What is vlsm
-There are no rules for assigning subnet identifiers within a site. Several (non-exclusive) techniques can be used:+There are no rules for the assignment of subnet identifiers within a site. Several (non-exclusive) techniques can be used such as:
-* incrementally enumerate subnets: 0001, 0002, …. This technique is easy to implement in experimental networks, but can result in a flat addressing scheme that is difficult to remember. It can be used, for example, for a subnet dedicated to servers in order to simplify writing and memorizing addresses:+* incrementally enumerate the subnets: 0001, 0002, …. This technique is easy to implement in experimental networks, but can result in a flat addressing scheme that is difficult to remember. It can be used, for example, for a subnet dedicated to servers in order to simplify the writing and memorization of addresses;
To facilitate the connection between our router and the devices (computers, cell phones, etc), all routers on the market include a DHCP server. This “Dynamic Host Configuration Protocol”, or “Dynamic Host Configuration Protocol” allows the router to configure a fixed or dynamic IP to all computers and devices that connect to it automatically without the user having to do anything to do so.
Most home routers configure IPs within the 192.168.1.x or 192.168.0.x network, a 255.255.255.255.0 subnet mask, the router’s own IP as the gateway and the DNS of the operator providing the Internet connection.
Most routers (although not all) allow the user to reserve a series of IP addresses so that these can be static, fixed, always avoiding having to manually configure the computer and that, by mistake, our IP can be assigned to another device on the network, associating its own configurations (ports, for example) and our equipment losing this configuration.
How to subnet a network
The terms “packet” and “datagram” are also often used interchangeably. Conceptually, a “packet” is the lowest-level physical unit, while “datagram” refers to the IP-level unit of data. However, in most networks they are indistinguishable because they overlap, so people often use the two terms interchangeably.
Many of the decisions involved in setting up an IP network depend on routing. In general, an IP datagram passes through numerous networks as it travels between source and destination. Let us look at a typical example:
This graphic shows three computers, 2 gateways and three networks. The networks could be Ethernet, Token Ring or any other type. Network 2 could be a point-to-point line connecting the R and S gateways.
Computer A can send datagrams to computer B directly, using network 1. However, it cannot reach computer C directly, since they are not on the same network. There are several ways to connect networks. In the graphic we assume the use of gateways (we will see other alternatives later). In this case, datagrams going from A to C must be sent through gateway R, network 2 and gateway S. All computers using TCP/IP need to be supplied with the appropriate information and algorithms so that they can know when a datagram should be sent through a gateway, and choose the appropriate gateway.
Now imagine a subnet that has 27 Application Gateway instances and one private front-end IP address. In this case, you need 33 IP addresses: 27 for the Application Gateway instances, one for the private front-end and five for internal use.
The IP addresses are assigned from the beginning of the subnet space defined for the gateway instances. As instances are created and removed due to gateway creation or escalation events, it can be difficult to understand which address is next available on the subnet. In order to determine the next address to use for a future gateway and have a contiguous addressing topic for front-end IP addresses, consider assigning front-end IP addresses from the top half of the defined subset space. For example, if my subnet address space is 10.5.5.0/24, consider setting the front-end IP address of gateways from 10.5.5.5.254 and follow with 10.5.5.253, 10.5.5.5.252, 10.5.5.251, etc. for future gateways.