Cisco IOS XR Routing Configuration Guide for the Cisco CRS-1 Router, Release 3.9
Implementing and Monitoring RIB
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Implementing and Monitoring RIB

Contents

Implementing and Monitoring RIB

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 how to implement and monitor RIB on 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 Additional References section 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 Commands Master List for the Cisco CRS Router.


Feature History for Implementing and Monitoring RIB

Release

Modification

Release 2.0

This feature was introduced.

Release 3.0

No modification.

Release 3.2 No modification.

Release 3.3.0

VPN routing and forwarding (VRF) support was added to the command syntax.

Release 3.4.0

RIB statistics support was added using the show rib statistics command. Disabling RIB next-hop dampening was supported.

Release 3.5.0

The following features were supported:

  • IP fast reroute loop-free alternates computation
  • IPv6 Provider Edge and IPv6 VPN Provider Edge over Multiprotocol Label Switching
  • RIB quarantining

Release 3.6.0

No modification.

Release 3.7.0

No modification.

Release 3.8.0

No modification.

Release 3.9.0

No modification.

Prerequisites for Implementing RIB

  • You must be in a user group associated with a task group that includes the proper task IDs. The command reference guides include the task IDs required for each command. If you suspect user group assignment is preventing you from using a command, contact your AAA administrator for assistance.
  • 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

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.

This table lists default administrative distances for the common protocols.



Table 1 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 tables for Cisco IOS XR software 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.

RIB Statistics

RIB supports statistics for messages (requests) flowing between the RIB and its clients. Protocol clients send messages to the RIB (for example, route add, route delete, and next-hop register, and so on). RIB also sends messages (for example, redistribute routes, advertisements, next-hop notifications, and so on). These statistics are used to gather information about what messages have been sent and the number of messages that have been sent. These statistics provide counters for the various messages that flow between the RIB server and its clients. The statistics are displayed using the show rib statistics command.

RIB maintains counters for all requests sent from a client including:

  • Route operations
  • Table registrations
  • Next-hop registrations
  • Redistribution registrations
  • Attribute registrations
  • Synchronization completion

RIB also maintains counters for all requests sent by the RIB. The configuration will disable the RIB next-hop dampening feature. As a result, RIB notifies client immediately when a next hop that client registered for is resolved or unresolved.

RIB also maintains the results of the requests.

IPv6 Provider Edge IPv6 and IPv6 VPN Provider Edge Transport over MPLS

IPv6 Provider Edge (6PE) and IPv6 VPN Provider Edge (6VPE) leverages the existing Multiprotocol Label Switching (MPLS) IPv4 core infrastructure for IPv6 transport. 6PE and 6VPE enables IPv6 sites to communicate with each other over an MPLS IPv4 core network using MPLS label switched paths (LSPs).

RIB supports 6PE and 6VPE by providing 6VPE next hops. The next-hop information is stored in an opaque database in RIB, which is populated by protocol clients with data to be sent to the Forwarding Information Base (FIB).

For detailed information about configuring 6PE and 6VPE over MPLS, see Cisco IOS XR MPLS Configuration Guide for the Cisco CRS Router.

IP Fast Reroute

The IP Fast Reroute (IPFRR) loop-free alternate (LFA) computation provides protection against link failure. Locally computed repair paths are used to prevent packet loss caused by loops that occur during network reconvergence after a failure. For information about IPFRR see Implementing IS-IS on Cisco IOS XR Software module in Cisco IOS XR Routing Configuration Guide for the Cisco CRS Router.

RIB Quarantining

RIB quarantining solves the problem in the interaction between routing protocols and the RIB. The problem is a persistent oscillation between the RIB and routing protocols that occurs when a route is continuously inserted and then withdrawn from the RIB, resulting in a spike in CPU use until the problem is resolved. If there is no damping on the oscillation, then both the protocol process and the RIB process have high CPU use, affecting the rest of the system as well as blocking out other protocol and RIB operations. This problem occurs when a particular combination of routes is received and installed in the RIB. This problem typically happens as a result of a network misconfiguration. However, because the misconfiguration is across the network, it is not possible to detect the problem at configuration time on any single router.

The quarantining mechanism detects mutually recursive routes and quarantines the last route that completes the mutual recursion. The quarantined route is periodically evaluated to see if the mutual recursion has gone away. If the recursion still exists, the route remains quarantined. If the recursion has gone away, the route is released from its quarantine.

