![]() ![]() There are two static routes to the same destination (172.31.10.0/24) on R1. This is deployed with the use of static routes that point to the primary link and the use of floating static routes that point to the backup link. The backup link is only used if the primary link fails. The link between serial port 2/0 on R1 to serial port 2/0 on R2 is the backup link. The host 10.100.1.1 is used as an example of an internet host. With this configuration, the primary link is the link between serial port 1/0 on R1 to serial port 1/0 on R2 for traffic to and from the host 172.31.10.1 to the internet. In this example, the host makes a connection to remote internet host 10.100.1.1: With the network configuration illustrated in this image, one host 172.31.10.1 has connectivity to the internet. This example describes the use of floating static routes and illustrates the need to both specify the outbound interface and the next hop address with the static route command. The addition of the alternate interface enables the static route installation to become more deterministic. If there is the possibility the interface with the next hop goes down and the next hop would become reachable through a recursive route, then specify both the next hop IP address and the alternate interface through which the next hop can be found. But the remote next hop address and the interface to which the remote next hop recurses can be specified. There is no need to specify the directly-connected next hop address. Only the directly connected next hop address is specified, but this is not recommended for the reasons described in this document. When the next hop address is specified on a directly-connected interface, the router does not perform ARP for each destination address. Therefore, this kind of static route is not recommended. This static route type, especially if it is used by many packets to many different destination subnets, can cause high processor use and a very large ARP cache (along with memory allocation failures). With this type of configuration, a router performs Address Resolution Protocol (ARP) on the Ethernet for every destination the router finds through the default route because the router considers all these destinations to be directly connected to Ethernet 0. An example of such a static route is: ip route 0.0.0.0 0.0.0.0 Ethernet0. ![]() This configuration is not recommended because when the static route points to an interface and has no next hop information, the router considers each host within the range of the route to be directly connected through that interface. The route is inserted into the routing table only when the interface is active. If configured to point a static route to an interface, do not specify the next hop IP address. Static Route to Interface without Next Hop IP Address Note: An administrative distance of 255 is considered unreachable, and static routes with an administrative distance of 255 are never entered into the routing table. It is installed in the routing table only when the dynamically learned route disappears. ![]() To configure a static route that is overridden by an EIGRP route, specify an administrative distance that is greater than 170 for the static route.Ī static route with a high administrative distance is called a floating static route. ![]() For example, Enhanced Interior Gateway Routing Protocol (EIGRP)-derived routes have a default administrative distance of 90 for internal routes and 170 for external routes. When the administrative distance is increased to a value greater than the dynamic routing protocol, the static route can be a safety net when dynamic routing fails. Static routes are used for a variety of reasons and are often used when there is no dynamic route to the destination IP address, or to override the dynamically learned route.īy default, static routes have an administrative distance of one, which gives them precedence over routes from any dynamic routing protocol. Conventionsįor more information on document conventions, refer to Cisco Technical Tips Conventions. If your network is live, ensure that you understand the potential impact of any command. All of the devices used in this document started with a cleared (default) configuration. The information in this document was created from the devices in a specific lab environment. This document is not restricted to specific software and hardware versions. There are no specific requirements for this document. This document describes static routes and uses a problem scenario to demonstrate when it is desirable to specify how to reach the next hop IP address. ![]()
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