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Implementing and Monitoring RIB on Cisco IOS XR Software
Prerequisites for Implementing RIB on Cisco IOS XR Software
RC-196
Cisco IOS XR Routing Configuration Guide
Prerequisites for Implementing RIB on Cisco IOS XR Software
• To use this command, you must be in a user group associated with a task group that includes the
proper task IDs. For detailed information about user groups and task IDs, see the Configuring AAA
Services on Cisco IOS XR Software module of the Cisco IOS XR System Security Configuration
Guide.
• RIB is distributed with the base Cisco IOS XR software; as such, it does not have any special
requirements for installation. The following are the requirements for base software installation:
–
Router
–
Cisco IOS XR software
–
Base package
Information About RIB Configuration
To implement the Cisco RIB feature, you must understand the following concepts:
• Overview of RIB, page RC-196
• RIB Data Structures in BGP and Other Protocols, page RC-196
• RIB Administrative Distance, page RC-197
• RIB Support for IPv4 and IPv6, page RC-197
Overview of RIB
Each routing protocol selects its own set of best routes and installs those routes and their attributes in
RIB. RIB stores these routes and selects the best ones from among all routing protocols. Those routes
are downloaded to the line cards for use in forwarding packets. The acronym RIB is used both to refer
to RIB processes and the collection of route data contained within RIB.
Within a protocol, routes are selected based on the metrics in use by that protocol. A protocol downloads
its best routes (lowest or tied metric) to RIB. RIB selects the best overall route by comparing the
administrative distance of the associated protocol.
RIB Data Structures in BGP and Other Protocols
RIB uses processes and maintains data structures distinct from other routing applications, such as Border
Gateway Protocol (BGP) and other unicast routing protocols, or multicast protocols, such as Protocol
Independent Multicast (PIM) or Multicast Source Discovery Protocol (MSDP). However, these routing
protocols use internal data structures similar to what RIB uses, and may internally refer to the data
structures as a RIB. For example, BGP routes are stored in the BGP RIB (BRIB), and multicast routes,
computed by multicast routing protocols such as PIM and MSDP, are stored in the Multicast RIB
(MRIB). RIB processes are not responsible for the BRIB and MRIB, which are handled by BGP and
multicast processes, respectively.
The table used by the line cards and RP to forward packets is called the Forwarding Information Base
(FIB). RIB processes do not build the FIBs. Instead, RIB downloads the set of selected best routes to the
FIB processes, by the Bulk Content Downloader (BCDL) process, onto each line card. FIBs are then
constructed.