user manual
Table Of Contents
- Cisco IOS XR Routing Configuration Guide
- Contents
- Preface
- Document Revision History
- Obtaining Documentation
- Documentation Feedback
- Cisco Product Security Overview
- Obtaining Technical Assistance
- Obtaining Additional Publications and Information
- Implementing BGP on Cisco IOS XR Software
- Contents
- Prerequisites for Implementing BGP on CiscoIOSXR Software
- Information About Implementing BGP on CiscoIOSXR Software
- BGP Functional Overview
- BGP Router Identifier
- BGP Default Limits
- BGP Validation of Local Next-Hop Addresses
- BGP Configuration
- No Default Address Family
- Routing Policy Enforcement
- Table Policy
- Update Groups
- BGP Best Path Algorithm
- Multiprotocol BGP
- Route Dampening
- BGP Routing Domain Confederation
- BGP Route Reflectors
- Default Address Family for show Commands
- How to Implement BGP on CiscoIOSXR Software
- Enabling BGP Routing
- Configuring a Routing Domain Confederation for BGP
- Resetting eBGP Session Immediately Upon Link Failure
- Logging Neighbor Changes
- Adjusting BGP Timers
- Changing the BGP Default Local Preference Value
- Configuring the MED Metric for BGP
- Configuring BGP Weights
- Tuning the BGP Best Path Calculation
- Indicating BGP Backdoor Routes
- Configuring Aggregate Addresses
- Redistributing iBGP Routes into IGP
- Redistributing Prefixes into Multiprotocol BGP
- Configuring BGP Route Dampening
- Applying Policy When Updating the Routing Table
- Setting BGP Administrative Distance
- Configuring a BGP Neighbor Group
- Configuring a BGP Neighbor
- Configuring a Route Reflector for BGP
- Configuring BGP Route Filtering by Route Policy
- Disabling Next Hop Processing on BGP Updates
- Configuring BGP Community and Extended-Community Filtering
- Configuring Software to Store Updates from a Neighbor
- Disabling a BGP Neighbor
- Resetting Neighbors Using BGP Dynamic Inbound Soft Reset
- Resetting Neighbors Using BGP Outbound Soft Reset
- Resetting Neighbors Using BGP Hard Reset
- Clearing Caches, Tables and Databases
- Displaying System and Network Statistics
- Monitoring BGP Update Groups
- Configuration Examples for Implementing BGP on CiscoIOSXR Software
- Where to Go Next
- Additional References
- Implementing IS-IS on Cisco IOS XR Software
- Contents
- Prerequisites for Implementing IS-IS on CiscoIOSXR Software
- Restrictions for Implementing IS-IS on CiscoIOSXR Software
- Information About Implementing IS-IS on CiscoIOSXR Software
- IS-IS Functional Overview
- Key Features Supported in the CiscoIOSXR IS-IS Implementation
- IS-IS Configuration Grouping
- IS-IS Interfaces
- Multitopology Configuration
- IPv6 Routing and Configuring IPv6 Addressing
- Limit LSP Flooding
- Maximum LSP Lifetime and Refresh Interval
- Overload Bit Configuration During Multitopology Operation
- Single-Topology IPv6 Support
- Multitopology IPv6 Support
- Nonstop Forwarding
- Multi-Instance IS-IS
- Multiprotocol Label Switching Traffic Engineering
- Overload Bit on Router
- Default Routes
- Attached Bit on an IS-IS Instance
- Multicast-Intact Feature
- How to Implement IS-IS on CiscoIOSXR Software
- Enabling IS-IS and Configuring Level 1 or Level 2 Routing
- Configuring Single Topology for IS-IS
- Configuring Multitopology for IS-IS
- Controlling LSP Flooding for IS-IS
- Configuring Nonstop Forwarding for IS-IS
- Configuring Authentication for IS-IS
- Configuring MPLS Traffic Engineering for IS-IS
- Tuning Adjacencies for IS-IS on Point-to-Point Interfaces
- Setting SPF Interval for a Single-Topology IPv4 and IPv6 Configuration
- Enabling Multicast-Intact for IS-IS
- Customizing Routes for IS-IS
- Configuration Examples for Implementing IS-IS on CiscoIOSXR Software
- Where to Go Next
- Additional References
- Implementing OSPF on Cisco IOS XR Software
- Contents
- Prerequisites for Implementing OSPF on CiscoIOSXR Software
- Information About Implementing OSPF on CiscoIOSXR Software
- OSPF Functional Overview
- Key Features Supported in the CiscoIOSXR OSPF Implementation
- Comparison of CiscoIOSXR OSPFv3 and OSPFv2
- Importing Addresses into OSPFv3
- OSPF Hierarchical CLI and CLI Inheritance
- OSPF Routing Components
- OSPF Process and Router ID
- Supported OSPF Network Types
- Route Authentication Methods for OSPF Version 2
- Neighbors and Adjacency for OSPF
- Designated Router (DR) for OSPF
- Default Route for OSPF
- Link-State Advertisement Types for OSPF Version 2
- Link-State Advertisement Types for OSPFv3
- Virtual Link and Transit Area for OSPF
- Route Redistribution for OSPF
- OSPF Shortest Path First Throttling
- Nonstop Forwarding for OSPF Version 2
- Load Balancing in OSPF Version 2 and OSPFv3
- Graceful Restart for OSPFv3
- Multicast-Intact Feature
- How to Implement OSPF on CiscoIOSXR Software
- Enabling OSPF
- Configuring Stub and Not-so-Stubby Area Types
- Configuring Neighbors for Nonbroadcast Networks
- Configuring Authentication at Different Hierarchical Levels for OSPF Version 2
- Controlling the Frequency that the Same LSA Is Originated or Accepted for OSPF
