Cisco Nexus 7000 Series NX-OS Unicast Routing Configuration Guide, Release 4.0
Managing the Unicast RIB and FIB
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Table Of Contents

Managing the Unicast RIB and FIB

Information About the Unicast RIB and FIB

Layer 3 Consistency Checker

Virtualization Support

Licensing Requirements for the Unicast RIB and FIB

Guidelines and Limitations

Managing the Unicast RIB and FIB

Displaying Module FIB Information

Configuring Load Sharing in the Unicast RIB

Displaying Routing and Adjacency Information

Triggering the Layer 3 Consistency Checker

Clearing Forwarding Information in the FIB

Clearing Routes in the Unicast RIB

Verifying the Unicast RIB and FIB

Additional References

Related Documents

Feature History for Unicast RIB and FIB


Managing the Unicast RIB and FIB

This chapter describes how to manage routes in the unicast Routing Information Base (RIB) and the Forwarding Information Base (FIB) on the Cisco NX-OS device.

This chapter includes the following sections:

•Information About the Unicast RIB and FIB

•Licensing Requirements for the Unicast RIB and FIB

•Guidelines and Limitations

•Managing the Unicast RIB and FIB

•Verifying the Unicast RIB and FIB

•Additional References

•Feature History for Unicast RIB and FIB

Information About the Unicast RIB and FIB

The unicast RIB (IPv4 RIB and IPv6 RIB) and FIB are part of the Cisco NX-OS forwarding architecture, as shown in Figure 14-1.

Figure 14-1 Cisco NX-OS Forwarding Architecture

The unicast RIB exists on the active supervisor. It maintains the routing table with directly connected routes, static routes, and routes learned from dynamic unicast routing protocols. The unicast RIB also collects adjacency information from sources such as the Address Resolution Protocol (ARP). The unicast RIB determines the best next hop for a given route and populates the unicast forwarding information bases (FIB) on the modules by using the services of the unicast FIB distribution module (FDM).

Each dynamic routing protocol must update the unicast RIB for any route that has timed out. The unicast RIB then deletes that route and recalculates the best next hop for that route (if an alternate path is available).

This section includes the following topics:

•Layer 3 Consistency Checker

•Virtualization Support

Layer 3 Consistency Checker

In rare instances, an inconsistency can occur between the unicast RIB and the FIB on each module. In Cisco NX-OS Release 4.0(3) and later releases, Cisco NX-OS supports the Layer 3 consistency checker. This feature detects inconsistencies between the unicast IPv4 RIB on the supervisor module and the FIB on each interface module. Inconsistencies include the following:

•Missing prefix

•Extra prefix

•Wrong next-hop address

•Incorrect Layer 2 rewrite string in the ARP or neighbor discovery (ND) cache.

The Layer 3 consistency checker compares the FIB entries to the latest adjacency information from the Adjacency Manager (AM) and logs any inconsistencies. The consistency checker then compares the unicast RIB prefixes to the module FIB and logs any inconsistencies. See the "Triggering the Layer 3 Consistency Checker" section.

You can then manually clear any inconsistencies. See the "Clearing Forwarding Information in the FIB" section.

Virtualization Support

The Unicast RIB and FIB support Virtual Routing and Forwarding instances (VRFs). VRFs exist within virtual device contexts (VDCs). By default, Cisco NX-OS places you in the default VDC and default VRF unless you specifically configure another VDC and VRF. For more information, see the Cisco NX-OS Virtual Device Context Configuration Guide. and see Chapter 13, "Configuring Layer 3 Virtualization."

Licensing Requirements for the Unicast RIB and FIB

The following table shows the licensing requirements for this feature:

Product
License Requirement

NX-OS

The unicast RIB and FIB require no license. Any feature not included in a license package is bundled with the Cisco NX-OS system images and is provided at no extra charge to you. For a complete explanation of the NX-OS licensing scheme, see the Cisco NX-OS Licensing Guide, Release 4.0.


