Module 11 IPv4 Addressing

Introduction to Networks v7.0 (ITN) Module 11: IPv4 Addressing This Slides is prepared by: Eng. Rawan Aljamal Cisco Certified CCNA Instructor Trainer 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. 2 IPv4 Address Structure IPv4 address is a 32-bit hierarchical address that is usually represented in dot-decimal notation, consisting of four decimal numbers, each ranging from 0 to 255, separated by dots 3 Network and Host Portions • An IPv4 address that is made up of a network portion and a host portion. • A subnet mask is used to determine the network and host portions. 4 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 The Prefix Length or CIDR notation • A prefix length is a less cumbersome method‫ طريقة أقل تعقي ا‬used to identify a subnet mask ‫ًد‬ • address. The prefix length is the number of bits set to 1 in the subnet mask. 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 7 Determining the Network: Logical AND • To identify the network address, the host IPv4 address is logically ANDed, bit by bit, with • the subnet mask to identify 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. /24 8 Network, Host, and Broadcast Addresses Within each network are three types of IP addresses: • • • Network address is the address that have all host bits equals to zeros. Host addresses is the address that have the l host bits have mix zeros and ones. Broadcast address is the address that have all host bits equal to ones Subnet mask 255.255.255.0 or /24 Network address 192.168.10.0 or /24 First address 192.168.10.1 or /24 Last address 192.168.10.254 or /24 Broadcast address 192.168.10.255 or /24 Network Portion Host Portion 255 255 255 11111111 11111111 11111111 192 168 10 11000000 10100000 00001010 192 168 10 11000000 10100000 00001010 192 168 10 11000000 10100000 00001010 192 168 10 11000000 10100000 00001010 0 00000000 0 00000000 1 00000001 254 11111110 255 11111111 Host Bits All 0s All 0s and a 1 All 1s and a 0 All 1s 9 Legacy Classful Addressing In Classful Addressing, the subnet mask is determined based on the value in the first octet of the IP address. Class Name First Octet Content in binary Network Range Network – Host configuration Subnet mask Number of hosts per network Class A 01xxxxxx 0 -127 N.H.H.H 255.0.0.0 or /8 2^24 = 16,777,216 Class B 10xxxxx 128 -191 N.N.H.H 255.255.0.0 or /16 2^16 = 65,536 Class C 110xxxxx 192 -223 N.N.N.H 255.255.255.0 or /24 2^8 = 256 Class D 1110xxxx 224-239 Reserved for Multicasting purposes Class E 1111xxxx 240-255 Reserved for experimental work 10 Legacy Classful Addressing Classful addressing wasted many IPv4 addresses. Classful address allocation was replaced with classless addressing which ignores the rules of classes (A, B, C). In classless addressing the subnet mask as well as the network and host portions are determined according to the wanted network size 11 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. 12 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. 13 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. 14 Public and Private IPv4 Addresses • • • • • Private addresses are common blocks of addresses used by most organizations to assign IPv4 addresses to internal hosts. Private addresses are not globally routable 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 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 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. DHCP (Dynamic Host Configuration Protocol) is a protocol that provides quick, automatic, and central management for the distribution of IP addresses within a network. 16 Network Segmentation (Subnetting) 17 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. 18 Problems with Large Broadcast Domains • A problem with a large broadcast domain is that these hosts can generate excessive ‫ ُم َباَلغ فيه‬broadcasts and negatively affect the network. • The solution is to reduce the size of the network to create smaller broadcast domains using subnetting. • Dividing the network address 172.16.0.0 /16 into two subnets of 200 users each: 1. 172.16.0.0 /24 2. 172.16.1.0 /24. • Broadcasts are only propagated within the smaller broadcast domains. 19 Reasons for Segmenting Networks 1. 2. 3. 4. 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 20 IPv4 Address Conservation • • • Given the topology with 192.168.1.0/24 network. 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. 21 Subnets and Subnet Masks Subnetting : Dividing the network into small networks or subnets by borrowing bits from the host bits. 22 Subnetting Formulas  To calculate the number of subnets that can be created from the bits borrowed The possible number of subnets that can be created when borrowing 1, 2, 3, 4, 5, or 6 bits. 23 Subnetting Formulas  To calculate the number of hosts that can be supported: There are two subnet addresses that cannot be assigned to a host, the network address and the broadcast address, so we must subtract 2.  Therefore, borrowing 1 host bit toward the network results in creating 2 subnets, and each subnet can have a total of 126 hosts assigned.  There are 7 host bits remaining, so the calculation is 2^7 = 128-2 = 126. This means that each of the subnets has 126 valid host addresses. 24 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. 25 IPv4 Addressing in Packet Tracer 26 Suggested Lab Work Solve the work sheet, it will help you to understand the Subnetting and VLSM concepts. Page # Activity Name 11.5.5 Subnet an IPv4 Network 11.7.5 Subnetting Scenario 11.9.3 VLSM Design and Implementation Practice 11.10.1 Design and Implement a VLSM Addressing Scheme 27