Contents

Configuring IP forwarding basic settings························································ 2

About FIB table······························································································································· 2

Saving the IP forwarding entries to a file··························································································· 3

Enabling IPv4 fast traffic migration··································································································· 3

Enabling IPv4 FIB entry consistency check······················································································· 3

Enabling SNMP notifications for FIB events······················································································ 4

Enabling SNMP notifications for IP forwarding events······································································· 4

Enabling FIB logging······················································································································· 5

Display and maintenance commands for FIB table············································································ 5

Configuring load sharing··················································································· 5

About load sharing·························································································································· 5

Configuring load sharing mode········································································································ 5

Enabling local-first load sharing······································································································· 6

Enabling symmetric load sharing······································································································ 7

Display and maintenance commands for load sharing······································································· 7

Loading sharing configuration examples··························································································· 7

Example: Configuring load sharing based on source and destination addresses·························· 7

 

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 fast traffic migration

About this task

After this feature is enabled on a VLAN interface, the device immediately steers IPv4 traffic forwarded through the VLAN interface to other forwarding paths upon network topology changes or user port migrations. This reduces traffic disruption time and improves overall network response speed and user experience.

Procedure

1.     Enter system view.

system-view

2.     Enter VLAN interface view.

interface vlan-interface interface-number

3.     Enable IPv4 fast traffic migration.

ip forwarding fast-move

By default, IPv4 fast traffic migration is disabled.

Enabling IPv4 FIB entry consistency check

About this task

Packet drops or incorrect forwarding might occur when the IPv4 FIB entries in hardware are inconsistent with FIB entries configured in software. To prevent these issues, enable IPv4 FIB entry consistency check.

This feature compares all IPv4 FIB entries in software with the IPv4 FIB entries in hardware regularly. If the device detects an inconsistency, the device performs the following tasks:

·     Generates a log.

·     Updates the IPv4 FIB entry in hardware with the IPv4 FIB entry in software.

Procedure

1.     Enter system view.

system-view

2.     Enable IPv4 FIB entry consistency check.

fib consistency-check enable

By default, IPv4 FIB entry consistency check is disabled.

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 [ deliver-failed | ecmp-limit | entry-consistency | entry-limit ] *

By default, SNMP notifications for FIB events are enabled.

Enabling SNMP notifications for IP forwarding events

About this task

This feature enables the IP forwarding module to generate SNMP notifications for critical IP forwarding events. 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.

You can enable SNMP notifications for the following IP forwarding events as needed:

·     After you enable SNMP notifications about TTL timeout, the device checks the number of dropped packets at the specified time interval. An SNMP notification is generated and sent to the SNMP module when the number of dropped packets reaches or exceeds the specified threshold.

·     After you enable SNMP notifications about MBUF allocation failures, an SNMP notification is generated and sent to the SNMP module when MBUF allocation fails.

If you do not specify any parameters, the command enables all types of SNMP notifications for IP forwarding events.

After you disable the SNMP notifications for IP forwarding events, the device sends only logs to the device's information center module. In this case, you can configure the log output destinations and output rules to view the log information of the basic IPv6 modules. For more information about configuring the information center, see information center configuration in Network Management and Monitoring Configuration Guide.

Procedure

1.     Enter system view.

system-view

2.     Enable SNMP notifications for IP forwarding events.

snmp-agent trap enable ip-forwarding [ ttl-expired | mbuf-alloc ]

By default, SNMP notifications for IP forwarding events are enabled.

Enabling FIB logging

About this task

The logs are sent to the information center of the device. For the logs to be output correctly, you must also configure the information center on the device. For more information about information center configuration, see Network Management and Monitoring Configuration Guide.

To avoid memory consumption caused by log recording, you can use the undo fib log enable command to disable FIB logging.

Procedure

1.     Enter system view.

system-view

2.     Enable FIB logging.

fib log enable

By default, FIB logging is disabled.

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 ] ]
Display FIB table usage information.	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.

Restrictions and guidelines

·     When the traffic is not shared equally, you can use the seed and shift keywords to improve load sharing.

·     The load sharing hash seed feature does not take effect on unknown unicast packets.

·     The load sharing feature for IP Tunnel packets does not take effect on unknown unicast packets.

·     If per-flow load sharing based on the flow label of an IPv6 packet is enabled, MPLS packets with an inner IPv6 packet are not supported.If traffic is not shared equally, you can use the seed option and the shift shift-number option to adjust the algorithm result.

·     The load-sharing hash seed feature does not take effect for unknown unicast packets.

·     The load-sharing function for IP tunnel packets does not take effect for unknown unicast packets.

·     If IPv6 packets are encapsulated by MPLS, they do not support flow label-based per-flow 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 } ] | per-packet } { 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 ] } [ 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.

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.

 

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 ] } [ 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 GigabitEthernet 1/0/1 to VLAN 10, and GigabitEthernet 1/0/2 to VLAN 20.

<SwitchA> system-view

[SwitchA] vlan 10

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

[SwitchA-vlan10] quit

[SwitchA] vlan 20

[SwitchA-vlan20] port 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 GigabitEthernet 1/0/1 to VLAN 10, and GigabitEthernet 1/0/2 to VLAN 20.

<SwitchB> system-view

[SwitchB] vlan 10

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

[SwitchB-vlan10] quit

[SwitchB] vlan 20

[SwitchB-vlan20] port 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 GigabitEthernet

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

GE1/0/1                  1045                  0                  0           0

GE1/0/2                  1044                  0                  0           0