Guidelines and Limitations

Unicast RIB and FIB have the following guidelines and limitations and restrictions:

•The FIB TCAM is 128,000 physical entries, which is divided into the following sections by default:

–56,000 IPv4 unicast routes (56,000 physical entries)

–32,000 IPv4 multicast routes or IPv6 unicast routes (64,000 physical entries)

–2000 IPv6 multicast routes (8000 physical entries)

•You cannot change the default FIB division.

Managing the Unicast RIB and FIB

This section includes the following topics:

•Displaying Module FIB Information

•Configuring Load Sharing in the Unicast RIB

•Displaying Routing and Adjacency Information

•Triggering the Layer 3 Consistency Checker

•Clearing Forwarding Information in the FIB

•Clearing Routes in the Unicast RIB

Note If you are familiar with the Cisco IOS CLI, be aware that the Cisco NX-OS commands for this feature might differ from the Cisco IOS commands that you would use.

Displaying Module FIB Information

You can display the FIB information on a module.

DETAILED STEPS

To display the FIB information on a module, use the following commands in any mode:

Command
Purpose 
show ip fib adjacency module slot


Example:

switch# show ip fib adjacency module 
2

Displays the adjacency information for IPv4. 

show forwarding {ipv4 | ipv6} 
adjacency module slot


Example:

switch# show forwarding ipv6 
adjacency module 2

Displays the adjacency information for IPv4 or IPv6. 

show ip fib interfaces module slot


Example:

switch# show ip fib interfaces module 
2

Displays the FIB interface information for IPv4. 

show ip fib route module slot


Example:

switch# show ip fib route module 2

Displays the route table for IPv4. 

show forwarding {ipv4 | ipv6} route 
module slot


Example:

switch# show forwarding ipv6 route 
module 2

Displays the route table for IPv4 or IPv6.


This example shows the FIB contents on a module: 

switch# show ip fib route module 2


IPv4 routes for table default/base


------------------+------------------+---------------------

Prefix            | Next-hop         | Interface

------------------+------------------+---------------------

0.0.0.0/32          Drop               Null0

255.255.255.255/32  Receive            sup-eth1

Configuring Load Sharing in the Unicast RIB

Dynamic routing protocols, such as Open Shortest Path First (OSPF), support load balancing with equal-cost multipath (ECMP). The routing protocol determines its best routes based on the metrics configured for the protocol and installs up to the protocol-configured maximum paths in the unicast RIB. The unicast RIB compares the administrative distances of all routing protocol paths in the RIB and selects a best path set from all of the path sets installed by the routing protocols. The unicast RIB installs this best path set into the FIB for use by the forwarding plane.

The forwarding plane uses a load-sharing algorithm to select one of the installed paths in the FIB to use for a given data packet.

You can configure the following load-sharing settings:

•load-share mode—Selects the best path based on the destination address and port, or the source and the destination address and port.

•Hash seed—Sets the random seed for the hash algorithm.

To configure the unicast RIB load-sharing algorithm, use the following command in global configuration mode:

Command
Purpose 
ip load-sharing address {destination 
port destination | source-destination 
[port source-destination]} 
[universal-id seed]


Example:

switch(config)# ip load-sharing 
address source-destination

Configures the unicast RIB load-sharing algorithm for data traffic. The hash seed range is from 1 to 4294967295.


To display the unicast RIB load-sharing algorithm, use the following command in any mode:

Command
Purpose 
show ip load-sharing 


Example:

switch(config)# show ip load-sharing 
address source-destination

Configures the unicast RIB load-sharing algorithm for data traffic. The hash seed range is from 1 to 4294967295.


To display the route that the unicast RIB uses for a particular source address and destination address, use the following command in any mode:

Command
Purpose 
show routing hash source-addr 
dest-addr [source-port dest-port] 
[vrf vrf-name]


Example:

switch# show routing hash 192.0.2.1 
10.0.0.1

Configures the unicast RIB load-sharing algorithm for data traffic. The source address and destination address format is x.x.x.x. The source port and destination port range is from 1 to 65535. The VRF name can be any case-sensitive alphanumeric string up to 64 characters.


