Cisco IOS XR Routing Configuration Guide, Release 3.2
Implementing RIB on Cisco IOS XR Software
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Table Of Contents

Implementing and Monitoring RIB on Cisco IOS XR Software

Contents

Prerequisites for Implementing RIB on Cisco IOS XR Software

Information About RIB Configuration

Overview of RIB

RIB Data Structures in BGP and Other Protocols

RIB Administrative Distance

RIB Support for IPv4 and IPv6

How to Deploy and Monitor RIB

Verifying RIB Configuration Using the Routing Table

Verifying Networking and Routing Problems

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

Related Documents

Standards

MIBs

RFCs

Technical Assistance


Implementing and Monitoring RIB on Cisco IOS XR Software

Routing Information Base (RIB) is a distributed collection of information about routing connectivity among all nodes of a network.

Each router maintains a RIB containing the routing information for that router. RIB stores the best routes from all routing protocols that are running on the system.

This module describes the tasks you need to perform to implement and monitor RIB on your Cisco IOS XR network.

Note For more information about RIB on the Cisco IOS XR software and complete descriptions of RIB commands listed in this module, see the "Related Documents" of this module. To locate documentation for other commands that might appear during the execution of a configuration task, search online in the Cisco IOS XR software master command index.

Feature History for Implementing and Monitoring RIB on Cisco IOS XR Software

Release
Modification

Release 2.0

This feature was introduced on the Cisco CRS-1.

Release 3.0

No modification.

Release 3.2

Support was added for the Cisco XR 12000 Series Router.


Contents

•Prerequisites for Implementing RIB on Cisco IOS XR Software

•Information About RIB Configuration

•How to Deploy and Monitor RIB

•Configuration Examples for RIB Monitoring

•Where to Go Next

•Additional References

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

•RIB Data Structures in BGP and Other Protocols

•RIB Administrative Distance

•RIB Support for IPv4 and IPv6

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.

RIB Administrative Distance

Forwarding is done based on the longest prefix match. If you are forwarding a packet destined to 10.0.2.1, you prefer 10.0.2.0/24 over 10.0.0.0/16 because the mask /24 is longer (and more specific) than a /16.

Routes from different protocols that have the same prefix and length are chosen based on administrative distance. For instance, the Open Shortest Path First (OSPF) protocol has an administrative distance of 110, and the Intermediate System-to-Intermediate System (IS-IS) protocol has an administrative distance of 115. If IS-IS and OSPF both download 10.0.1.0/24 to RIB, RIB would prefer the OSPF route because OSPF has a lower administrative distance. Administrative distance is used only to choose between multiple routes of the same length.

The default administrative distances for the common protocols are shown in Table 2.

Table 2 Default Administrative Distances

Protocol
Administrative Distance Default

Connected or local routes

0

Static routes

1

External BGP routes

20

OSPF routes

110

IS-IS routes

115

Internal BGP routes

200


The administrative distance for some routing protocols (for instance IS-IS, OSPF, and BGP) can be changed. See the protocol-specific documentation for the proper method to change the administrative distance of that protocol.

Note Changing the administrative distance of a protocol on some but not all routers can lead to routing loops and other undesirable behavior. Doing so is not recommended.

RIB Support for IPv4 and IPv6

In Cisco IOS XR software, RIB tables support multicast and unicast routing.

The default routing table for Cisco IOS XR RIB are the unicast and the multicast-unicast RIB tables for IPv4 and IPv6 routing, respectively. For multicast routing, routing protocols insert unicast routes into the multicast-unicast RIB table. Multicast protocols then use the information to build multicast routes (which in turn are stored in the MRIB). See the multicast documentation for more information on using and configuring multicast.

RIB processes ipv4_rib and ipv6_rib run on the RP card. If process placement functionality is available and supported by multiple RPs in the router, RIB processes can be placed on any available node.

How to Deploy and Monitor RIB

To deploy and monitor RIB, you must understand the following concepts:

•Verifying RIB Configuration Using the Routing Table (required)

•Verifying Networking and Routing Problems (required)

Verifying RIB Configuration Using the Routing Table

This task verifies the RIB configuration to ensure that RIB is running on the RP and functioning properly by checking the routing table summary and details.

