Prerequisites For Implementing Static Routes; Restrictions For Implementing Static Routes; Information About Implementing Static Routes; Static Route Functional Overview - Cisco ASR 9000 Series Routing Configuration Manual

Prerequisites for Implementing Static Routes

Prerequisites for Implementing Static Routes
You must be in a user group associated with a task group that includes the proper task IDs. The command
reference guides include the task IDs required for each command. If you suspect user group assignment is
preventing you from using a command, contact your AAA administrator for assistance.

Restrictions for Implementing Static Routes

These restrictions apply while implementing Static Routes:
• Static routing to an indirect next hop, (any prefix learnt through the RIB and may be more specific over
• Generally, a route is learnt from the AIB in the global table and is installed in the FIB. However, this

Information About Implementing Static Routes

To implement static routes you need to understand the following concepts:

Static Route Functional Overview

Networking devices forward packets using route information that is either manually configured or dynamically
learned using a routing protocol. Static routes are manually configured and define an explicit path between
two networking devices. Unlike a dynamic routing protocol, static routes are not automatically updated and
must be manually reconfigured if the network topology changes. The benefits of using static routes include
security and resource efficiency. Static routes use less bandwidth than dynamic routing protocols, and no CPU
cycles are used to calculate and communicate routes. The main disadvantage to using static routes is the lack
of automatic reconfiguration if the network topology changes.
Static routes can be redistributed into dynamic routing protocols, but routes generated by dynamic routing
protocols cannot be redistributed into the static routing table. No algorithm exists to prevent the configuration
of routing loops that use static routes.
Static routes are useful for smaller networks with only one path to an outside network and to provide security
for a larger network for certain types of traffic or links to other networks that need more control. In general,
most networks use dynamic routing protocols to communicate between networking devices but may have one
or two static routes configured for special cases.

Default Administrative Distance

Static routes have a default administrative distance of 1. A low number indicates a preferred route. By default,
static routes are preferred to routes learned by routing protocols. Therefore, you can configure an administrative
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the AIB), that is part of a local subnet requires configuring static routes in the global table indicating
the egress interfaces as next hop. To avoid forward drop, configure static routes in the global table
indicating the next-hop IP address to be the next hop.
behavior will not be replicated to leaked prefixes. Because the AIB from the global table is not present
in the VRF, the leaked FIB entry takes reference from the RIB rather than the same view as the global
table, which also relies on the AIB. This could lead to inconsistencies in forwarding behavior.
Implementing Static Routes