Contents

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

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

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

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

About load sharing·························································································································· 4

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

Enabling local-first load sharing······································································································· 4

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

Display and maintenance commands for load sharing······································································· 5

Loading sharing configuration examples··························································································· 5

Example: Configuring load sharing based on source and destination addresses·························· 5

 

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 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.

Procedure

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 or endpoints.

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 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 ] ]
Display the FIB table usage.	display fib usage

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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, 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.

Procedure

1.     Enter system view.

system-view

2.     Configure load sharing.

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 } ] { global | slot slot-number }

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.

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.

 

Task	Command
Display the load sharing mode in use.	display ip load-sharing mode slot slot-number
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 ] *

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Loading sharing configuration examples

Example: Configuring load sharing based on source and destination addresses

Network configuration

As shown in Figure 1, Switch A has two equal-cost routes to Switch B. Configure load sharing on Switch A to forward packets through Switch B to the destination IP address 1.2.3.4/24.

Figure 1 Network diagram

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Procedure

# On Switch A, assign Ten-GigabitEthernet 1/0/1 to VLAN 10, and Ten-GigabitEthernet 1/0/2 to VLAN 20.

<SwitchA> system-view

[SwitchA] vlan 10

[SwitchA-vlan10] port ten-gigabitethernet 1/0/1

[SwitchA-vlan10] quit

[SwitchA] vlan 20

[SwitchA-vlan20] port ten-gigabitethernet 1/0/2

[SwitchA-vlan20] quit

# On Switch A, configure IP addresses for VLAN-interface 10 and VLAN-interface 20.

[SwitchA] interface vlan-interface 10

[SwitchA-Vlan-interface10] ip address 10.1.1.1 24

[SwitchA-Vlan-interface10] quit

[SwitchA] interface vlan-interface 20

[SwitchA-Vlan-interface20] ip address 20.1.1.1 24

[SwitchA-Vlan-interface20] quit

# On Switch B, assign Ten-GigabitEthernet 1/0/1 to VLAN 10, and Ten-GigabitEthernet 1/0/2 to VLAN 20.

<SwitchB> system-view

[SwitchB] vlan 10

[SwitchB-vlan10] port ten-gigabitethernet 1/0/1

[SwitchB-vlan10] quit

[SwitchB] vlan 20

[SwitchB-vlan20] port ten-gigabitethernet 1/0/2

[SwitchB-vlan20] quit

# On Switch B, configure IP addresses for VLAN-interface 10 and VLAN-interface 20.

[SwitchB] interface vlan-interface 10

[SwitchB-Vlan-interface10] ip address 10.1.1.2 24

[SwitchB-Vlan-interface10] quit

[SwitchB] interface vlan-interface 20

[SwitchB-Vlan-interface20] ip address 20.1.1.2 24

[SwitchB-Vlan-interface20] quit

# On Switch A, configure two static routes to the destination IP address.

<SwitchA> system-view

[SwitchA] ip route-static 1.2.3.4 24 10.1.1.2

[SwitchA] ip route-static 1.2.3.4 24 20.1.1.2

[SwitchA] quit

# On Switch A, display FIB entries matching the destination IP address 1.2.3.4.

<SwitchA> display fib 1.2.3.4

Destination count: 1 FIB entry count: 2

Flag:

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

  R:Relay     F:FRR

Destination/Mask   Nexthop         Flag     OutInterface/Token       Label

1.2.3.0/24         10.1.1.2        USGR     Vlan10                   Null

1.2.3.0/24         20.1.1.2        USGR     Vlan20                   Null

# On Switch A, configure per-flow load sharing based on the source IP address and destination IP address.

<SwitchA> system-view

[SwitchA] ip load-sharing mode per-flow dest-ip src-ip global

Verifying the configuration

# Verify that Switch A implements load sharing.

<SwitchA> display counters outbound interface Ten-GigabitEthernet

Interface         Total (pkts)   Broadcast (pkts)   Multicast (pkts)  Err (pkts)

XGE1/0/1                 1045                  0                  0           0

XGE1/0/2                 1044                  0                  0           0