IP ADDRESSING -PART 2 Lecture 16
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.
