Contents

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

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

Saving the IP forwarding entries to a file··························································································· 2

Enabling IPv4 packet forwarding on an interface with no IPv4 address configured······························ 2

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

Enabling SNMP notifications for FIB events······················································································ 3

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

Configuring load sharing··················································································· 4

Configuring load sharing mode········································································································ 4

Enabling local-first load sharing······································································································· 5

Enabling symmetric load sharing······································································································ 5

Display and maintenance commands for load sharing······································································· 6

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: 8 FIB entry count: 8

Flag:

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

  R:Relay     F:FRR

Destination/Mask   Nexthop         Flag     OutInterface/Token       Label

0.0.0.0/32         127.0.0.1       UH       InLoop0                  Null

127.0.0.0/8        127.0.0.1       U        InLoop0                  Null

127.0.0.0/32       127.0.0.1       UH       InLoop0                  Null

127.0.0.1/32       127.0.0.1       UH       InLoop0                  Null

127.255.255.255/32 127.0.0.1       UH       InLoop0                  Null

224.0.0.0/4        0.0.0.0         UB       NULL0                    Null

224.0.0.0/24       0.0.0.0         UB       NULL0                    Null

255.255.255.255/32 127.0.0.1       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

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.

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, the IPv4 packet forwarding is disabled on the interface that has no IPv4 address configured.

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.

You can enable specific SNMP notifications for FIB events as needed. If you do not specify any SNMP notification types, the command enables all types of SNMP notifications.

·     With ecmp-limit specified, when the number of ECMP routes learned by a module exceeds the upper limit, the device sends an SNMP notification that carries the module number to the SNMP module.

·     With entry-consistency specified, if the FIB software and hardware entries on a module are inconsistent, the device sends an SNMP notification that carries the module number to the SNMP module.

·     With entry-limit specified, when the number of FIB entries exceeds the upper limit, the device sends an SNMP notification that carries the FIB entry module name to the SNMP module.

·     With deliver-failed specified, when FIB entry deployment to the hardware fails, the device sends an SNMP notification that carries the entry VRF, IP address type, IP address, mask, and failure reason 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 [ deliver-failed | ecmp-limit | entry-consistency | entry-limit ] *

By default, SNMP notifications for FIB events are enabled.

Display and maintenance commands for FIB table

Execute display commands in any view.

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Configuring 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, IP protocol number, and ingress port.

In a complex network, when the traffic is not load shared equally, you can use the algorithm keyword to specify an algorithm to improve the load sharing.

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

Restrictions and guidelines

·     For MPLS packets, the device only supports per-flow load sharing based on their source IP addresses or destination IP addresses.

·     For the S12500G-AF switch series, per-packet load sharing only takes effect on the SF interface modules. In VXLAN networks, per-packet load sharing cannot take effect on any interface modules (including the SF interface modules). In VXLAN networks, per-packet load sharing cannot take effect on the S12500CR switch series.

·     Per-packet load sharing is configurable only if the ECMP mode is Normal. For more information about ECMP modes, see IP routing basics commands in Layer 3—IP Routing Command Reference.

·     Enabling per-packet load sharing will cause packet disorder. As a best practice, use this feature only when packet disorder does not affect services.

·     If the load sharing mode specified by the ip load-sharing mode command is per-packet, the path displayed by the display ip load-sharing path command will be different from the real path for load sharing.

·     By default, the device performs per-flow load sharing based on the following criteria: source IP address, destination IP address, source port number, destination port number, and IP protocol number. The first fragment and the other fragments of the same packet might be forwarded through different output ports. When the S12500G-AF switch series uses SE interface modules, the result of packet fragment reassembly might be strongly related to the packet forwarding path. In this situation, packet fragment reassembly might fail when fragments of the same packet are forwarded along different forwarding paths. To resolve this issue, re-execute the ip load-sharing mode command without specifying the dest-port and src-port keywords.

Procedure

1.     Enter system view.

system-view

2.     Configure load sharing.

In standalone mode:

ip load-sharing mode { per-flow [ algorithm algorithm-number [ seed seed-number ] [ shift shift-number ] | [ dest-ip | dest-port | ingress-port | ip-pro | src-ip | src-port ] * | tunnel { inner | outer } ] | per-packet } { global | slot slot-number }

In IRF mode:

ip load-sharing mode { per-flow [ algorithm algorithm-number [ seed seed-number ] [ shift shift-number ] | [ dest-ip | dest-port | ingress-port | ip-pro | src-ip | src-port ] * | tunnel { inner | outer } ] | per-packet } { chassis chassis-number slot slot-number | global }

By default, the device performs per-flow load sharing based on the following criteria: source IP address, destination IP address, source port number, destination port number, IP protocol number, and ingress port.

3.     Display the load sharing path selected for a flow.

display ip load-sharing path ingress-port interface-type interface-number packet-format { ipv4oe dest-ip ip-address [ src-ip ip-address ] | ipv6oe dest-ipv6 ipv6-address [ src-ipv6 ipv6-address | flow-label flow-label ] } [ dest-port port-id | ip-pro protocol-id | src-port port-id | vpn-instance vpn-instance-name ] *

The option settings in this command must match both the options displayed in the display ip load-sharing mode command and the field values in load shared packets. If the option settings do not meet the requirement, the path displayed by this command might be different from the real path for load sharing.

Enabling local-first load sharing

About this task

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.

Enabling symmetric load sharing

About this task

Symmetric load sharing ensures that bidirectional traffic specific to a source and destination address pair flow along the same path.

Hardware and feature compatibility

For the S12500G-AF series switches, only the SF series interface modules support this feature.

Restrictions and guidelines

Symmetric load sharing takes effect only on known unicast packets.

Procedure

1.     Enter system view.

system-view

2.     Enable symmetric load sharing.

ip load-sharing symmetric enable

By default, symmetric load sharing is disabled.

Display and maintenance commands for load sharing

Execute display commands in any view.

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