IPv4 Address

Not only is VLSM able to conserve IPv4 Address, it is also a more efficient way of using available address space.

Router uses the subnet mask (32-bit number in the same format to #IPv4 Address) to distinguish the network, the subnet and the host address space. It has a consecutive 1s starting from the most significant bits (MSB) followed by 0s. The former represents the network bits, the latter shows the host bits. Currently, there are two ways to do subnetting:

Socket Programming aims to connect two computers or processes by specifying with socket, which is a pair of IPv4 Address# and port number#. By establishing a socket, both of them could communicate in duplex mode or both directions, in and out, using Internet Protocol Suite (TCP/IP)#. However, in socket programming, we usually define two entity: server and client. Server as the sender who send the messages, client as the receiver who receive and/or process the messages.

Note: If the IPv4 Address is a string with dotted format, we can translate it to 32 bit network address with the function inet_addr. Vice versa, we can get an IPv4 address string with dotted format from a network address with the function inet_ntoa.

RIP is a #classful #Distance Vector Routing Protocol that use hop count as metric to find out the routing path. The underlying #algorithm used is the Bellman-Ford Algorithm. If the metric of route is larger than 15, RIP will count it as unreachable. Routing updates are done via broadcast IP address. It can only run on IPv4 networks, in order to run IPv6 one needs to deploy RIPng (RIP next generation) instead. There is a classless implementation of RIP: RIP version 2 (RIPv2)#.

The process of forwarding the packet from its received port to the outgoing port is called switching. Despite the naming, Router will immediately drop the packet when it can’t figure the destination in its routing table maintained by itself. Otherwise, it will simply modify the destination Media Access Control Address (MAC) (the next-hop, can be another Router or the final destination) in the packet without touching the IP Address which defines the final destination. Though the primary forwarding decision will be based on the Routing Table# or routing information, assuming there is a mapping of logical address to its interface or port. If there is no path defined in the routing table to where the packet should be forwarded to, Router will redirect it to a default route if set (usually 0.0.0.0 in IPv4 Address and ::/0 in IPv6 Address), or simply discards it and sends Internet Control Message Protocol (ICMP)# Unreachable message to the source. Additionally, we can divide a physical interface into at most 65,535 logical interfaces using the command interface {interface-name} {interface}.{subinterface}. This is particularly useful in Virtual LAN (VLAN) routing.

The functionality of RARP is the exact reverse of Address Resolution Protocol (ARP), that is to map Media Access Control Address (MAC)# to IPv4 Address#. It is especially useful for a diskless host to obtain a valid IP address from its server.

Regional Internet Registry is an organisation whose responsible for the #202206151453 assignment to regional area. There are five regional registries, each corresponding to different geographical areas.

OSPF is a #Layer 3 #classless #Link-State Routing Protocol developed by Internet Engineering Task Force (IETF)# where its metric is an arbitrary value called cost (defined by RFC 2328). In Cisco, the cost calculated using bandwidth. It is secure, scalable and provides fast Convergence#. It supports both IPv4 and IPv6. The implementation of OSPF varies from vendor to vendor.

NAT is a #202206151453 technology where public addresses can be mapped to private addresses in the local network.

MAC address is a manufacturer-allocated ID number attached to a device (a computer or a network device such as 202207061800). It is permanent and unique, unlike 202206151453, meaning you can identify a specific device across the network by referring to its MAC address. An example to the MAC address: 89-F1-C3-28-3A-FF.

Service is a component from #202201291535 that help #202201311630 to fixate a permanent 202206151453#. It also act as a load balancer between nodes.

IP is the underlying protocol used by World Wide Web (WWW) to connect other computers over the network which is included in the #Internet Protocol Suite (TCP/IP). It is considered as #Network Layer protocol according to #Open Systems Interconnection (OSI) Model. Currently, it has two versions: IPv4# and IPv6#.

IGMP is an #Internet Protocol Suite (TCP/IP) protocol used by hosts and adjacent Routers# to establish multicast IPv4 Address# group memberships.

