04-Layer 3-IP Services Configuration Guide

HomeSupportResource CenterH3C S5560S-EI&S5560S-SI&S5500V3-SI Switch Series Configuration Guides-R612x-6W10204-Layer 3-IP Services Configuration Guide
05-IP forwarding basics configuration
Title Size Download
05-IP forwarding basics configuration 46.81 KB

Contents

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

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

Saving the IP forwarding entries to a file······································································································· 1

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

Configuring load sharing··············································································· 3

About load sharing············································································································································· 3

Enabling local-first load sharing······················································································································ 3


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

 

Destination count: 4 FIB entry count: 4

 

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.

Saving the IP forwarding entries to a file

Restrictions and guidelines

The feature automatically creates the file if you specify a nonexistent file. If the file already exists, this feature overwrites the file content.

This feature triggers one-time saving of the IP forwarding entries.

To automatically save the IP forwarding entries periodically, configure a schedule for the device to automatically run the ip forwarding-table save command. For information about scheduling a task, see Fundamentals Configuration Guide.

Procedure

To save the IP forwarding entries to a file, execute the following command in any view:

ip forwarding-table save filename filename

Display and maintenance commands for FIB table

Execute display commands in any view.

 

Task

Command

Display FIB entries.

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

 


Configuring load sharing

About load sharing

If a routing protocol finds multiple equal-cost best routes to the same destination, the device forwards packets over the equal-cost routes to implement load sharing.

Enabling local-first load sharing

About local-first load sharing

Local-first load sharing distributes traffic preferentially across the output interfaces on the receiving IRF member device if output interfaces for multiple equal-cost routes are on different members. This feature enhances packets forwarding efficiency.

Procedure

1.        Enter system view.

system-view

2.        Enable local-first load sharing.

ip load-sharing local-first enable

By default, local-first load sharing is enabled.