Subnet a Slash 16 and a Slash 8 Prefix Create Subnets with a Slash 16 prefix • The table highlights all the possible scenarios for subnetting a /16 prefix. Prefix Length Subnet Mask Network Address (n = network, h = host) # of subnets # of hosts /17 255.255.128.0 nnnnnnnn.nnnnnnnn.nhhhhhhh.hhhhhhhh 11111111.11111111.10000000.00000000 2 32766 /18 255.255.192.0 nnnnnnnn.nnnnnnnn.nnhhhhhh.hhhhhhhh 11111111.11111111.11000000.00000000 4 16382 /19 255.255.224.0 nnnnnnnn.nnnnnnnn.nnnhhhhh.hhhhhhhh 11111111.11111111.11100000.00000000 8 8190 /20 255.255.240.0 nnnnnnnn.nnnnnnnn.nnnnhhhh.hhhhhhhh 11111111.11111111.11110000.00000000 16 4094 /21 255.255.248.0 nnnnnnnn.nnnnnnnn.nnnnnhhh.hhhhhhhh 11111111.11111111.11111000.00000000 32 2046 /22 255.255.252.0 nnnnnnnn.nnnnnnnn.nnnnnnhh.hhhhhhhh 11111111.11111111.11111100.00000000 64 1022 /23 255.255.254.0 nnnnnnnn.nnnnnnnn.nnnnnnnh.hhhhhhhh 11111111.11111111.11111110.00000000 128 510 /24 255.255.255.0 nnnnnnnn.nnnnnnnn.nnnnnnnn.hhhhhhhh 11111111.11111111.11111111.00000000 256 254 /25 255.255.255.128 nnnnnnnn.nnnnnnnn.nnnnnnnn.nhhhhhhh 11111111.11111111.11111111.10000000 512 126 /26 255.255.255.192 nnnnnnnn.nnnnnnnn.nnnnnnnn.nnhhhhhh 11111111.11111111.11111111.11000000 1024 62 /27 255.255.255.224 nnnnnnnn.nnnnnnnn.nnnnnnnn.nnnhhhhh 11111111.11111111.11111111.11100000 2048 30 /28 255.255.255.240 nnnnnnnn.nnnnnnnn.nnnnnnnn.nnnnhhhh 11111111.11111111.11111111.11110000 4096 14 /29 255.255.255.248 nnnnnnnn.nnnnnnnn.nnnnnnnn.nnnnnhhh 11111111.11111111.11111111.11111000 8192 6 /30 255.255.255.252 nnnnnnnn.nnnnnnnn.nnnnnnnn.nnnnnnhh 11111111.11111111.11111111.11111100 16384 2
  • 28. 28 © 2019, 2021 Cisco and/or its affiliates. All rights reserved. Cisco Confidential Subnet a Slash 16 and a Slash 8 Prefix Create 100 Subnets with a Slash 16 prefix Consider a large enterprise that requires at least 100 subnets and has chosen the private address 172.16.0.0/16 as its internal network address. • The figure displays the number of subnets that can be created when borrowing bits from the third octet and the fourth octet. • Notice there are now up to 14 host bits that can be borrowed (i.e., last two bits cannot be borrowed). To satisfy the requirement of 100 subnets for the enterprise, 7 bits (i.e., 27 = 128 subnets) would need to be borrowed (for a total of 128 subnets).
  • 29. 29 © 2019, 2021 Cisco and/or its affiliates. All rights reserved. Cisco Confidential Subnet a Slash 16 and a Slash 8 Prefix Create 1000 Subnets with a Slash 8 prefix Consider a small ISP that requires 1000 subnets for its clients using network address 10.0.0.0/8 which means there are 8 bits in the network portion and 24 host bits available to borrow toward subnetting. • The figure displays the number of subnets that can be created when borrowing bits from the second and third. • Notice there are now up to 22 host bits that can be borrowed (i.e., last two bits cannot be borrowed). To satisfy the requirement of 1000 subnets for the enterprise, 10 bits (i.e., 210=1024 subnets) would need to be borrowed (for a total of 128 subnets)
  • 30. 30 © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 11.7 Subnet to Meet Requirements
  • 31. 32 © 2019, 2021 Cisco and/or its affiliates. All rights reserved. Cisco Confidential Subnet to Meet Requirements Minimize Unused Host IPv4 Addresses and Maximize Subnets There are two considerations when planning subnets: • The number of host addresses required for each network • The number of individual subnets needed Prefix Length Subnet Mask Subnet Mask in Binary (n = network, h = host) # of subnets # of hosts /25 255.255.255.128 nnnnnnnn.nnnnnnnn.nnnnnnnn.nhhhhhhh 11111111.11111111.11111111.10000000 2 126 /26 255.255.255.192 nnnnnnnn.nnnnnnnn.nnnnnnnn.nnhhhhhh 11111111.11111111.11111111.11000000 4 62 /27 255.255.255.224 nnnnnnnn.nnnnnnnn.nnnnnnnn.nnnhhhhh 11111111.11111111.11111111.11100000 8 30 /28 255.255.255.240 nnnnnnnn.nnnnnnnn.nnnnnnnn.nnnnhhhh 11111111.11111111.11111111.11110000 16 14 /29 255.255.255.248 nnnnnnnn.nnnnnnnn.nnnnnnnn.nnnnnhhh 11111111.11111111.11111111.11111000 32 6 /30 255.255.255.252 nnnnnnnn.nnnnnnnn.nnnnnnnn.nnnnnnhh 11111111.11111111.11111111.11111100 64 2
  • 32. 33 © 2019, 2021 Cisco and/or its affiliates. All rights reserved. Cisco Confidential Subnet to Meet Requirements Example: Efficient IPv4 Subnetting • In this example, corporate headquarters has been allocated a public network address of 172.16.0.0/22 (10 host bits) by its ISP providing 1,022 host addresses. • There are five sites and therefore five internet connections which means the organization requires 10 subnets with the largest subnet requires 40 addresses. • It allocated 10 subnets with a /26 (i.e., 255.255.255.192) subnet mask.
