Contents

Configuring IP forwarding basic settings························································ 1

About FIB table······························································································································· 1

Enabling SNMP notifications for FIB events······················································································ 1

Display and maintenance commands for IP forwarding basics··························································· 2

Display and maintenance commands for FIB table····································································· 2

Displaying the difference information of FIB entries between the specified cards························· 2

Configuring IP forwarding basic settings

About FIB table

A device uses the FIB table to make packet forwarding decisions.

A device selects optimal routes from the routing table, and puts them into the FIB table. Each FIB entry specifies the next hop IP address and output interface for packets destined for a specific subnet or host.

For more information about the routing table, see Layer 3—IP Routing Configuration Guide.

Use the display fib command to display the FIB table. The following example displays the entire FIB table.

<Sysname> display fib

Route destination count: 4

Directly-connected host count: 0

Flag:

  U:Usable   G:Gateway   H:Host   B:Blackhole   D:Dynamic   S:Static

  R:Relay     F:FRR

Destination/Mask   Nexthop         Flag     OutInterface/Token       Label

10.2.0.0/16        10.2.1.1        U        GE1/0/1                  Null

10.2.1.1/32        127.0.0.1       UH       InLoop0                  Null

127.0.0.0/8        127.0.0.1       U        InLoop0                  Null

127.0.0.1/32       127.0.0.1       UH       InLoop0                  Null

A FIB entry includes the following items:

·     Destination—Destination IP address.

·     Mask—Network mask. The mask and the destination address identify the destination network. A logical AND operation between the destination address and the network mask yields the address of the destination network. For example, if the destination address is 192.168.1.40 and the mask 255.255.255.0, the address of the destination network is 192.168.1.0. A network mask includes a certain number of consecutive 1s. It can be expressed in dotted decimal format or by the number of the 1s.

·     Nexthop—IP address of the next hop.

·     Flag—Route flag.

·     OutInterface—Output interface.

·     Token—MPLS Label Switched Path index number.

·     Label—Inner label.

Enabling SNMP notifications for FIB events

About this task

This feature enables the FIB module to generate SNMP notifications for critical FIB events, such as exceeding of the message queue length threshold. The SNMP notifications are sent to the SNMP module.

For the SNMP notifications to be sent correctly, you must also configure SNMP. For more information about SNMP configuration, see Network Management and Monitoring Configuration Guide.

Procedure

1.     Enter system view.

system-view

2.     Enable SNMP notifications for FIB events.

snmp-agent trap enable fib

By default, SNMP notifications for FIB events are enabled.

Display and maintenance commands for IP forwarding basics

Display and maintenance commands for FIB table

·     To display FIB entries, execute the following command in any view:

display fib  [ vpn-instance vpn-instance-name ] [ ip-address [ mask | mask-length ] ] [ slot slot-number  ]

Displaying the difference information of FIB entries between the specified cards

·     To display the difference information of FIB entries between the specified cards, execute the following command in any view:

display fib prefix diff [ all | [ vpn-instance vpn-instance-name ] [ ip-address [ mask | mask-length ] ] ] slot slot-number1 slot slot-number2

·     To display the difference information of FIB VN entries between the specified cards, execute the following command in any view:

display fib vn diff [ id id ] slot slot-number1 slot slot-number2