A routing table is a set of rules that are often viewed in tabular format, which is used to determine where data packets moving over the Internet Protocol (Internet Protocol or IP for short) will be routed. All IP-enabled devices, including routers and switches, use this tool.
Description
A routing table is a type of data file that acts like a card and is often installed on a router, network computer, or other equipment. Provides information on the various routes between devices to provide the most efficient paths for data packets.
One of the tasks of developing a tabular form is to record information on many devices with fixed memory or storage space. There is also the problem of working with the ARP cache and properly maintaining lists of available routes for the routing table. This is often called an incorrect definition of network topology. Other routing problems, such as black holes that cause inefficient delivery, should also be considered when using.
Definition
The routing table contains the information necessary to forward the packet along the optimal path to the destination. Each package contains information about its origin and purpose. When it is received, the network device checks the data and compares it with the entry in the table that provides the best match for its destination. The table then provides the device with instructions for sending the packet along the next route on the network.
Basic concepts
The basic routing table includes the following information:
- Destination: IP address of the final destination of the packet.
- Next hop: IP address to which the packet is forwarded.
- Interface: The outgoing network interface that the device should use when forwarding the packet to the next or final destination.
- Metric: assigns a cost to each available route so that you can choose the most economical route.
- Routes: includes directly connected and indirect subnets that are not connected to the device, but can be accessed through one or more transitions. Default routes are used for certain types of traffic or in the absence of information.
Routing table commands can be supported manually or dynamically. Tabular forms for static network devices do not change unless the network administrator manually changes them. In dynamic routing, devices automatically create and maintain their tables using protocols for exchanging network topology information. This data allows devices to “listen” to the network and respond to situations such as device failures and network congestion.
Windows routing tables
A routing and remote access service is a set of network services in the Windows Server family that allows a server to perform the services of a conventional router. RRAS includes an application programming interface (API) that facilitates the development of applications and processes for administering a range of network services.
Windows Server 2000, 2003, and 2008 are integrated with various network services and specific APIs that enable the server to provide data transfer and network routing functions. The routing service, which converts Windows Server into a virtual / software router, is one of these programming interfaces. Applications cover a wide range of services that can be centrally managed by the server's domain controller.
Scheme
Building a routing table gives a remote user access to the internal network through a connection to a secure virtual private network (VPN). This connectivity can be deployed using a typical IP-based VPN over the Internet.
Services included with the routing and remote access services:
- remote access;
- remote server remote access;
- VPN remote access tank
- IP router for connecting subnets;
- network address translation services;
- other services related to the router;
- Dial-up and VPN router with on-demand dialing.
Specification
The routing table is present on all IP nodes, it stores information about networks and how they can be achieved (directly or indirectly). Since all IP nodes perform some form of routing, this data is not exclusive to IP routers. Any node loading the TCP / IP protocol has its own tabular form. There are a number of default entries according to the host configuration, and additional entries can be entered manually through TCP / IP utilities or dynamically through interaction with routers.
When an IP packet needs to be forwarded, the table is used to determine:
- IP addresses of forwarding or next hop;
- interface to be used for forwarding.
Input types
The entry in the routing table contains the following information in the order presented:
- The network identifier, or destination corresponding to the route, can be a network identifier based on a class, subnet, or supernet, or the IP address for the host route.
- The netmask is used to match the destination address with the network identifier.
- The IP address of the next hop.
- Interface — Indicates which network interface is used to forward the IP packet.
- Metric - a number used to indicate the cost of the route, so you can choose the best route between the possible. The common use of the metric is to indicate the number of hops (crossed by routers) on the network identifier.
Routing table elements can be used to store the following types of routes:
- Directly attached network identifiers - routes for network identifiers that are connected directly.
- Remote Network Identifiers — Routes for network identifiers that are not directly connected but are accessible to other routers.
- Host Routes — A route to a specific IP address. Host routes allow routing based on IP address. For host routes, the network identifier is the IP address of the specified host, and the netmask is 255.255.255.255.
- The default route is for use when no more specific network identifier or host route is found. The default routing network identifier is 0.0.0.0 with a netmask of 0.0.0.0.
The routing table uses static and dynamic Internet protocol or IP addresses to identify devices and works with the ARP cache that contains these addresses. A table is usually called a resource for finding the next transition or subsequent route for a data packet. Static or dynamic routes are compared to find the best way to transfer data.