SUMMARY STEPS

1. show route [afi-all | ipv4 | ipv6] [unicast | multicast | safi-all] summary

2. show route [protocol [process-id]] [afi-all | ipv4 | ipv6] [unicast | multicast | safi-all] [ip-address [mask]]

DETAILED STEPS

 
Command or Action
Purpose

Step 1 

show route [afi-all | ipv4 | ipv6] [unicast | multicast | safi-all] summary

Example:

RP/0/RP0/CPU0:router# show route summary

Displays route summary information on the specified routing table.

•The default table summarized is the IPv4 unicast routing table.

Step 2 

show route [protocol [process-id]] [afi-all | ipv4 | ipv6] [unicast | multicast | safi-all] [ip-address [mask]]

Example:

RP/0/RP0/CPU0:router# show route ipv4 unicast

Displays more detailed route information on the specified routing table.

•This command is usually issued with an IP address or other optional filters to limit its display. Otherwise, it displays all routes from the default IPv4 unicast routing table, which can result in an extensive list, depending on the configuration of the network.

Verifying Networking and Routing Problems

This task verifies the operation of the routes between nodes.

SUMMARY STEPS

1. show route [protocol [instance]] [afi-all | ipv4 | ipv6] [unicast | multicast | safi-all] [ip-address [mask]]

2. show route [afi-all | ipv4 | ipv6] [unicast | multicast | safi-all] backup [ip-address]

3. show route [afi-all | ipv4 | ipv6] [unicast | multicast | safi-all] best-local ip-address

4. show route [afi-all | ipv4 | ipv6] [unicast | multicast | safi-all] connected

5. show route [afi-all | ipv4 | ipv6] [unicast | multicast | safi-all] local [interface]

6. show route [afi-all | ipv4 | ipv6] [unicast | multicast | safi-all] ip-address mask longer-prefixes

7. show route [afi-all | ipv4 | ipv6] [unicast | multicast | safi-all] next-hop ip-address

DETAILED STEPS

 
Command or Action
Purpose

Step 1 

show route [protocol [instance]] [afi-all | ipv4 | ipv6] [unicast | multicast | safi-all] [ip-address [mask]]

Example:

RP/0/RP0/CPU0:router# show route list list1 bgp aspo ipv4 unicast 192.168.111/8

Displays the current routes in RIB.

Step 2 

show route [afi-all | ipv4 | ipv6] [unicast | multicast | safi-all] backup [ip-address]

Example:

RP/0/RP0/CPU0:router# show route ipv4 unicast backup 192.168.111/8

Displays backup routes in RIB.

Step 3 

show route [afi-all | ipv4 | ipv6] [unicast | multicast | safi-all] best-local ip-address

Example:

RP/0/RP0/CPU0:router# show route ipv4 unicast best-local 192.168.111/8

Displays the best-local address to use for return packets from the given destination.

Step 4 

show route [afi-all | ipv4 | ipv6] [unicast | multicast | safi-all] connected

Example:

RP/0/RP0/CPU0:router# show route ipv4 unicast connected

Displays the current connected routes of the routing table.

Step 5 

show route [afi-all | ipv4 | ipv6] [unicast | multicast | safi-all] local [interface]

Example:

RP/0/RP0/CPU0:router# show route ipv4 unicast local

Displays local routes for receive entries in the routing table.

Step 6 

show route [afi-all | ipv4 | ipv6] [unicast | multicast | safi-all] ip-address mask longer-prefixes

Example:

RP/0/RP0/CPU0:router# show route ipv4 unicast 192.168.111/8 longer-prefixes

Displays the current routes in RIB that share a given number of bits with a given network.

Step 7 

show route [afi-all | ipv4 | ipv6] [unicast | multicast | safi-all] next-hop ip-address

Example:

RP/0/RP0/CPU0:router# show route ipv4 unicast next-hop 192.168.1.34

Displays the next hop gateway or host to a destination address.

