Static routing

Last updated

Static routing is a form of routing that occurs when a router uses a manually-configured routing entry, rather than information from dynamic routing traffic. [1] In many cases, static routes are manually configured by a network administrator by adding in entries into a routing table, though this may not always be the case. [2] Unlike dynamic routing, static routes are fixed and do not change if the network is changed or reconfigured. Static routing and dynamic routing are not mutually exclusive. Both dynamic routing and static routing are usually used on a router to maximise routing efficiency and to provide backups in case dynamic routing information fails to be exchanged. Static routing can also be used in stub networks, or to provide a gateway of last resort.

Contents

Uses

Static routing may have the following uses:

Advantages

Static routing, if used without dynamic routing, has the following advantages:[ citation needed ]

Disadvantages

Static can have some potential disadvantages: [3]

Example

To route IP traffic destined for the network 10.10.20.0/24 via the next-hop router with the IPv4 address of 192.168.100.1, the following configuration commands or steps can be used:

Linux

In most Linux distributions, a static route can be added using the iproute2 command. The following is typed at a terminal:- [5]

root@router:~# iprouteadd10.10.20.0via192.168.100.1 

Cisco

Enterprise-level Cisco routers are configurable using the Cisco IOS command line, rather than a web management interface.

Add a static route

The commands to add a static route are as follows: [6]

Router> enable Router# configure terminal Router(config)# ip route 10.10.20.0 255.255.255.0 192.168.100.1

Network configurations are not restricted to a single static route per destination: [6]

Router> enable Router# configure terminal Router(config)# ip route 197.164.73.0 255.255.255.0 197.164.72.2 Router(config)# ip route 197.164.74.0 255.255.255.0 197.164.72.2

Configuring administrative distance

The administrative distance can be manually (re)configured so that the static route can be configured as a backup route, to be used only if the dynamic route is unavailable. [7]

Router(config)# ip route 10.10.20.0 255.255.255.0 exampleRoute 1 254

Setting the administrative distance to 254 will result in the route being used only as a backup.

See also

Related Research Articles

The Dynamic Host Configuration Protocol (DHCP) is a network management protocol used on Internet Protocol (IP) networks for automatically assigning IP addresses and other communication parameters to devices connected to the network using a client–server architecture.

An Internet Protocol address is a numerical label such as 192.0.2.1 that is connected to a computer network that uses the Internet Protocol for communication. An IP address serves two main functions: network interface identification and location addressing.

<span class="mw-page-title-main">Router (computing)</span> Device that forwards data packets between computer networks

A router is a networking device that forwards data packets between computer networks. Routers perform the traffic directing functions between networks and on the global Internet. Data sent through a network, such as a web page or email, is in the form of data packets. A packet is typically forwarded from one router to another router through the networks that constitute an internetwork until it reaches its destination node.

Open Shortest Path First (OSPF) is a routing protocol for Internet Protocol (IP) networks. It uses a link state routing (LSR) algorithm and falls into the group of interior gateway protocols (IGPs), operating within a single autonomous system (AS).

The Routing Information Protocol (RIP) is one of the oldest distance-vector routing protocols which employs the hop count as a routing metric. RIP prevents routing loops by implementing a limit on the number of hops allowed in a path from source to destination. The largest number of hops allowed for RIP is 15, which limits the size of networks that RIP can support.

In computer networking, a routing table, or routing information base (RIB), is a data table stored in a router or a network host that lists the routes to particular network destinations, and in some cases, metrics (distances) associated with those routes. The routing table contains information about the topology of the network immediately around it.

Enhanced Interior Gateway Routing Protocol (EIGRP) is an advanced distance-vector routing protocol that is used on a computer network for automating routing decisions and configuration. The protocol was designed by Cisco Systems as a proprietary protocol, available only on Cisco routers. In 2013 Cisco decided to allow other vendors freely implement limited version of EIGRP with some of its associated features such as High Availability (HA), while withholding other EIGRP features such as EIGRP stub, needed for DMVPN and large-scale campus deployment, exclusively for themselves. Information needed for implementation was published with informational status as RFC 7868 in 2016, which did not make it into an Internet Standards Track specification and allowed Cisco to retain control of the EIGRP protocol.