The following steps are used to quarantine a route:

  1. RIB detects when a particular problematic path is installed.
  2. RIB sends a notification to the protocol that installed the path.
  3. When the protocol receives the quarantine notification about the problem route, it marks the route as being “quarantined.” If it is a BGP route, BGP does not advertise reachability for the route to its neighbors.
  4. Periodically, RIB tests all its quarantined paths to see if they can now safely be installed (moved from quarantined to "Ok to use" state). A notification is sent to the protocol to indicate that the path is now safe to use.

Flex-LSR Label Switch Processor 140

The Label Switch Processor 140 line card is a scaled down version of Cisco CRS 3 line card. The Flex -LSR feature imposes these limits to download of routes and labels:
  • 16K IPv4 and IPv6 unicast (including VRF) routes
  • 8K IPv4 and IPv6 multicast routes
  • 100K labels

How to Deploy and Monitor RIB

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

Verifying RIB Configuration Using the Routing Table

Perform this task to verify 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 [ vrf { vrf-name | all }] [ afi-all | ipv4 | ipv6 ] [ unicast | multicast | safi-all ] summary [ detail ] [ standby ]

    2.    show route [ vrf { vrf-name | all }] [ afi-all | ipv4 | ipv6 ] [ unicast | multicast | safi-all ] [ protocol [ instance ] | ip-address mask ] [ standby ] [ detail ]


DETAILED STEPS
      Command or Action Purpose
    Step 1 show route [ vrf { vrf-name | all }] [ afi-all | ipv4 | ipv6 ] [ unicast | multicast | safi-all ] summary [ detail ] [ standby ]


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

    Displays route summary information about the specified routing table.

    • The default table summarized is the IPv4 unicast routing table.
     
    Step 2 show route [ vrf { vrf-name | all }] [ afi-all | ipv4 | ipv6 ] [ unicast | multicast | safi-all ] [ protocol [ instance ] | ip-address mask ] [ standby ] [ detail ]


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

    Displays more detailed route information about 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

    Perform this task to verify the operation of routes between nodes.

    SUMMARY STEPS

      1.    show route [vrf {vrf-name | all }] [ afi-all | ipv4 | ipv6 ] [ unicast | multicast | safi-all ] [ protocol [ instance ] | ip-address mask ] [ standby ] [ detail ]

      2.    show route [ vrf { vrf-name | all }] [ afi-all | ipv4 | ipv6 ] [ unicast | multicast | safi-all ] backup [ ip-address ] [ standby ]

      3.    show route [ vrf { vrf-name | all }] [ ipv4 | ipv6 ] [ unicast | multicast | safi-all ] best-local ip-address [ standby ]

      4.    show route [ vrf { vrf-name | all }] [ afi-all | ipv4 | ipv6 ] [ unicast | multicast | safi-all ] connected [ standby ]

      5.    show route [ vrf { vrf-name | all }] [ afi-all | ipv4 | ipv6 ] [ unicast | multicast | safi-all ] local [ interface ] [ standby ]

      6.    show route [ vrf { vrf-name | all }] [ ipv4 | ipv6 ] [ unicast | multicast | safi-all ] longer-prefixes { ip-address mask | ip-address / prefix-length } [ standby ]

      7.    show route [ vrf { vrf-name | all }] [ ipv4 | ipv6 ] [ unicast | multicast | safi-all ] next-hop ip-address [ standby ]


    DETAILED STEPS
        Command or Action Purpose
      Step 1 show route [vrf {vrf-name | all }] [ afi-all | ipv4 | ipv6 ] [ unicast | multicast | safi-all ] [ protocol [ instance ] | ip-address mask ] [ standby ] [ detail ]


      Example:
      RP/0/RP0/CPU0:router# show route list list1 bgp aspo ipv4 unicast 192.168.1.11/8
       

      Displays the current routes in RIB.

       
      Step 2 show route [ vrf { vrf-name | all }] [ afi-all | ipv4 | ipv6 ] [ unicast | multicast | safi-all ] backup [ ip-address ] [ standby ]


      Example:
      RP/0/RP0/CPU0:router# show route ipv4 unicast backup 192.168.1.11/8
       

      Displays backup routes in RIB.

       
      Step 3 show route [ vrf { vrf-name | all }] [ ipv4 | ipv6 ] [ unicast | multicast | safi-all ] best-local ip-address [ standby ]


      Example:
      RP/0/RP0/CPU0:router# show route ipv4 unicast best-local 192.168.1.11/8
       

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

       
      Step 4 show route [ vrf { vrf-name | all }] [ afi-all | ipv4 | ipv6 ] [ unicast | multicast | safi-all ] connected [ standby ]


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

      Displays the current connected routes of the routing table.

