IP ADDRESSING -PART 2​ Lecture 16

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NETWORK ADDRESS​

10.1.1.0/24 and using subnet mask of 255.255.255.0 ​ A network address will have all zeros in the host portion of the IP address.​

EXERCISE CALCULATE CIDR SUBNET MASK.​

255.255.248.0​ -21 255.255.255.224----------------------​ 255.255.240.0​ ​ Start from left to right.​ 255.255.248 <- what numbers from left to right make up the number 248​ 128 64 32 16 8 4 2 1 -128+64+32+16+8=248​ 1 1 1 1 1 0 0 0 ​ => 1111111111.11111111.11111000.00000000 - Count the number of 1's ​

TYPICAL HOST ADDRESS IN NETWORK​

A typical host address will have 0s and 1s in the host portion of the address which will uniquely identify a host.​

ASSIGNMENT OF IP ADDRESSES​​

Both IPv4 and IPv6 addresses are managed by the Internet Assigned Numbers Authority (IANA) (http://www.iana.org). ​ The IANA manages and allocates blocks of IP addresses to the Regional Internet Registries (RIRs).​ RIRs are responsible for allocating IP addresses to ISPs who in turn provide IPv4 address blocks to organizations and smaller ISPs. ​

EXERCISES - GIVEN A CIDR SUBNET MASK​

Calculate Network address given the following IP address with CIDR subnet mask 172.16.1.15/20?​ ​ ​ Four Steps:​ Identify Subnet Mask in binary.​ Identify Network ID​ Identify Broadcast Address​ Identify First and Last Address​ ​ ​ ​

CLASS B (128 - 191)​

Class B (128.0.0.0 /16 - 191.255.0.0 /16) ​ Designed to support the needs of moderate to large size networks with up to approximately 65,000 host addresses. ​ It used a fixed /16 prefix with the two high-order octets to indicate the network address and the remaining two octets for host addresses. ​ The most significant two bits of the high-order octet must be 10 creating over 16,000 networks. ​ i.e 10111111.1111111111 = 2^14 = 16,384 networks/sub networks​ 2 ^16 - hosts = 65, 536 hosts​

CLASS C (192 - 223)​

Class C (192.0.0.0 /24 - 223.255.255.0 /24) ​ Designed to support small networks with a maximum of 254 hosts.​ It used a fixed /24 prefix with the first three octets to indicate the network and the remaining octet for the host addresses. ​ The most significant three bits of the high-order octet must be 110 creating over 2 million possible networks. ​ i.e. 110NNNNN.NNNNNNNN.NNNNNNNN = 2^21 =2,097,152​ 2^8 = hosts = 256​

CLASS D..CLASS E​

Class D multicast block consisting of 224- 239​ Class E experimental address block consisting of 240 - 255​

CLASSLESS SYSTEM​

Classful addressing was abandoned in the late 1990s for the newer and current classless addressing system (CIDR). ​ However, there are still classful remnants in networks today. ​

NETWORK, HOST, BROADCAST​

Each network address contains (or identifies) host address range and a broadcast address.​ With each octet containing 8 bits, the range of numbers within each octet is 0 to 255 as 2ˆ8 is 256 which provides us with 256 values ranging from 0 to 255.​ We identify network addresses, host addresses and broadcast addresses within this range of 0 to 255.​

FIRST HOST ADDRESS OF NETWORK 10.1.1.0​

First host address of network is network address plus 1.​ So network address 10.1.1.0 plus 1 is equal to 10.1.1.1 which is the first host address of the network. ​ Normally assigned to router.​

ASSIGNMENT OF IP ADDRESSES​​

For a company or organization to support network hosts, such as web servers accessible from the Internet, that organization must have a block of public addresses assigned.​ Remember that public addresses must be unique, and use of these public addresses is regulated and allocated to each organization separately. ​

CLASS A (0- 126) SUBNET MASK 255.0.0.0 ​

For example , 1.0.0.1, or 126.0.1.1​ Designed to support extremely large networks with more than 16 million host addresses. ​ It used a fixed /8 prefix with the first octet to indicate the network address.​ The remaining three octets for host addresses. ​ All class A addresses required that the most significant bit of the high-order octet be a zero creating a total of 128 possible class A networks. ​ i.e. 01111111 - 2^7 = 128 networks​ 2 ^24 =16,777,216 hosts​ ​

LEGACY CLASSFUL ADDRESSING​​

In 1981, Internet IPv4 addresses were assigned using classful addressing as defined in RFC 790, Assigned Numbers. ​ The RFC divided the ranges into specific classes called:​ Class A​ Class B​ Class C​ Class D​ Class E​ ​

LAST HOST ADDRESS​

Last host address is the broadcast address minus 1.​ So if the broadcast address is 10.1.1.255 then the last host address is 10.1.1.254.​

NETWORK ADDRESSES​

Looking at the /24 tells us that 24 bits are available to identify the network address.​ What is the significance with 24 bits?​

IPV6 NEXT......​

The IETF knew that CIDR was only a temporary solution and that a new IP protocol would have to be developed to accommodate the rapid growth in the number of Internet users.​ In 1994, the IETF began its work to find a successor to IPv4, which eventually became IPv6.​

IPV6 LEADING THE WAY!​

The depletion of IPv4 address space is the motivating factor for moving to IPv6. ​ Each IPv6 address has 128 bits versus the 32 bits in an IPv4 address. ​ IPv6 addresses are written using hexadecimal, as opposed to dotted decimal in IPv4​ Each hexadecimal number requires 4 bits - there are 32 hexadecimal numbers in total. Therefore 32 x 4 requires 128 bits for each address.​

CLASSFUL SYSTEM​

The problem was that Classful Addressing wasted a great deal of addresses and exhausted the availability of IPv4 addresses. ​ Not all organizations' requirements fit well into one of these three classes. ​ For example, a company that had a network with 260 hosts would need to be given a class B address with more than 65,000 addresses wasting 64,740 addresses.​ ​

CLASSLESS INTER-DOMAIN ROUTING (CIDR)​

The system in use today is referred to as classless addressing. ​ The formal name is Classless Inter-Domain Routing (CIDR, pronounced "cider").​ In 1993, the IETF created a new set of standards that allowed service providers to allocate IPv4 addresses on any address bit boundary (prefix length) instead of only by a class A, B, or C address. ​ This was to help delay the depletion and eventual exhaustion of IPv4 addresses.​ Classless Inter-Domain Routing is based on variable-length subnet masking (VLSM), which allows a network to be divided into variously sized subnets/networks, providing the opportunity to size a network more appropriately for local needs. ​ ​

BROADCAST ADDRESS OF NETWORK​

What is a broadcast address used for? ​ It is used by a network to send out messages to all devices on a network.​ A message sent to a broadcast address is received by all devices of a network.​ All networks have a broadcast address, where all the hosts bits are set to 1s.​ It's the last IP address of the network.​


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