Configuration Examples for RIB Monitoring

RIB is not configured separately for the Cisco IOS XR system. RIB computes connectivity of the router with other nodes in the network based on input from the routing protocols. RIB may be used to monitor and troubleshoot the connections between RIB and its clients, but it is essentially used to monitor routing connectivity between the nodes in a network. This section contains displays from the show commands used to monitor that activity. The following sample output is provided:

•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

Output of show route Command: Example

The following is sample output from the show route command when entered without an address: 

RP/0/RP0/CPU0:router# show route

Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP

       O - OSPF, IA - OSPF inter area, N1 - OSPF NSSA external type 1

       N2 - OSPF NSSA external type 2, E1 - OSPF external type 1

       E2 - OSPF external type 2, E - EGP, i - ISIS, L1 - IS-IS level-1

       L2 - IS-IS level-2, ia - IS-IS inter area

       su - IS-IS summary null, * - candidate default

       U - per-user static route, o - ODR, L - local

Gateway of last resort is 172.23.54.1 to network 0.0.0.0

C    10.2.210.0/24 is directly connected, 1d21h, Ethernet0/1/0/0

L    10.2.210.221/32 is directly connected, 1d21h, Ethernet0/1/1/0

C    172.20.16.0/24 is directly connected, 1d21h, ATM4/0.1

L    172.20.16.1/32 is directly connected, 1d21h, ATM4/0.1

C    10.6.100.0/24 is directly connected, 1d21h, Loopback1

L    10.6.200.21/32 is directly connected, 1d21h, Loopback0

S    192.168.40.0/24 [1/0] via 172.20.16.6, 1d21h

Output of show route backup Command: Example

The following is sample output from the show route backup command: 

RP/0/RP0/CPU0:router# show route backup

Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP

       O - OSPF, IA - OSPF inter area, N1 - OSPF NSSA external type 1

       N2 - OSPF NSSA external type 2, E1 - OSPF external type 1

       E2 - OSPF external type 2, E - EGP, i - ISIS, L1 - IS-IS level-1

       L2 - IS-IS level-2, ia - IS-IS inter area

       su - IS-IS summary null, * - candidate default

       U - per-user static route, o - ODR, L - local

S    172.73.51.0/24 is directly connected, 2d20h, GigabitEthernet2/2

                 Backup  O E2 [110/1] via 10.12.12.2, POS3/0

Output of show route best-local Command: Example

The following is sample output from the show route best-local command: 

RP/0/RP0/CPU0:router# show route best-local 10.12.12.1

Routing entry for 10.12.12.1/32

  Known via "local", distance 0, metric 0 (connected)

  Routing Descriptor Blocks

    10.12.12.1 directly connected, via POS3/0

      Route metric is 0

Output of show route connected Command: Example

The following is sample output from the show route connected command: 

RP/0/RP0/CPU0:router# show route connected

Gateway of last resort is 172.23.54.1 to network 0.0.0.0

C    10.2.210.0/24 is directly connected, 1d21h, Ethernet0

C    172.20.16.0/24 is directly connected, 1d21h, ATM4/0.1

C    10.6.100.0/24 is directly connected, 1d21h, Loopback1

Output of show route local Command: Example

The following is sample output from the show route local command: 

RP/0/RP0/CPU0:router# show route local

L    10.10.10.1/32 is directly connected, 00:14:36, Loopback0

L    10.91.36.98/32 is directly connected, 00:14:32, Ethernet0/0

L    172.22.12.1/32 is directly connected, 00:13:35, POS3/0

L    192.168.20.2/32 is directly connected, 00:13:27, GigabitEthernet2/0

L    10.254.254.1/32 is directly connected, 00:13:26, GigabitEthernet2/2

Output of show route longer-prefixes Command: Example

The following is sample output from the show route longer-prefixes command: 