IS-IS is a #classless #Link-State Routing Protocol which has wide adoption by Internet Service Provider (ISP)#. It is a rather harden protocol to used as the attacker couldn’t break into a network routing with IS-IS using other Routing Protocol. It is available for both IPv4# and IPv6#.

IPv6 Address is a 128-bit #IP Address intended to replace the existing #IPv4 Address. It is possible to give every user on the Earth multiple global IP addresses without worrying the eventuality of running out of them. This allows true peer-to-peer networking among hosts.

IPsec is an #Network Layer security framework for secure communications over Internet Protocol (IP)# network. This means it could protect every application or Protocol#, including those that are security-ignorant (doesn’t design around security), running on top of IP (IPv4 or IPv6#, however, both of them are not compatible to each other). It is common having it to have secure access over the Internet, extranet and intranet connectivity with partners or just to enhance the security especially in electronic commerce. It provides Authentication#, Confidentiality#, and key management (secure key exchanges) services.

The security architecture of IPsec is defined by RFC 4301 which includes the need of tunnel/transport mode and SA with database implementation. Further standardisation are done in RFC 2401, RFC 2402, RFC 2406, and RFC 2408, which makes IPsec mandatory in #IPv6 Address and optional in IPv4 Address (which needs additional application). IPsec’s implementation must support four cases of Security Association (SA)#:

We can get the subnet bits if the give subnet mask is larger than the default. Remember, the total bits used for #IPv4 Address is 32 bits. We know that it is composed of 2 parts: network mask bits and host bits. Thus, the following formulae:

e2e occurs between the original source and the final destination, that is the encryption is happened in either Application Layer#, Presentation Layer#, Transport Layer# or Network Layer#. This implies that they have the shared keys. e2e only concerns about the encryption of the user data. If user’s privacy and security is desirable, then e2e is preferred. However, due to the translation limit when jumping between different network technology such as IPv4# and IPv6#, the data sent must be decrypted and then be transformed to an understandable form. This could be a huge compromise.

DHCP is a protocol used for automatic #IPv4 Address assignment. Using this protocol, the network will be able to allot an available IP address to a Network Device# upon requested. It saves up network administrative costs and conserves IP address space.

One can find a device by using either 202206151451# or 202206151453#.

To define a Default Route in Cisco Internetwork Operating System (IOS)#, use the command ip route and assign two quad zeros# (0.0.0.0) to it with an interface’s IP address or name.

CIDR is an effective method of IP Address# allocation especially for IPv4 Address developed by Internet Engineering Task Force (IETF) which utilises the prefix or the subnet mask. There is no default subnet mask for a network, instead it relies on Variable-Length Subnet Masking (VLSM)#. That being said, for CIDR to be deployed, the network must be contiguous, that is having the same network mask (the prefix must be larger than the default mask).

BGPv4 is a widely adopted #Exterior Gateway Protocols (EGP) by Internet Service Provider (ISP) which is available for both IPv4 Address and IPv6 Address)

The basic unit for Automaton Controller is Automation Job. It consists of project (collection of 202204272036# with 202208131616# or within the Automation Controller instance), credential such as CyberArk and Vault and 202204272043# which composed of 202206151453#, username, and access method (202205251209, 202205191908, API). Automation Job could be defined in a Job Template.

Inventory is a list of nodes, where #202204272036 run against, managed by #202204272021. Ansible has a default inventory file /etc/ansible/hosts but it could be changed using the option -i. We could create multiple groups that can contain multiple hosts either in domain name or 202206151453# within an inventory.

ARP is responsible for mapping IPv4 Address# to Media Access Control Address (MAC)#. See Reverse Address Resolution Protocol (RARP) for the reverse mapping. Typically, it is used on broadcast networks such as Ethernet#, Token Ring, and FDDI.

Publicly assignable #IPv4 Address are divided into 5 classes to accommodate the increasing demands. See the table below: