Cisco Systems IOS XR manual IS-IS Functional Overview, IS-IS Configuration Grouping, RC-85

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Implementing IS-IS on Cisco IOS XR Software

Information About Implementing IS-IS on Cisco IOS XR Software

IS-IS Functional Overview

Small IS-IS networks are typically built as a single area that includes all routers in the network. As the network grows larger, it may be reorganized into a backbone area made up of the connected set of all Level 2 routers from all areas, which is in turn connected to local areas. Within a local area, routers know how to reach all system IDs. Between areas, routers know how to reach the backbone, and the backbone routers know how to reach other areas.

The IS-IS routing protocol supports the configuration of backbone Level 2 and Level 1 areas and the necessary support for moving routing information between the areas. Routers establish Level 1 adjacencies to perform routing within a local area (intra-area routing). Routers establish Level 2 adjacencies to perform routing between Level 1 areas (interarea routing).

For Cisco IOS XR software, each IS-IS instance can support either a single Level 1 or Level 2 area, or one of each. By default, all IS-IS instances automatically support Level 1 and Level 2 routing. You can change the level of routing to be performed by a particular routing instance using the is-typecommand.

Key Features Supported in the Cisco IOS XR IS-IS Implementation

The Cisco IOS XR implementation of IS-IS conforms to the IS-IS Version 2 specifications detailed in RFC 1195 and the IPv6 IS-IS functionality based on the Internet Engineering Task Force (IETF) IS-IS Working Group draft-ietf-isis-ipv6.txt document.

The following list outlines key features supported in the Cisco IOS XR implementation:

Improved configuration syntax and enhanced show commands

Single topology IPv6

Multitopology

Nonstop forwarding (NSF), both Cisco proprietary and IETF

Three-way handshake

Mesh groups

Multiple IS-IS instances

Configuration of a broadcast medium connecting two networking devices as a point-to-point link

IS-IS Configuration Grouping

Cisco IOS XR groups all of the IS-IS configuration in router configuration mode, including the portion of the interface configurations associated with IS-IS. The grouping makes the configuration process clearer, and eliminates some of the clutter in the global interface stanza. To display the IS-IS configuration in its entirety, use the show isis interface command.

The command output displays the running configuration for all configured IS-IS instances, including the interface assignments and interface attributes.

