Implementing Routing Policy on Cisco IOS XR Software

Information About Implementing Routing Policy

route-policy quickstart-drop

drop

end-policy

Ignore routes with specific AS numbers in the path

The following example shows the policy definition in three parts. First, the as-path-setcommand defines three regular expressions to match against an AS path. Second, the route-policycommand applies the AS path set to a route. If the AS path attribute of the route matches the regular expression defined with the as-path-setcommand, the protocol refuses the route. Third, the route policy is attached to BGP neighbor 10.0.1.2. BGP consults the policy named ignore_path_as on routes received (imported) from neighbor 10.0.1.2.

as-path-set ignore_path ios-regex '_11_', ios-regex '_22_', ios-regex '_33_'

end-set

route-policy ignore_path_as

if as-path in ignore_path then drop

else pass

endif

end-policy

router bgp 2

neighbor 10.0.1.2 address-family ipv4 unicast policy ignore_path_as in

Set community based on MED

The following example shows how the policy tests the MED of a route and modifies the community attribute of the route based on the value of the MED. If the MED value is 127, the policy adds the community 123:456 to the route. If the MED value is 63, the policy adds the value 123:789 to the community attribute of the route. Otherwise, the policy removes the community 123:123 from the route. In any case, the policy instructs the protocol to accept the route.

route-policy quickstart-med if med eq 127 then

set community (123:456) additive elseif med eq 63 then

set community (123:789) additive else

delete community in (123:123) endif

pass

end-policy

Set local preference based on community

The following example shows how the community-set named quickstart-communities defines community values. The route policy named quickstart-localpref tests a route for the presence of the communities specified in the quickstart-communities community set. If any of the community values are present in the route, the route policy sets the local preference attribute of the route to 31. In any case, the policy instructs the protocol to accept the route.

community-set quickstart-communities 987:654, 987:543,

987:321,

987:210 end-set

Cisco IOS XR Routing Configuration Guide

RC-212

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Cisco Systems IOS XR manual Ignore routes with specific AS numbers in the path, Set community based on MED, RC-212
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IOS XR specifications

Cisco Systems IOS XR is an advanced operating system designed specifically for high-performance routers and service provider networks. It serves as the backbone for many of Cisco's high-end routing platforms, enabling service providers to manage their networks with increased efficiency, flexibility, and scalability.

One of the main features of IOS XR is its modular architecture. This allows for the independent operation of various components within the OS, facilitating the deployment of new features and updates without affecting the overall stability of the system. This modularity ensures that service providers can implement rapid changes and enhancements while maintaining service continuity.

Another characteristic of IOS XR is its support for 64-bit architecture, which provides enhanced performance and the ability to manage larger amounts of data. This is particularly beneficial for service providers that deal with high traffic volumes and require robust data processing capabilities. The utilization of 64-bit technology also enables the operating system to utilize memory more efficiently, allowing for greater scalability.

IOS XR incorporates advanced technologies such as Distributed System Architecture (DSA) and Multiple Routing Instances (Merging Routes). DSA allows for the distribution of routing processes across multiple hardware resources, maximizing performance and redundancy. Multiple Routing Instances enable operators to create separate logical routing tables for different services, improving isolation and efficiency in managing network traffic.

The operating system also focuses heavily on security, featuring extensive encryption methods and access controls to safeguard network resources. IOS XR supports various authentication protocols, ensuring secure access to routers and switches. In addition, the OS includes comprehensive logging and monitoring capabilities, allowing network administrators to track activities and respond quickly to potential threats.

Another critical aspect of IOS XR is its adherence to the principles of service-oriented architecture (SOA). This approach permits the development of applications and services that can operate independently, fostering innovation and enabling service providers to tailor their offerings based on customer demands.

Ultimately, Cisco IOS XR is a powerful, reliable operating system that meets the complex needs of modern telecommunications networks. With its focus on modularity, performance, security, and scalability, it enables service providers to deliver high-quality, resilient services to their customers while efficiently managing network resources. As the industry continues to evolve, IOS XR remains a vital tool for those aiming to stay competitive in the ever-changing landscape of networking.
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