RP/0/RP0/CPU0:router# show route ipv4 172.16.0.0/8 longer-prefixes

Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP

       O - OSPF, IA - OSPF inter area, N1 - OSPF NSSA external type 1

       N2 - OSPF NSSA external type 2, E1 - OSPF external type 1

       E2 - OSPF external type 2, E - EGP, i - ISIS, L1 - IS-IS level-1

       L2 - IS-IS level-2, ia - IS-IS inter area

       su - IS-IS summary null, * - candidate default

       U - per-user static route, o - ODR, L - local

Gateway of last resort is 172.23.54.1 to network 0.0.0.0

S    172.16.2.0/32 is directly connected, 00:00:24, Loopback0

S    172.16.3.0/32 is directly connected, 00:00:24, Loopback0

S    172.16.4.0/32 is directly connected, 00:00:24, Loopback0

S    172.16.5.0/32 is directly connected, 00:00:24, Loopback0

S    172.16.6.0/32 is directly connected, 00:00:24, Loopback0

S    172.16.7.0/32 is directly connected, 00:00:24, Loopback0

S    172.16.8.0/32 is directly connected, 00:00:24, Loopback0

S    172.16.9.0/32 is directly connected, 00:00:24, Loopback0

Output of show route next-hop Command: Example

The following is sample output from the show route next-hop command: 

RP/0/RP0/CPU0:router# show route next-hop 10.0.0.1

Routing entry for 10.0.0.0/24

  Known via "connected", distance 0, metric 0 (connected)

  Routing Descriptor Blocks

    10.0.0.50 directly connected, via GigabitEthernet6/0

      Route metric is 0

Where to Go Next

For additional information on the protocols that interact with RIB, you may want to see the following publications:

•Implementing BGP on Cisco IOS XR Software

•Implementing IS-IS on Cisco IOS XR Software

•Implementing OSPF on Cisco IOS XR Software

•RIB Commands on Cisco IOS XR Software

Additional References

The following sections provide references related to implementing RIB on Cisco IOS XR software:

Related Documents

Related Topic
Document Title

Routing Information Base commands: complete command syntax, command modes, command history, defaults, usage guidelines, and examples

RIB Commands on Cisco IOS XR Software in the Cisco IOS XR Routing Command Reference, Release 3.2

BGP commands: complete command syntax, command modes, command history, defaults, usage guidelines, and examples

BGP Commands on Cisco IOS XR Software, in the Cisco IOS XR Routing Command Reference, Release 3.2

IS-IS commands: complete command syntax, command modes, command history, defaults, usage guidelines, and examples

IS-IS Commands on Cisco IOS XR Software in the Cisco IOS XR Routing Command Reference, Release 3.2

OSPF commands: complete command syntax, command modes, command history, defaults, usage guidelines, and examples

OSPF Commands on Cisco IOS XR Software in the Cisco IOS XR Routing Command Reference, Release 3.2

OSPFv3 commands: complete command syntax, command modes, command history, defaults, usage guidelines, and examples

OSPFv3 Commands on Cisco IOS XR Software in the Cisco IOS XR Routing Command Reference, Release 3.2

Multicast commands: complete command syntax, command modes, command history, defaults, usage guidelines, and examples

Cisco IOS XR Multicast Command Reference, Release 3.2

Multicast configuration: complete command syntax, command modes, command history, defaults, usage guidelines, and examples

Cisco IOS XR Multicast Configuration Guide, Release 3.2


Standards

Standards
Title

No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature.

—


MIBs

MIBs
MIBs Link

•IP-FORWARD-MIB

•RFC1213-MIB

To locate and download MIBs for selected platforms using Cisco IOS XR software, use the Cisco MIB Locator found at the following URL:

http://cisco.com/public/sw-center/netmgmt/cmtk/mibs.shtml


RFCs

RFCs
Title

No new or modified RFCs are supported by this feature, and support for existing RFCs has not been modified by this feature.

—


Technical Assistance

Description
Link

The Cisco Technical Support website contains thousands of pages of searchable technical content, including links to products, technologies, solutions, technical tips, and tools. Registered Cisco.com users can log in from this page to access even more content.

http://www.cisco.com/techsupport