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. In many cases, static routes are manually configured by a

network administrator A network administrator is a person designated in an organization whose responsibility includes maintaining computer infrastructures with emphasis on local area networks (LANs) up to wide area networks (WANs). Responsibilities may vary between org ...

by adding in entries into a

routing table 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 th ...

, though this may not always be the case. Unlike

dynamic routing Dynamic routing, also called adaptive routing, is a process where a router can forward data via a different route for a given destination based on the current conditions of the communication circuits within a system. The term is most commonly asso ...

, static routes are fixed and do not change if the network is changed or reconfigured. Static routing and

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.

Uses

Static routing may have the following uses: * Static routing can be used to define an exit point from a router when no other routes are available or necessary. This is called a

default route In computer networking, the default route is a configuration of the Internet Protocol (IP) that establishes a forwarding rule for packets when no specific address of a next-hop host is available from the routing table or other routing mechanisms ...

. * Static routing can be used for small networks that require only one or two routes. This is often more efficient since a link is not being wasted by exchanging dynamic routing information. * Static routing is often used as a complement to dynamic routing to provide a failsafe backup if a dynamic route is unavailable. * Static routing is often used to help transfer routing information from one routing protocol to another (routing redistribution).

Advantages

Static routing, if used without dynamic routing, has the following advantages: * Static routing causes very little load on the CPU of the router, and produces no traffic to other routers. * Static routing leaves the network administrator with full control over the routing behavior of the network. * Static Routing is very easy to configure on small networks.

Disadvantages

Static routing can have some potential disadvantages: * Human error: In many cases, static routes are manually configured. This increases the potential for input mistakes. Administrators can make mistakes and mistype in network information, or configure incorrect routing paths by mistake. * Fault tolerance: Static routing is not fault tolerant. This means that when there is a change in the network or a failure occurs between two statically defined devices, traffic will not be re-routed. As a result, the network is unusable until the failure is repaired or the static route is manually reconfigured by an administrator. * Administrative distance: Static routes typically take precedence over routes configured with a dynamic routing protocol. This means that static routes may prevent

routing protocols A routing protocol specifies how routers communicate with each other to distribute information that enables them to select routes between nodes on a computer network. Routers perform the traffic directing functions on the Internet; data packets ...

from working as intended. A solution is to manually modify the

administrative distance 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 (low AD value) to least pref ...

.Cisco Systems (n.d)
Configuring Static Routing
accessed 5 November 2013 * Administrative overhead: Static routes must be configured on each router in the network(s). This configuration can take a long time if there are many routers. It also means that reconfiguration can be slow and inefficient. Dynamic routing on the other hand automatically propagates routing changes, reducing the need for manual reconfiguration.

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 iproute2 is a collection of userspace utilities for controlling and monitoring various aspects of networking in the Linux kernel, including routing, network interfaces, tunnels, traffic control, and network-related device drivers. iproute ...

command. The following is typed at a terminal:- root@router:~# ip route add 10.10.20.0 via 192.168.100.1

Cisco

Enterprise-level

Cisco routers Cisco Systems, Inc., commonly known as Cisco, is an American-based multinational corporation, multinational digital communications technology conglomerate (company), conglomerate corporation headquartered in San Jose, California. Cisco develo ...

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:ip route
/ref> 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: 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.Cisco Systems (2013),
What is Administrative Distance?
retrieved 12 June 2014 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.

References

{{reflist Routing