Cisco IOS XR Routing Configuration Guide

RC-85

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Contents Corporate Headquarters Cisco IOS XR Routing Configuration GuideCisco IOS XR Routing Configuration Guide N T E N T S RC-iv Enabling BGP RoutingStandards RC-80 MIBs MIBs RC-vii Cisco IOS XR for Ospf Version 2 Configuration ExampleRC-viii Output of show route backup Command Example RC-201RC-ix Recursive Static Routes RC-249RC-x Revision Date Change Summary Document Revision HistoryCisco.com Obtaining DocumentationProduct Documentation DVD Ordering DocumentationDocumentation Feedback Reporting Security Problems in Cisco ProductsCisco Product Security Overview XiiiXiv Obtaining Technical AssistanceCisco Technical Support & Documentation Website Obtaining Additional Publications and Information Submitting a Service RequestDefinitions of Service Request Severity Xvi Implementing BGP on Cisco IOS XR Software ContentsRC-2 BGP Functional OverviewRC-3 BGP Default LimitsBGP Router Identifier Configuration Modes BGP ConfigurationBGP Validation of Local Next-Hop Addresses RC-4Global Address Family Configuration Mode Router Configuration ModeNeighbor Configuration Mode Neighbor Address Family Configuration ModeRC-6 Configuration TemplatesRC-7 Template Inheritance RulesRC-8 RC-9 RC-10 RC-11 Template InheritanceShow bgp neighbors RC-12 Show bgp af-groupRC-13 Show bgp session-groupRC-14 Show bgp neighbor-groupRC-15 No Default Address FamilyRC-16 Routing Policy EnforcementRC-17 BGP Update Generation and Update Groups Update GroupsBGP Update Group Table PolicyRC-19 Comparing Pairs of PathsRC-20 Order of ComparisonsRC-21 Multiprotocol BGPBest Path Change Suppression Incongruent Unicast and Multicast Routes RC-22RC-23 Route DampeningBGP Route Reflectors BGP Routing Domain ConfederationMinimizing Flapping RC-24Three Fully Meshed iBGP Speakers RC-25More Complex BGP Route Reflector Model RC-26RC-27 How to Implement BGP on Cisco IOS XR SoftwareDefault Address Family for show Commands RC-28 Enabling BGP RoutingPrerequisites Restrictions Command or Action PurposeExample RC-29RC-30 As a BGP peerRC-31 Configuring a Routing Domain Confederation for BGPRC-32 RC-33 Resetting eBGP Session Immediately Upon Link FailureRC-34 Adjusting BGP TimersLogging Neighbor Changes RC-35 Changing the BGP Default Local Preference ValueRC-36 Configuring the MED Metric for BGPRC-37 RC-38 Configuring BGP WeightsRC-39 Tuning the BGP Best Path CalculationRC-40 Path the least desirable pathRC-41 Indicating BGP Backdoor RoutesRC-42 RC-43 Configuring Aggregate AddressesRC-44 Redistributing iBGP Routes into IGPRC-45 RC-46 Redistributing Prefixes into Multiprotocol BGPRC-47 To be redistributed into BGPRC-48 Configuring BGP Route DampeningRC-49 RC-50 RC-51 RC-52 Applying Policy When Updating the Routing TableRC-53 Setting BGP Administrative DistanceRC-54 RC-55 Configuring a BGP Neighbor GroupRC-56 RC-57 Bytes for the BGP bufferRC-58 Configuring a BGP NeighborRC-59 RC-60 Configuring a Route Reflector for BGPRC-61 RC-62 Configuring BGP Route Filtering by Route PolicyRC-63 RC-64 Disabling Next Hop Processing on BGP UpdatesRC-65 Configuring BGP Community and Extended-Community FilteringRC-66 RC-67 Configuring Software to Store Updates from a NeighborRC-68 RC-69 Disabling a BGP NeighborRC-70 RC-71 Resetting Neighbors Using BGP Dynamic Inbound Soft ResetResetting Neighbors Using BGP Outbound Soft Reset RC-72 Resetting Neighbors Using BGP Hard ResetRC-73 Clearing Caches, Tables and DatabasesDisplaying System and Network Statistics RC-74 Performance-statistics keyword displaysRC-75 Monitoring BGP Update GroupsRC-76 Enabling BGP ExampleRC-77 Displaying BGP Update Groups ExampleRC-78 BGP Neighbor Configuration ExampleBGP Confederation Example RC-79 Where to Go NextBGP Route Reflector Example Related Documents Additional ReferencesStandards MIBsRFCs Technical AssistanceDescription Link RC-81RC-82 RC-83 Implementing IS-IS on Cisco IOS XR SoftwareRC-84 RC-85 IS-IS Configuration GroupingIS-IS Functional Overview IPv6 Routing and Configuring IPv6 Addressing Multitopology ConfigurationIS-IS Interfaces Limit LSP FloodingMesh