A virtual local area network (VLAN) is any broadcast domain that is partitioned and isolated in a computer network at the data link layer. In this context, virtual, refers to a physical object recreated and altered by additional logic, within the local area network. VLANs work by applying tags to network frames and handling these tags in networking systems – creating the appearance and functionality of network traffic that is physically on a single network but acts as if it is split between separate networks. In this way, VLANs can keep network applications separate despite being connected to the same physical network, and without requiring multiple sets of cabling and networking devices to be deployed.

The Internetworking Operating System (IOS) is a family of proprietary network operating systems used on several router and network switch models manufactured by Cisco Systems. The system is a package of routing, switching, internetworking, and telecommunications functions integrated into a multitasking operating system. Although the IOS code base includes a cooperative multitasking kernel, most IOS features have been ported to other kernels, such as Linux and QNX, for use in Cisco products.

Dial on Demand Routing (DDR) is a routing technique where a network connection to a remote site is established only when needed. In other words, if the router tries to send out data and the connection is off, then the router will automatically establish a connection, send the information, and close the connection when no more data needs to be sent. DDR is advantageous for companies that must pay per minute for a WAN setup, where a connection is always established. Constant connections can become needlessly expensive if the company does not require a constant internet connection.

ifconfig Network administration utility

ifconfig is a system administration utility in Unix-like operating systems for network interface configuration.

<span class="mw-page-title-main">NetFlow</span> Communications protocol

NetFlow is a feature that was introduced on Cisco routers around 1996 that provides the ability to collect IP network traffic as it enters or exits an interface. By analyzing the data provided by NetFlow, a network administrator can determine things such as the source and destination of traffic, class of service, and the causes of congestion. A typical flow monitoring setup consists of three main components:

Administrative distance (AD) or route preference is a number of arbitrary unit assigned to dynamic routes, static routes and directly-connected routes. The value is used in routers to rank routes from most preferred to least preferred. When multiple paths to the same destination are available in its routing table, the router uses the route with the lowest administrative distance.

A UDP Helper Address is a special router configuration used to forward broadcast network traffic from a client machine on one subnet to a server in another subnet.

Dynamic Multipoint Virtual Private Network (DMVPN) is a dynamic tunneling form of a virtual private network (VPN) supported on Cisco IOS-based routers, and Huawei AR G3 routers, and on Unix-like operating systems.

In computer networking, CDP spoofing is a technique employed to compromise the operation of network devices that use Cisco Discovery Protocol (CDP) for discovering neighboring devices. CDP spoofing is a network security threat that can be mitigated by taking precautionary measures.

In network routing, the control plane is the part of the router architecture that is concerned with drawing the network topology, or the information in a routing table that defines what to do with incoming packets. Control plane functions, such as participating in routing protocols, run in the architectural control element. In most cases, the routing table contains a list of destination addresses and the outgoing interface(s) associated with each. Control plane logic also can identify certain packets to be discarded, as well as preferential treatment of certain packets for which a high quality of service is defined by such mechanisms as differentiated services.

Web Cache Communication Protocol (WCCP) is a Cisco-developed content-routing protocol that provides a mechanism to redirect traffic flows in real-time. It has built-in load balancing, scaling, fault tolerance, and service-assurance (failsafe) mechanisms. Cisco IOS Release 12.1 and later releases allow the use of either Version 1 (WCCPv1) or Version 2 (WCCPv2) of the protocol.

IP routing is the application of routing methodologies to IP networks. This involves not only protocols and technologies but includes the policies of the worldwide organization and configuration of Internet infrastructure. In each IP network node, IP routing involves the determination of a suitable path for a network packet from a source to its destination in an IP network. The process uses static configuration rules or dynamically obtained from routing protocols to select specific packet forwarding methods to direct traffic to the next available intermediate network node one hop closer to the desired final destination, a total path potentially spanning multiple computer networks.

In a router, route redistribution allows a network that uses one routing protocol to route traffic dynamically based on information learned from another routing protocol.

References

  1. TCP/IP Tutorial and Technical Overview (IBM RedBooks Series)
  2. "Cisco IOS Dial Technologies Configuration Guide, Release 12.2SR - Reliable Static Routing Backup Using Object Tracking [Cisco IOS Software Releases 12.2 SR]".
  3. Tetz E (n.d), Pros and Cons of Static Routing www.dummies.com, accessed 5 November 2013
  4. Cisco Systems (n.d), Configuring Static Routing, accessed 5 November 2013
  5. "16.4. Static Routes and the Default Gateway Red Hat Enterprise Linux 5".
  6. 1 2 ip route
  7. Cisco Systems (2013), What is Administrative Distance?, retrieved 12 June 2014