Contents

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

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

Enabling the VPN peer-based processing························································································· 1

Enabling split horizon forwarding······································································································ 2

Forwarding specific packets received from VXLAN tunnels in hardware·············································· 2

Enabling SNMP notifications for FIB events······················································································ 2

Display and maintenance commands for IP forwarding basics··························································· 3

Display and maintenance commands for FIB table····································································· 3

Displaying the differences in FIB entries between two member devices······································· 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

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 the VPN peer-based processing

About this task

This feature enables the device to use the VPN peer ID of the routing information in the FIB table to process packets.

This feature must be used together with the apply vpn-peer-id command. For more information about this command, see routing policy commands in Layer 3—IP Routing Command Reference.

Procedure

1.     Enter system view.

system-view

2.     Enable the VPN peer-based processing.

ip forwarding apply vpn-peer-id enable

By default, the VPN peer-based processing is disabled.

Enabling split horizon forwarding

About this task

This feature prevents IPv4, IPv6, and MPLS packets from being forwarded out of the physical interface on which they were received, avoiding network loops.

Restrictions and guidelines

Only the S5580X-HI series switches support this feature.

Procedure (system view)

1.     Enter system view.

system-view

2.     Enable split horizon forwarding.

forwarding split-horizon

By default, split horizon forwarding is disabled.

Forwarding specific packets received from VXLAN tunnels in hardware

About this task

By default, the device forwards packets received from VXLAN tunnels to the CPU for processing when acting as a VTEP in a distributed EVPN gateway network. If a large number of packets are received, packet loss might occur because of software rate limit, which might cause service exceptions on downlink devices.

To resolve this issue, you can enable the device to forward specific packets received from VXLAN tunnels in hardware without delivering them to the CPU.

Procedure

1.     Enter system view.

system-view

2.     Enable hardware forwarding for specific packets received from VXLAN tunnels.

forwarding vxlan-packet inner-protocol { ipv4 | ipv6 } *

By default, packets received from VXLAN tunnels are delivered to the CPU for processing.

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 the 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  ]

·     To display HPF trace information, use the following command in user view:

display hpf trace filter

Displaying the differences in FIB entries between two member devices

·     To display the differences in FIB entries between two member devices, 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 differences in FIB VN entries between two member devices, execute the following command in any view:

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