Group Configuration Overload Bit Configuration During Multitopology OperationMaximum LSP Lifetime and Refresh Interval Single-Topology IPv6 SupportRC-88 Multitopology IPv6 SupportNonstop Forwarding Multi-Instance IS-IS Multiprotocol Label Switching Traffic EngineeringOverload Bit on Router RC-89Multicast-Intact Feature Default RoutesAttached Bit on an IS-IS Instance RC-90RC-91 How to Implement IS-IS on Cisco IOS XR SoftwareEnabling IS-IS and Configuring Level 1 or Level 2 Routing RC-92 RC-93 Configuring Single Topology for IS-ISRC-94 Ipv4 address address mask orRC-95 Specifying the ipv6 address ipv6-prefix /prefix-lengthRC-96 See the Single-Topology IPv6 Support section onRC-97 Level-2-only adjacenciesRC-98 Configuring Multitopology for IS-ISRC-99 RC-100 RC-101 RC-102 Controlling LSP Flooding for IS-ISRC-103 Max-lsp-lifetime commandRC-104 LSP was not received and subsequently resendsRC-105 RC-106 Configuring Nonstop Forwarding for IS-ISRC-107 RC-108 Configuring Authentication for IS-ISRC-109 RC-110 Configuring Mpls Traffic Engineering for IS-ISPrerequisite RC-111 RC-112 RC-113 Tuning Adjacencies for IS-IS on Point-to-Point InterfacesRC-114 To all interfacesRC-115 RC-116 Command or Action PurposeRC-117 RC-118 Enabling Multicast-Intact for IS-ISSummary Steps RC-119 Customizing Routes for IS-ISRC-120 RC-121 Instance 2 routes into its Level 1 areaRC-122 Configuring Single-Topology IS-IS for IPv6 ExampleRC-123 Configuring Multitopology IS-IS for IPv6 ExampleRC-124 RC-125 RC-126 RC-127 Implementing Ospf on Cisco IOS XR SoftwareRC-128 Information About Implementing Ospf on Cisco IOS XR SoftwareRC-129 Ospf Functional OverviewRC-130 Importing Addresses into OSPFv3 Comparison of Cisco IOS XR OSPFv3 and OSPFv2Ospf Hierarchical CLI and CLI Inheritance RC-131RC-132 Ospf Routing ComponentsAutonomous Systems Backbone Area AreasStub Area Not-so-Stubby Area NssaRouters Ospf Process and Router IDArea Border Routers ABR Autonomous System Boundary Routers AsbrPlain Text Authentication Route Authentication Methods for Ospf VersionMD5 Authentication Supported Ospf Network TypesNeighbors and Adjacency for Ospf Authentication StrategiesDesignated Router DR for Ospf Key RolloverLink-State Advertisement Types for Ospf Version Default Route for OspfLink-State Advertisement Types for OSPFv3 RC-137RC-138 Virtual Link and Transit Area for OspfRC-139 Route Redistribution for OspfOspf Shortest Path First Throttling RC-140 Nonstop Forwarding for Ospf VersionRC-141 Load Balancing in Ospf Version 2 and OSPFv3Graceful Restart for OSPFv3 RC-142 Helper ModeModes of Graceful Restart Operation RC-143 Graceful Restart Requirements and RestrictionsRC-144 How to Implement Ospf on Cisco IOS XR SoftwareRC-145 Enabling OspfRC-146 RC-147 Configuring Stub and Not-so-Stubby Area TypesRC-148 RC-149 Default-information-originate, and no-summaryRC-150 Configuring Neighbors for Nonbroadcast NetworksRC-151 RC-152 RC-153 RC-154 RC-155 RC-156 Message-digest-key key-idmd5 key clear key encrypted keyRC-157 RC-158 OspfRC-159 Default is 1 secondRC-160 RC-161 RC-162 Section on page RC-138RC-163 RC-164 Summarizing Subnetwork LSAs on an Ospf ABRExamples RC-165 RC-166 Redistributing Routes from One IGP into OspfRC-167 RC-168 Another routing domainRC-169 RC-170 Configuring Ospf Shortest Path First ThrottlingRC-171 RC-172 RC-173 Configuring Nonstop Forwarding for Ospf VersionRC-174 RC-175 Configuring Ospf Version 2 for Mpls Traffic EngineeringRC-176 Mpls traffic-eng area area-idRC-177 RP/0/RP0/CPU0router# show route ospf 1 RC-178RC-179 Sample Output for the show ospf mpls traffic-eng CommandRC-180 Verifying Ospf Configuration and OperationRC-181 Configuring OSPFv3 Graceful RestartRC-182 Configuring the Maximum Lifetime of a Graceful RestartEnabling Graceful Restart RC-183 Configuring the Minimum Time Required Between RestartsRC-184 Configuring the Helper Level of the RouterRC-185 Displaying the State of the Graceful Restart FeatureDisplaying Information About Graceful Restart RC-186 Enabling Multicast-Intact for OSPFv2RC-187 RC-188 Cisco IOS XR for Ospf Version 2 Configuration ExampleCisco IOS XR Software Configuration