  • 33. 34 © 2019, 2021 Cisco and/or its affiliates. All rights reserved. Cisco Confidential Subnet to Meet Requirements Packet Tracer – Subnetting Scenario In this Packet Tracer, you will do the following: • Design an IP Addressing Scheme • Assign IP Addresses to Network Devices and Verify Connectivity
  • 34. 35 © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 11.8 VLSM
  • 35. 36 © 2019, 2021 Cisco and/or its affiliates. All rights reserved. Cisco Confidential VLSM IPv4 Address Conservation Given the topology, 7 subnets are required (i.e, four LANs and three WAN links) and the largest number of host is in Building D with 28 hosts. • A /27 mask would provide 8 subnets of 30 host IP addresses and therefore support this topology.
  • 36. 37 © 2019, 2021 Cisco and/or its affiliates. All rights reserved. Cisco Confidential VLSM IPv4 Address Conservation (Cont.) However, the point-to-point WAN links only require two addresses and therefore waste 28 addresses each for a total of 84 unused addresses. • Applying a traditional subnetting scheme to this scenario is not very efficient and is wasteful. • VLSM was developed to avoid wasting addresses by enabling us to subnet a subnet.
  • 37. 38 © 2019, 2021 Cisco and/or its affiliates. All rights reserved. Cisco Confidential VLSM VLSM • The left side displays the traditional subnetting scheme (i.e., the same subnet mask) while the right side illustrates how VLSM can be used to subnet a subnet and divided the last subnet into eight /30 subnets. • When using VLSM, always begin by satisfying the host requirements of the largest subnet and continue subnetting until the host requirements of the smallest subnet are satisfied. • The resulting topology with VLSM applied.
  • 38. 39 © 2019, 2021 Cisco and/or its affiliates. All rights reserved. Cisco Confidential VLSM VLSM Topology Address Assignment • Using VLSM subnets, the LAN and inter-router networks can be addressed without unnecessary waste as shown in the logical topology diagram.
  • 39. 40 © 2016 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 11.9 Structured Design
  • 40. 41 © 2019, 2021 Cisco and/or its affiliates. All rights reserved. Cisco Confidential Structured Design IPv4 Network Address Planning IP network planning is crucial to develop a scalable solution to an enterprise network. • To develop an IPv4 network wide addressing scheme, you need to know how many subnets are needed, how many hosts a particular subnet requires, what devices are part of the subnet, which parts of your network use private addresses, and which use public, and many other determining factors. Examine the needs of an organization’s network usage and how the subnets will be structured. • Perform a network requirement study by looking at the entire network to determining how each area will be segmented. • Determine how many subnets are needed and how many hosts per subnet. • Determine DHCP address pools and Layer 2 VLAN pools.
  • 41. 42 © 2019, 2021 Cisco and/or its affiliates. All rights reserved. Cisco Confidential Structured Design Device Address Assignment Within a network, there are different types of devices that require addresses: • End user clients – Most use DHCP to reduce errors and burden on network support staff. IPv6 clients can obtain address information using DHCPv6 or SLAAC. • Servers and peripherals – These should have a predictable static IP address. • Servers that are accessible from the internet – Servers must have a public IPv4 address, most often accessed using NAT. • Intermediary devices – Devices are assigned addresses for network management, monitoring, and security. • Gateway – Routers and firewall devices are gateway for the hosts in that network. When developing an IP addressing scheme, it is generally recommended that you have a set pattern of how addresses are allocated to each type of device.
  • 42. 43 © 2019, 2021 Cisco and/or its affiliates. All rights reserved. Cisco Confidential Structured Design Packet Tracer – VLSM Design and Implementation Practice In this Packet Tracer, you will do the following: • Examine the Network Requirements • Design the VLSM Addressing Scheme • Assign IP Addresses to Devices and Verify Connectivity