IPv4 Addressing - CIDR (Classless Inter-Domain Routing) ============================================================ .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **What is CIDR?** CIDR (Classless Inter-Domain Routing) is a method for allocating IP addresses and routing IP packets, replacing the older class-based system by using variable-length subnet masking (VLSM). .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **Why is CIDR useful?** CIDR allows for more efficient allocation of IP addresses and helps reduce routing table size by enabling route aggregation (supernetting). .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **How it works?** CIDR uses a suffix (e.g., /24) to indicate how many bits are used for the network portion of the address. This allows flexible subnetting and efficient IP space utilization. .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **Where is CIDR used?** CIDR is used in IP address allocation by ISPs, routing within and between organizations, and internet backbone routing to aggregate prefixes. .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **Which OSI layer does this protocol belong to?** CIDR operates at the Network Layer (Layer 3) as it deals with IP addressing and routing. .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **Is CIDR Windows specific?** No, CIDR is not Windows specific. It is a general IP addressing method supported by all operating systems. .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **Is CIDR Linux specific?** No, CIDR is not Linux specific. It is supported universally across all platforms that use IP networking. .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **Which Transport Protocol is used by CIDR?** CIDR is not tied to any transport protocol. It affects IP routing, which works with both TCP and UDP, among others. .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **Which Port is used by CIDR?** CIDR does not use any ports. It is a method of IP address representation and routing, not a service or application. .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **Is CIDR using client-server model?** No, CIDR is not a communication protocol but an addressing scheme. It does not follow the client-server model. .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **What does the CIDR notation /16 mean?** It means the first 16 bits of the IP address are the network portion, allowing for flexible subnetting within that range. .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **How does CIDR improve IP address allocation?** CIDR eliminates fixed class boundaries, allowing IP blocks of any size, reducing wasted IP addresses. .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **What is route aggregation in CIDR?** Route aggregation (or supernetting) combines multiple IP routes into a single routing entry to simplify routing tables. .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **How does CIDR affect routing tables?** By aggregating routes, CIDR reduces the number of entries, improving router efficiency and scalability. .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **What is a subnet mask in CIDR?** The subnet mask determines which portion of an IP address refers to the network and which to the host. .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **How to calculate the number of hosts in a CIDR block?** Number of hosts = 2^(32 - prefix length) - 2 (excluding network and broadcast addresses). .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **What is the difference between CIDR and traditional classful addressing?** CIDR allows variable-length subnet masks, unlike fixed class A, B, or C network sizes in classful addressing. .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **How does CIDR help with IPv4 exhaustion?** CIDR enables efficient IP allocation, slowing the depletion of IPv4 address space. .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **Is CIDR applicable to IPv6?** Yes, IPv6 uses CIDR notation extensively for subnetting and routing. .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **Can CIDR blocks overlap?** Overlapping CIDR blocks can cause routing conflicts and should be avoided. .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **What is a supernet?** A supernet is a larger network formed by aggregating multiple smaller networks using CIDR. .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **How does CIDR notation look for IPv6?** IPv6 CIDR notation is similar, e.g., 2001:db8::/32, indicating the prefix length in bits. .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **What tools can help calculate CIDR ranges?** Various online calculators and command-line tools (like `ipcalc`) assist in CIDR calculations. .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **Is CIDR compatible with NAT (Network Address Translation)?** Yes, CIDR blocks are commonly used in NAT configurations. .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **How does CIDR impact firewall rules?** Firewalls use CIDR notation to define IP address ranges for access control. .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **What happens if CIDR notation is incorrect?** Incorrect CIDR can cause routing issues, misconfigured networks, or unreachable hosts. .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **Can CIDR be used in private networks?** Yes, CIDR is widely used to subnet private IP address ranges efficiently. .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **Does CIDR affect DNS?** CIDR itself doesn't affect DNS, but efficient IP allocation can improve DNS management. .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow **Is CIDR supported in cloud environments?** Yes, cloud providers use CIDR for virtual network subnetting and routing. .. panels:: :container: container pb-4 :column: col-lg-12 p-2 :card: shadow Topics in this section, * :ref:`Learnings in this section ` * :ref:`Terminology ` * :ref:`Version Info ` * :ref:`RADIUS Version&IEEE Details ` * :ref:`RADIUS Basic Setup on Ubuntu using IPv4 ` * :ref:`RADIUS Basic Setup on Ubuntu using IPv6 ` * :ref:`RADIUS Protocol Packet Details ` * :ref:`RADIUS Usecases ` * :ref:`RADIUS Basic Features ` * :ref:`Reference links ` .. _RADIUS_step1: .. tab-set:: .. tab-item:: Learnings in this section * In this section, you are going to learn .. _RADIUS_step2: .. tab-set:: .. tab-item:: Terminology * Terminology .. _RADIUS_step3: .. tab-set:: .. tab-item:: Version Info * Version Info .. _RADIUS_step5: .. tab-set:: .. tab-item:: RADIUS Version&RFC Details * rfc details .. _RADIUS_step18: .. tab-set:: .. tab-item:: RADIUS Basic Setup on Ubuntu using IPv4 * setup .. _RADIUS_step19: .. tab-set:: .. tab-item:: RADIUS Basic Setup on Ubuntu using IPv6 * setup .. _RADIUS_step6: .. tab-set:: .. tab-item:: RADIUS Protocol Packet Details * packet details .. _RADIUS_step7: .. tab-set:: .. tab-item:: RADIUS Usecases * usecases .. _RADIUS_step8: .. tab-set:: .. tab-item:: RADIUS Basic Features * features .. _RADIUS_step17: .. tab-set:: .. tab-item:: Reference links * Reference links