This example shows the route selected for a source/destination pair: 

switch# show routing hash 10.0.0.5 30.0.0.2

  Load-share parameters used for software forwarding:

  load-share mode: address source-destination port source-destination

  Universal-id seed: 0xe05e2e85

  Hash for VRF "default"

  Hashing to path *20.0.0.2 (hash: 0x0e), for route:

Displaying Routing and Adjacency Information

You can display the routing and adjacency information.

To display the routing and adjacency information, use the following commands in any mode:

Command
Purpose 
show {ip | ipv6} route [route-type | 
interface int-type number | next-hop]


Example:

switch# show ip route

Displays the unicast route table. The route-type argument can be a single route prefix, direct, static, or a dynamic route protocol. Use the ? command to see the supported interfaces. 

show {ip | ipv6} adjacency [prefix | 
interface-type number [summary]| 
non-best] [detail] [vrf vrf-id]


Example:

switch# show ip adjacency

Displays the adjacency table. The argument ranges are as follows:

•prefix—Any IPv4 or IPv6 prefix address.

•interface-type number—Use the ? command to see the supported interfaces.

•vrf-id—Any case-sensitive alphanumeric string up to 64 characters. 

show {ip | ipv6} routing [route-type 
| interface int-type number | 
next-hop | recursive-next-hop | 
summary | updated {since | until} 
time]


Example:

switch# show routing summary

Displays the unicast route table. The route-type argument can be a single route prefix, direct, static, or a dynamic route protocol. Use the ? command to see the supported interfaces.


This example displays the unicast route table: 

switch# show ip route

IP Route Table for Context "default"

'*' denotes best ucast next-hop       '**' denotes best mcast next-hop

'[x/y]' denotes [preference/metric]


0.0.0.0/0, 1 ucast next-hops, 0 mcast next-hops

   *via 10.1.1.1, mgmt0, [1/0], 5d21h, static

0.0.0.0/32, 1 ucast next-hops, 0 mcast next-hops

   *via Null0, [220/0], 1w6d, local, discard

10.1.0.0/22, 1 ucast next-hops, 0 mcast next-hops, attached

   *via 10.1.1.55, mgmt0, [0/0], 5d21h, direct

10.1.0.0/32, 1 ucast next-hops, 0 mcast next-hops, attached

   *via 10.1.0.0, Null0, [0/0], 5d21h, local

10.1.1.1/32, 1 ucast next-hops, 0 mcast next-hops, attached

   *via 10.1.1.1, mgmt0, [2/0], 5d16h, am

10.1.1.55/32, 1 ucast next-hops, 0 mcast next-hops, attached

   *via 10.1.1.55, mgmt0, [0/0], 5d21h, local

10.1.1.253/32, 1 ucast next-hops, 0 mcast next-hops, attached

   *via 10.1.1.253, mgmt0, [2/0], 5d20h, am

10.1.3.255/32, 1 ucast next-hops, 0 mcast next-hops, attached

   *via 10.1.3.255, mgmt0, [0/0], 5d21h, local

255.255.255.255/32, 1 ucast next-hops, 0 mcast next-hops

   *via Eth Inband Port, [0/0], 1w6d, local

This example shows the adjacency information: 

switch# show ip adjacency


IP Adjacency Table for context default

Total number of entries: 2

Address         Age       MAC Address     Pref Source     Interface       Best

10.1.1.1        02:20:54  00e0.b06a.71eb  50   arp        mgmt0           Yes

10.1.1.253      00:06:27  0014.5e0b.81d1  50   arp        mgmt0           Yes

switch

Triggering the Layer 3 Consistency Checker

You can manually trigger the Layer 3 consistency checker.

To manually trigger the Layer 3 consistency checker, use the following commands in global configuration mode:

Command
Purpose 
test forwarding inconsistency [ip | 
ipv4] [unicast] [vrf vrf-name] 
[module {slot| all}] 


Example:

switch(config)# test forwarding 
inconsistency

Starts a Layer 3 consistency check. The vrf-name can be any case-sensitive alphanumeric string up to 64 characters. The slot range is from 1 to 10.


