Cisco IOS XR Routing Configuration Guide, Release 3.0
Implementing and Monitoring 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

Comparison of Cisco IOS RIB and Cisco Cisco IOS XR 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

show route: Example

show route backup: Example

show route best-local: Example

show route connected: Example

show route local: Example

show route longer-prefixes: Example

show route next-hop: Example

Where to Go Next

Additional References

Related Documents

Standards

MIBs

RFCs


Implementing and Monitoring RIB on Cisco IOS XR Software

The Routing Information Base (RIB) is a distributed collection of information about a network's routing connectivity between all of its nodes.

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

Feature Specifications for Implementing and Monitoring RIB on Cisco IOS XR

Feature History
 
Release
Modification

Release 2.0

This feature was introduced.


Software

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

•You must be a member of a user group associated with the proper task IDs for routing commands. Task IDs for commands are listed in the Cisco IOS XR Task ID Reference 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

•Comparison of Cisco IOS RIB and Cisco Cisco IOS XR 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 the RIB. The RIB stores these routes and selects the best ones from among all the routing protocols. Those routes are downloaded to the line cards for use in forwarding packets. The acronym RIB is used both to refer to the RIB processes, and to the collection of route data contained within the RIB.

Within a protocol, routes are selected based on the metrics in use by that protocol. A protocol will download its best routes (lowest or tied metric) to the RIB. The RIB will select the best overall route by comparing the administrative distance of the associated protocol.

Comparison of Cisco IOS RIB and Cisco Cisco IOS XR RIB

The key differences in the function of the RIB feature in Cisco IOS software and Cisco IOS XR software are:

•RIB is its own process on the Cisco IOS XR system.

•RIB can be placed on any desired Route Processor (RP) node on the network running any routing protocol.

RIB Data Structures in BGP and Other Protocols

RIB is not used in Border Gateway Protocol (BGP) or other protocols, such as Protocol Independent Multicast (PIM) or Multicast Source Discovery Protocol (MSDP). However, these protocols use 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). The 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 the RP to forward packets is called the Forwarding Information Base (FIB). The RIB processes do not build the FIBs. Instead, the RIB downloads the set of selected best routes to the FIB processes, by means of the Bulk Content Downloader (BCDL) process, onto each line card. The FIBs are then constructed.

RIB Administrative Distance

Forwarding is done based on the longest match. If you are forwarding a packet destined to 10.0.2.1, you will prefer 10.0.2.0/24 over 10.0.0.0/16 because a /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 downloaded 10.0.1.0/24 to the RIB, the 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 4.

Table 4 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. Please refer to 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, the 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). Please refer to the multicast documentation for more information on using and configuring multicast.

The 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, the RIB processes can be placed on any available node. In the Release 2.0 of Cisco IOS XR software, multiple RPs are not supported.

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 [ipv4 | ipv6] [unicast | multicast] summary

2. show route [list list-name] [protocol [process-id]] [ipv4 | ipv6] [unicast | multicast] [ip-address [mask]]

DETAILED STEPS

 
Command or Action
Purpose

Step 1 

show route [ipv4 | ipv6] [unicast | multicast] summary

Example:

RP/0/RP1/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 [list list-name] [protocol [process-id]] [ipv4 | ipv6] [unicast | multicast] [ip-address [mask]]

Example:

RP/0/RP1/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 will display 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 [list list-name] [protocol [instance]] [ipv4 | ipv6] [unicast | multicast] [ip-address [mask]]

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

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

4. show route [ipv4 | ipv6] [unicast | multicast] connected

5. show route [ipv4 | ipv6] [unicast | multicast] local [interface]

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

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

DETAILED STEPS

 
Command or Action
Purpose

Step 1 

show route [list list-name] [protocol [instance]] [ipv4 | ipv6] [unicast | multicast] [ip-address [mask]]

Example:

RP/0/RP1/CPU0:router# show route list list1 bgp aspo ipv4 unicast 192.168.111/8

Displays the current routes in the RIB.

Step 2 

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

Example:

RP/0/RP1/CPU0:router# show route ipv4 unicast backup 192.168.111/8

Displays backup routes in the RIB.

Step 3 

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

Example:

RP/0/RP1/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 [ipv4 | ipv6] [unicast | multicast] connected

Example:

RP/0/RP1/CPU0:router# show route ipv4 unicast connected

Displays the current connected routes of the routing table.

Step 5 

show route [ipv4 | ipv6] [unicast | multicast] local [interface]

Example:

RP/0/RP1/CPU0:router# show route ipv4 unicast local

Displays local routes receiving routing updates from the RIB.

Step 6 

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

Example:

RP/0/RP1/CPU0:router# show route ipv4 unicast 192.168.111/8 longer-prefixes

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

Step 7 

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

Example:

RP/0/RP1/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. The RIB computes connectivity of the router with other nodes in the network based on input from the routing protocols. It may be used to monitor and troubleshoot the connections between the RIB and its clients. 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 examples are provided:

•show route: Example

•show route backup: Example

•show route best-local: Example

•show route connected: Example

•show route local: Example

•show route longer-prefixes: Example

•show route next-hop: Example

show route: Example

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

RP/0/RP1/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

show route backup: Example

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

RP/0/RP1/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

show route best-local: Example

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

RP/0/RP1/CPU0:router# show route best-local 192.168.243.11 

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

show route connected: Example

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

RP/0/RP1/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

show route local: Example

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

RP/0/RP1/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

show route longer-prefixes: Example

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

RP/0/RP1/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

show route next-hop: Example

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

RP/0/RP1/CPU0:router# show route next-hop 192.168.1.34

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 consult 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

•Implementing OSPFv3 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

RIB Commands on Cisco IOS XR Software

BGP commands

BGP Commands on Cisco IOS XR Software

IS-IS commands

IS-IS Commands on Cisco IOS XR Software

OSPF commands

OSPF Commands on Cisco IOS XR Software

OSPFv3 commands

OSPFv3 Commands on Cisco IOS XR Software

Cisco CRS-1 Series Carrier Routing System router interface software

Cisco CRS-1 Series Carrier Routing System Router Interface Configuration Guide

Multicast commands

Multicast Commands on Cisco IOS XR Software

Multicast configuration

Cisco IOS XR Multicast Configuration Guide

Cisco CRS-1 Series Carrier Routing System Craft Web Interface (CWI)

Cisco CRS-1 Series Carrier Routing System Craft Works Interface (CWI) Configuration


Standards

Standards
Title

No new or modified standards are supported by the features in this document, and support for existing standards had not been modified by the features in this document.

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MIBs

MIBs
MIBs Link

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

To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL:

http://www.cisco.com/go/mibs


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.

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