- Creating a Virtual Link with MD5 Authentication to Area 0 for OSPF
- Summarizing Subnetwork LSAs on an OSPF ABR
- Redistributing Routes from One IGP into OSPF
- Configuring OSPF Shortest Path First Throttling
- Configuring Nonstop Forwarding for OSPF Version 2
- Configuring OSPF Version 2 for MPLS Traffic Engineering
- Verifying OSPF Configuration and Operation
- Configuring OSPFv3 Graceful Restart
- Enabling Multicast-Intact for OSPFv2
- Configuration Examples for Implementing OSPF on CiscoIOSXR Software
- CiscoIOSXR for OSPF Version 2 Configuration: Example
- CLI Inheritance and Precedence for OSPF Version 2: Example
- MPLS TE for OSPF Version 2: Example
- ABR with Summarization for OSPFv3: Example
- ABR Stub Area for OSPFv3: Example
- ABR Totally Stub Area for OSPFv3: Example
- Route Redistribution for OSPFv3: Example
- Virtual Link Configured Through Area 1 for OSPFv3: Example
- Virtual Link Configured with MD5 Authentication for OSPF Version 2: Example
- Where to Go Next
- Additional References
- Implementing and Monitoring RIB on CiscoIOSXR Software
- Contents
- Prerequisites for Implementing RIB on CiscoIOSXR Software
- Information About RIB Configuration
- How to Deploy and Monitor RIB
- Configuration Examples for RIB Monitoring
- Output of show route Command: Example
- Output of show route backup Command: Example
- Output of show route best-local Command: Example
- Output of show route connected Command: Example
- Output of show route local Command: Example
- Output of show route longer-prefixes Command: Example
- Output of show route next-hop Command: Example
- Where to Go Next
- Additional References
- Implementing Routing Policy on Cisco IOS XR Software
- Implementing Static Routes on Cisco IOS XR Software
- Index
Implementing OSPF on Cisco IOS XR Software
Information About Implementing OSPF on Cisco IOS XR Software
RC-142
Cisco IOS XR Routing Configuration Guide
Modes of Graceful Restart Operation
The two operational modes that a router can be in for this feature are restart mode and helper mode.
Restart mode occurs when the OSPFv3 process is doing a graceful restart. Helper mode refers to the
neighbor routers that continue to forward traffic on established OSPFv3 routes while OSPFv3 is
restarting on a neighboring router.
Restart Mode
When the OSPFv3 process starts up, it determines whether it must attempt a graceful restart. The
determination is based on whether graceful restart was previously enabled. (OSPFv3 does not attempt a
graceful restart upon the first-time startup of the router.) When OSPFv3 graceful restart is enabled, it
changes the purge timer in the RIB to a non-zero value. See Configuring OSPFv3 Graceful Restart,
page RC-181, for descriptions of how to enable and configure the Graceful Restart feature.
During a graceful restart, the router does not populate OSPFv3 routes in the RIB. It tries to bring up full
adjacencies with the fully-adjacent neighbors that OSPFv3 had before the restart. Eventually, the
OSPFv3 process indicates to the RIB that it has converged either for the purpose of terminating the
graceful restart (for any reason) or because it has completed the graceful restart.
The following are general details about restart mode. More detailed information on behavior and certain
restrictions and requirements appear in the Graceful Restart Requirements and Restrictions section.
• If the OSPFv3 attempts a restart too soon after the most recent restart, the OSPFv3 process is most
likely crashing repeatedly, so the new graceful restart stops running. To control the period between
allowable graceful restarts, use the graceful-restart interval command. A description of how to set
this time period appears in the section Configuring the Minimum Time Required Between Restarts,
page RC-183.
• When OSFPv3 starts a graceful restart with the first interface that comes up, a timer starts running
to limit the duration (or lifetime) of the graceful restart. You can configure this period with the
graceful-restart lifetime command. On each interface that comes up, a grace LSA (type 11) is
flooded to indicate to the neighboring routers that this router is attempting graceful restart. The
neighbors enter into helper mode.
• The designated router and backup designated router check of the hello packet received from the
restarting neighbor is bypassed because it might not be valid.
Helper Mode
Helper mode is enabled by default. When a (helper) router receives a grace LSA (type 11) from a router
that is attempting a graceful restart, the following events occur:
• If helper mode has been disabled through the graceful-restart helper disable command, the router
drops the LSA packet.
• If helper mode is enabled, the router enters helper mode if all of the following conditions are met.
–
The local router itself is not attempting a graceful restart.
–
The local (helping) router has full adjacency with the sending neighbor.
–
The value of lsage (link state age) in the received LSA is less than the requested grace period.
–
The sender of the grace LSA is the same as the originator of the grace LSA.