05-Network Connectivity

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21-IP forwarding basics configuration
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21-IP forwarding basics configuration 65.25 KB

Contents

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

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

Enabling IPv4 packet forwarding on an interface with no IPv4 address configured······························ 1

Enabling IPv6 packet forwarding on an interface with no IPv6 address configured······························ 2

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

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

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

Configuring load sharing mode········································································································ 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 Network Connectivity 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: 4

 

Flag:

  U:Useable   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 IPv4 packet forwarding on an interface with no IPv4 address configured

About this task

On a device that supports both IPv4 and IPv6, the next hop of an IPv4 packet might be an IPv4 address or an IPv6 address. If the output interface has no IPv4 address configured, the interface cannot forward the IPv4 packet. To solve this problem, enable this feature on the interface. This feature allows the interface to forward IPv4 packets even though the interface has no IPv4 address configured.

Restrictions and guidelines

You can configure this feature in any view in which an IPv4 address can be configured.

Procedure

1.     Enter system view.

system-view

2.     Enter interface view.

interface interface-type interface-number

3.     Enable IPv4 packet forwarding on an interface that has no IPv4 address configured.

ip forwarding

By default, IPv4 packet forwarding is disabled on an interface that has no IPv4 address configured.

Enabling IPv6 packet forwarding on an interface with no IPv6 address configured

About this task

On a device that supports both IPv4 and IPv6, the next hop of an IPv4 packet might be an IPv4 address or an IPv6 address. If the output interface has no IPv6 address configured, the interface cannot forward the IPv6 packet. To solve this problem, enable this feature on the interface. This feature allows the interface to forward IPv6 packets even though the interface has no IPv6 address configured.

Restrictions and guidelines

You can configure this feature in any view in which an IPv6 address can be configured.

Procedure

4.     Enter system view.

system-view

5.     Enter interface view.

interface interface-type interface-number

6.     Enable IPv6 packet forwarding on an interface that has no IPv6 address configured.

ipv6 forwarding

By default, IPv6 packet forwarding is disabled on an interface that has no IPv4 address configured.

Display and maintenance commands for FIB table

Execute display commands in any view.

 

Task

Command

Display FIB entries.

display fib  [ 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.

Configuring load sharing mode

About this task

In the per-flow load sharing mode, the device forwards flows over equal-cost routes. Packets of one flow travel along the same routes. You can configure the device to identify a flow based on the following criteria: source IP address, destination IP address, source port number, destination port number, and IP protocol number.

In the per-packet load sharing mode, the device forwards packets over equal-cost routes.

Restrictions and guidelines

Per-packet load sharing does not take effect on packets that are fast forwarded. It takes effect only on those packets that are delivered to the CPU. For more information about configuring load balancing for fast forwarding, see fast forwarding configuration in Network Connectivity Configuration Guide.

Procedure

7.     Enter system view.

system-view

8.     Configure load sharing.

ip load-sharing mode { per-flow [ dest-ip | dest-port | ip-pro | src-ip | src-port ] * | per-packet } global

By default, the device performs per-flow load sharing.

 

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