RC-189 CLI Inheritance and Precedence for Ospf Version 2 ExampleABR with Summarization for OSPFv3 Example Mpls TE for Ospf Version 2 ExampleABR Stub Area for OSPFv3 Example RC-190ABR Totally Stub Area for OSPFv3 Example Virtual Link Configured Through Area 1 for OSPFv3 ExampleRoute Redistribution for OSPFv3 Example RC-191RC-192 RC-193 MIBsRC-194 RC-195 Implementing and Monitoring RIB on Cisco IOS XR SoftwareOverview of RIB Information About RIB ConfigurationRIB Data Structures in BGP and Other Protocols RC-196Protocol Administrative Distance Default RIB Administrative DistanceRIB Support for IPv4 and IPv6 RC-197Verifying RIB Configuration Using the Routing Table How to Deploy and Monitor RIBVerifying Networking and Routing Problems RC-198RC-199 RC-200 Configuration Examples for RIB MonitoringOutput of show route Command Example Output of show route best-local Command Example Output of show route backup Command ExampleOutput of show route connected Command Example Output of show route local Command ExampleRC-202 Output of show route longer-prefixes Command ExampleOutput of show route next-hop Command Example RC-203 Cisco IOS XR Multicast Command Reference, ReleaseRC-204 RC-205 Implementing Routing Policy on Cisco IOS XR SoftwareInformation About Implementing Routing Policy Prerequisites for Implementing Routing PolicyRouting Policy Language Routing Policy Language OverviewNames Routing Policy Language StructureSets RC-207Named Set Form As-path-setInline Set Form RC-208Extcommunity-set Community-setNamed Form RC-209RC-210 Prefix-setInline Form Routing Policy Language Usage Routing Policy Language ComponentsPass policy RC-211Set community based on MED Ignore routes with specific AS numbers in the pathSet local preference based on community RC-212Policy Definitions Routing Policy Configuration BasicsPersistent Remarks RC-213RC-214 ParameterizationRC-215 Semantics of Policy ApplicationBoolean Operator Precedence RC-216 When Attributes Are ModifiedMultiple Modifications of the Same Attribute RC-217 Default Drop DispositionControl Flow Range Checking Policy VerificationIncomplete Policy and Set References RC-218Remark Policy StatementsAttached Policy Modification Verification of Attribute Comparisons and ActionsRC-220 DispositionRC-221 ActionRC-222 Boolean ConditionsRC-223 Attach PointsApply RC-224 BGP Policy Attach PointsAggregation RC-225 Default OriginateDampening RC-226 Neighbor ExportNeighbor Import RC-227 NetworkRedistribute RC-228 Show bgpRC-229 Table PolicyBGP Attributes and Operators RC-230 Attribute Match SetImport Export Aggregation Redistribution Prepend as-path Ospf Policy Attach PointsSet med igp-cost SuppressRC-232 OSPFv3 Policy Attach PointsOspf Attributes and Operators RC-233 OSPFv3 Attributes and OperatorsRC-234 IS-IS Policy Attach PointsIS-IS Attributes and Operators Attached Policy Modification Editing Routing Policy Configuration ElementsNonattached Policy Modification RC-235RC-236 Editing Routing Policy Configuration Elements Using the CLIRC-237 How to Implement Routing PolicyDefining a Route Policy RC-238 Attaching a Routing Policy to a BGP NeighborRC-239 Enters address family configuration modeRC-240 Modifying a Routing Policy Using the Microemacs EditorRC-241 Routing Policy Definition ExampleRC-242 Simple Inbound Policy ExampleRC-243 Modular Inbound Policy ExampleRC-244 Routing Policy Language Commands on Cisco IOS XR SoftwareRC-245 RC-246 RC-247 SoftwareRC-248 Default Administrative DistanceStatic Route Functional Overview RC-249 Directly Connected RoutesRecursive Static Routes Fully Specified Static Routes Configuring a Static RouteFloating Static Routes RC-250RC-251 Configuring a Floating Static RouteRC-252 RC-253 Changing the Maximum Number of Allowable Static RoutesRC-254 Configuring Traffic Discard Example Configuration ExamplesConfiguring a Fixed Default Route Example Configuring a Floating Static Route ExampleRC-256 RC-257 D ERC-258 RC-259 RC-260 RC-261 IS-IS RC-90RC-262 MD5RC-263 RFC 2328, Ospf VersionRC-264 RC-265 RC-266
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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.