RC-144

Implementing OSPF on Cisco IOS XR Software

How to Implement OSPF on Cisco IOS XR Software

•If graceful restart is enabled, the adjacency creation time of all the neighbors is saved in the system database (SysDB). The purpose for saving the creation time is so that OSPFv3 can use the original adjacency creation time to display the uptime for that neighbor after the restart.

Multicast-Intact Feature

The multicast-intact feature provides the ability to run multicast routing (PIM) when IGP shortcuts are configured and active on the router. Both OSPFv2 and IS-IS support the multicast-intact feature.

You can enable multicast-intact in the IGP when multicast routing protocols (PIM) are configured and IGP shortcuts are configured on the router. IGP shortcuts are MPLS tunnels that are exposed to IGP. The IGPs routes IP traffic over these tunnels to destinations that are downstream from the egress router of the tunnel (from an SPF perspective). PIM cannot use IGP shortcuts for propagating PIM joins because reverse path forwarding (RPF) cannot work across a unidirectional tunnel.

When you enable multicast-intact on an IGP, the IGP publishes a parallel or alternate set of equal-cost next-hops for use by PIM. These next-hops are called mcast-intactnext-hops. The mcast-intact next-hops have the following attributes:

•They are guaranteed not to contain any IGP shortcuts.

•They are not used for unicast routing but are used only by PIM to look up an IPv4 next-hop to a PIM source.

•They are not published to the FIB.

•When multicast-intact is enabled on an IGP, all IPv4 destinations that were learned through link-state advertisements are published with a set equal-cost mcast-intact next-hops to the RIB. This attribute applies even when the native next-hops have no IGP shortcuts.

•In OSPF, the max-paths (number of equal-cost next-hops) limit is applied separately to the native and mcast-intact next-hops. The number of equal cost mcast-intact next-hops is the same as that configured for the native next-hops. (In IS-IS, the behavior is slightly different.)

How to Implement OSPF on Cisco IOS XR Software

This section contains the following procedures:

•Enabling OSPF, page RC-145(required)

•Configuring Stub and Not-so-Stubby Area Types, page RC-147(optional)

•Configuring Neighbors for Nonbroadcast Networks, page RC-150(optional)

•Configuring Authentication at Different Hierarchical Levels for OSPF Version 2, page RC-155(optional)

•Controlling the Frequency that the Same LSA Is Originated or Accepted for OSPF, page RC-158(optional)

•Creating a Virtual Link with MD5 Authentication to Area 0 for OSPF, page RC-160(optional)

•Summarizing Subnetwork LSAs on an OSPF ABR, page RC-164(optional)

•Redistributing Routes from One IGP into OSPF, page RC-166(optional)

•Configuring OSPF Shortest Path First Throttling, page RC-170(optional)

•Configuring Nonstop Forwarding for OSPF Version 2, page RC-173(optional)

•Configuring OSPF Version 2 for MPLS Traffic Engineering, page RC-175(optional)

Cisco IOS XR Routing Configuration Guide

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.