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Classless Interdomain Routing (CIDR) | Computer Networks - Computer Science Engineering (CSE) PDF Download

Classess Interdomain Routing (CIDR)
Way of describing IP ranges sharing a common bit prefix,we write IP/length, where IP is the first address from the range,and length is the length of the common prefix
 

Example We want to describe IP addresses whose binary representation starts with
10011100.00010001.00000100.0010

First IP address from the range:10011100.00010001.00000100.00100000=156.17.4.32 prefix length = 28
Description =156.17.4.32/28

CIDR used mostly for describing single networks 156.17.4.32/28 denotes all the addresses between 156.17.4.32 and 156.17.4.47

  • First address in the network is reserved (network address)
  • Last address is also reserved: broadcast address.
  • Remaining ones can be assigned to computers

CIDR allows creating hierarchie s of networks and subnetworks Note:Top block received directly from IANA.
208.128.0.0/11
Note:
208.130.29.33/32= range consisting of one IPaddress = single computer, not rea lly a network.

Classless Interdomain Routing (CIDR) | Computer Networks - Computer Science Engineering (CSE)

We add/xx (called subnet mask) to all IP addresses.

Example:
156.17.4.32/28: denotes whole network 156.17.4.33/28: the first comput er in this network 156.17.4.46/28: the last computer in this network 156.17.4.47/28: broadcast addres s of this network

If you assign address 10.0.0.1 to a network card, it will be interpreted as10.0.0.1/8 Why?
Reason stems from pre-CIDR IP classes

If the first IP bit is 0, assume sub net mask /8(A class network). Example:6.0.0.0/8
If the first IP bits are 10, assume subnet mask/16(B class network). Example:156.17.0.0/16
If the first IP bits are 110, assume subnet mask/24(B classnetwork). Example:200.200.200.0/24
Network 127.0.0.0/8
Interface lo (loopback)

By connecting with any computer from this network (usually with127.0.0.1), you connect with yourself. Application: it is possible to write, test and use network programs without the network.

Reserved ranges of IP addresses
Packet with such addresses should not be passed through routers.Can be used in local networks (same addresses in different networks).
Ranges:

10.0.0.0/8 (one A class network); 172.16.0.0/12 (16 B class networks); 192.168.0.0/16 (256 C class networks)
If computers with private IP addresses want to communicate with the outside world, the connecting router has to perform NetworkAddress Translation(NAT).

The document Classless Interdomain Routing (CIDR) | Computer Networks - Computer Science Engineering (CSE) is a part of the Computer Science Engineering (CSE) Course Computer Networks.
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FAQs on Classless Interdomain Routing (CIDR) - Computer Networks - Computer Science Engineering (CSE)

1. What is Classless Interdomain Routing (CIDR)?
Ans. Classless Interdomain Routing (CIDR) is a method of IP address allocation and routing. It allows for the division of IP address space into smaller subnets, which can then be assigned to networks as needed. CIDR replaces the older class-based addressing system, which allocated IP addresses in fixed blocks of different sizes.
2. How does CIDR improve IP address allocation?
Ans. CIDR improves IP address allocation by allowing for more efficient utilization of the available address space. With CIDR, IP addresses can be assigned in smaller increments, known as subnets, based on the actual number of devices or networks requiring addresses. This reduces address wastage and allows for more flexibility in network design.
3. What is a CIDR notation?
Ans. CIDR notation is a compact representation of IP addresses and their associated subnet masks. It is commonly used in CIDR to specify the network address and the number of significant bits in the subnet mask. The notation consists of the IP address followed by a slash ("/") and the number of bits in the subnet mask. For example, 192.168.0.0/24 represents a network with a subnet mask of 255.255.255.0.
4. How does CIDR affect routing?
Ans. CIDR greatly simplifies routing by allowing for the aggregation of multiple IP address blocks into a single route entry. This reduces the size of routing tables and improves the efficiency of routing protocols. With CIDR, routers can summarize multiple smaller subnets into larger ones, reducing the number of entries in the routing table and improving overall network performance.
5. Can CIDR be used with both IPv4 and IPv6?
Ans. Yes, CIDR can be used with both IPv4 and IPv6. It was initially introduced for IPv4 to address the growing need for more efficient IP address allocation. However, CIDR principles can also be applied to IPv6, allowing for the efficient allocation and routing of IPv6 addresses. CIDR notation is used in both IPv4 and IPv6 to represent network addresses and subnet masks.
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