To stop the Layer 3 consistency checker, use the following commands in global configuration mode:

Command
Purpose 
test forwarding inconsistency [ip | 
ipv4] [unicast] [vrf vrf-name] 
[module {slot| all}] stop


Example:

switch(config)# test forwarding 
inconsistency stop

Stops a Layer 3 consistency check. The vrf-name can be any case-sensitive alphanumeric string up to 64 characters. The slot range is from 1 to 10.


To display the Layer 3 inconsistencies, use the following commands in any mode:

Command
Purpose 
show forwarding inconsistency [ip | 
ipv4] [unicast] [vrf vrf-name] 
[module {slot| all}] 


Example:

switch(config)# show forwarding 
inconsistency

Displays the results of a Layer 3 consistency check. The vrf-name can be any case-sensitive alphanumeric string up to 64 characters. The slot range is from 1 to 10.


Clearing Forwarding Information in the FIB

You can clear one or more entries in the FIB. Clearing a FIB entry does not affect the unicast RIB.

Caution The clear forwarding command disrupts forwarding on the device.

To clear an entry in the FIB, including a Layer 3 inconsistency, use the following command in any mode:

Command
Purpose 
clear forwarding {ip | ipv4 | ipv6} 
route {* | prefix} [vrf vrf-name] 
[module {slot| all}] 


Example:

switch(config)# clear forwarding ip 
route *

Clears one or more entries from the FIB. The route options are as follows:

•*—All routes.

•prefix—Any IP or IPv6 prefix.

The vrf-name can be any case-sensitive alphanumeric string up to 64 characters. The slot range is from 1 to 10.


Clearing Routes in the Unicast RIB

You can clear one or more routes from the unicast RIB.

Caution The * keyword is severely disruptive to routing.

To clear one or more entries in the unicast RIB, use the following commands in any mode:

Command
Purpose 
clear {ip | ipv4 | ipv6} route {* | 
{route | prefix/length}[next-hop 
interface]} [vrf vrf-name] 


Example:

switch(config)# clear ip route 
10.2.2.2

Clears one or more routes from both the unicast RIB and the all the module FIBs. The route options are as follows:

•*—All routes.

•route—An individual IP or IPv6 route.

•prefix/length—Any IP or IPv6 prefix.

•next-hop—The next-hop address

•interface—The interface to reach the next-hop address.

The vrf-name can be any case-sensitive alphanumeric string up to 64 characters. 

clear routing [multicast | unicast] 
[ip | ipv4 | ipv6] {* | {route | 
prefix/length}[next-hop interface]} 
[vrf vrf-name] 


Example:

switch(config)# clear routing ip 
10.2.2.2

Clears one or more routes from the unicast RIB. The route options are as follows:

•*—All routes.

•route—An individual IP or IPv6 route.

•prefix/length—Any IP or IPv6 prefix.

•next-hop—The next-hop address

•interface—The interface to reach the next-hop address.

The vrf-name can be any case-sensitive alphanumeric string up to 64 characters.


Verifying the Unicast RIB and FIB

To verify the unicast RIB and FIB information, use the following commands:

Command
Purpose

show forwarding adjacency

Displays the adjacency table on a module.

show forwarding distribution {clients | fib-state}

Displays the FIB distribution information.

show forwarding interfaces module slot

Displays the FIB information for a module.

show forwarding {ip | ipv4 | ipv6} route

Displays routes in the FIB.

show {ip | ipv6} adjacency

Displays the adjacency table.

show {ip | ipv6} route

Displays IPv4 or IPv6 routes from the unicast RIB.

show routing

Displays routes from the unicast RIB.


Additional References

For additional information related to managing unicast RIB and FIB, see the following sections:

•Related Documents

•Feature History for Unicast RIB and FIB

Related Documents

Related Topic
Document Title

unicast RIB and FIB CLI commands

Cisco NX-OS Unicast Routing Command Reference, Release 4.0


Feature History for Unicast RIB and FIB

Table 14-1 lists the release history for this feature.

Table 14-1 Feature History for Unicast RIB and FIB

Feature Name
Releases
Feature Information

Unicast RIB and FIB

4.0(3)

Added support to clear individual routes in unicast RIB and FIB.

Unicast RIB and FIB

4.0(1)

This feature was introduced.