       
      Step 5 show route [ vrf { vrf-name | all }] [ afi-all | ipv4 | ipv6 ] [ unicast | multicast | safi-all ] local [ interface ] [ standby ]


      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 [ vrf { vrf-name | all }] [ ipv4 | ipv6 ] [ unicast | multicast | safi-all ] longer-prefixes { ip-address mask | ip-address / prefix-length } [ standby ]


      Example:
      RP/0/RP0/CPU0:router# show route ipv4 unicast longer-prefixes 192.168.1.11/8
      
       

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

       
      Step 7 show route [ vrf { vrf-name | all }] [ ipv4 | ipv6 ] [ unicast | multicast | safi-all ] next-hop ip-address [ standby ]


      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.

       

      Disabling RIB Next-hop Dampening

      Perform this task to disable RIB next-hop dampening.

      SUMMARY STEPS

        1.    router rib

        2.    address-family { ipv4 | ipv6 } next-hop dampening disable

        3.    Do one of the following:

        • end
        • commit


      DETAILED STEPS
          Command or Action Purpose
        Step 1 router rib


        Example:
        RP/0/RP0/CPU0:router# route rib
         

        Enters RIB configuration mode.

         
        Step 2 address-family { ipv4 | ipv6 } next-hop dampening disable


        Example:
        RP/0/RP0/CPU0:router(config-rib)# address family ipv4 next-hop dampening disable
        
         

        Disables next-hop dampening for IPv4 address families.

         
        Step 3 Do one of the following:
        • end
        • commit


        Example:
        RP/0/RP0/CPU0:router(config-rib)# end

        or

        RP/0/RP0/CPU0:router(config-rib)# commit
         

        Saves configuration changes.

        • When you issue the end command, the system prompts you to commit changes:
            Uncommitted changes found, commit them before exiting(yes/no/cancel)?[cancel]:
          • Entering yes saves configuration changes to the running configuration file, exits the configuration session, and returns the router to EXEC mode.
          • Entering no exits the configuration session and returns the router to EXEC mode without committing the configuration changes.
          • Entering cancel leaves the router in the current configuration session without exiting or committing the configuration changes.
        • Use the commit command to save the configuration changes to the running configuration file and remain within the configuration session.
         

        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.

        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, R - RIP, M - mobile, B - BGP
                 D - EIGRP, EX - EIGRP external, 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, R - RIP, M - mobile, B - BGP
                 D - EIGRP, EX - EIGRP external, 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, GigabitEthernet 4/0/0/1
                           Backup  O E2 [110/1] via 10.12.12.2, GigabitEthernet 3/0/0/1
          

        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 GigabitEthernet3/0
                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 
          
          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, GigabitEthernet3/0
          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 longer-prefixes 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 resolving-next-hop command:

          RP/0/RP0/CPU0:router# show route resolving-next-hop 10.0.0.1 
           
          Nexthop matches 0.0.0.0/0
            Known via "static", distance 200, metric 0, candidate default path
            Installed Aug 18 00:59:04.448
            Directly connected nexthops
              172.29.52.1, via MgmtEth0/
        RP0
        /CPU0/0
                Route metric is 0
              172.29.52.1, via MgmtEth0/RP1/CPU0/0
                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 MPLS Layer 3 VPNs in Cisco IOS XR MPLS Configuration Guide for the Cisco CRS Router
        • Implementing BGP in Cisco IOS XR Routing Configuration Guide for the Cisco CRS Router
        • Implementing EIGRP in Cisco IOS XR Routing Configuration Guide for the Cisco CRS Router
        • Implementing IS-IS in Cisco IOS XR Routing Configuration Guide for the Cisco CRS Router
        • Implementing OSPF in Cisco IOS XR Routing Configuration Guide for the Cisco CRS Router
        • Implementing RIP in Cisco IOS XR Routing Configuration Guide for the Cisco CRS Router
        • RIB Commands in Cisco IOS XR Routing Command Reference for the Cisco CRS Router

        Additional References

        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 Cisco IOS XR Routing Command Reference for the Cisco CRS Router

        Standards and RFCs

        Standard/RFC Title
        Draft-ietf-rtgwg-ipfrr-framework-06.txt IP Fast Reroute Framework, by M. Shand and S. Bryant
        Draft-ietf-rtgwg-lf-conv-frmwk-00.txt A Framework for Loop-free Convergence, by M. Shand and S. Bryant

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

        MIBs

        MIB MIBs Link

        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

        Technical Assistance

        Description Link

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        To receive security and technical information about your products, you can subscribe to various services, such as the Product Alert Tool (accessed from Field Notices), the Cisco Technical Services Newsletter, and Really Simple Syndication (RSS) Feeds.

        Access to most tools on the Cisco Support website requires a Cisco.com user ID and password.

        http:/​/​www.cisco.com/​support