Contents

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

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

Saving the IP forwarding entries to a file··························································································· 1

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

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

Enabling FIB route switching optimization························································································· 3

Specifying the maximum number of FIB entries on an interface module·············································· 3

Performing one-time FIB entry synchronization·················································································· 4

Enabling FIB logging······················································································································· 4

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

Enabling SNMP notifications for IP forwarding events······································································· 5

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

Configuring load sharing··················································································· 6

About load sharing·························································································································· 6

Configuring per-packet or per-flow load sharing················································································ 6

Enabling bandwidth-based 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

 

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        XGE3/0/1                  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—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.

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

1.     Enter system view.

system-view

2.     Enter interface view.

interface interface-type interface-number

3.     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.

Enabling FIB route switching optimization

About this task

This feature is applicable to scenarios with high service traffic sustainability requirements. It enables the device to keep using the current route until the new route becomes available, instead of disconnecting the current route directly. This prevents packet loss caused by route switch, which might take hundreds of milliseconds.

The device can keep using the current route for a maximum of 10 seconds.

Procedure

1.     Enter system view.

system-view

2.     Enable FIB route switching optimization.

fib switch-enhance

By default, FIB route switching optimization is disabled.

Specifying the maximum number of FIB entries on an interface module

About this task

By default, the maximum number of FIB entries on an interface module is the maximum number of FIB entries supported by the device. To save memory resources, you can perform this task to decrease the maximum number of FIB entries on an interface module.

Restrictions and guidelines

If the value for the max-number argument exceeds the maximum number supported by the device, the configuration does not take effect on interface modules. The maximum number supported by the device is then applied to the interface modules.

If the number of FIB entries has reached max-number on an interface module, the module stops accepting new FIB entries issued by the MPU. The existing services on the module are not affected. If the MPU deletes some old FIB entries and notifies the interface module to delete the entries, the interface module can accept new FIB entries until the upper limit is reached again.

Procedure

1.     Enter system view.

system-view

2.     Specify the maximum number of FIB entries on an interface module.

fib max-number max-number slot slot-number

By default, the maximum number of FIB entries on an interface module is the maximum number of FIB entries supported by the device.

Performing one-time FIB entry synchronization

About this task

Perform this task to synchronize FIB entries from the MPU to the specified interface module.

Restrictions and guidelines

If the maximum number of IPv4 or IPv6 FIB entries (specified by using the fib max-number or ipv6 fib max-number command) is reached on the interface module, the module stops accepting new entries.

Procedure

1.     Enter system view.

system-view

2.     Perform one-time FIB entry synchronization.

fib smooth slot slot-number

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.

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.

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.

Procedure

1.     Enter system view.

system-view

2.     Enable SNMP notifications for IP forwarding events.

snmp-agent trap enable ip-forwarding

By default, SNMP notifications for IP forwarding 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 ] ] [ slot slot-number ]
Display FIB entry statistics.	display fib count [ all | vpn-instance vpn-instance-name ] slot slot-number

‌

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 per-packet or per-flow load sharing

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, source MAC address, destination IP address, destination MAC address, source port number, destination port number, IP protocol number, and ingress port. You can also configure per-flow load sharing for IP tunnel packets.

In a complex network, when the criteria cannot distinguish flows, you can use the algorithm keyword to specify an algorithm to identify flows.

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

Restrictions and guidelines

The ip-pro keyword is not supported is not supported on the device.

On the device, the per-flow load sharing modes take effect in the following order:

1.     Algorithm-based per-flow load sharing configured globally or on the specified card (specified by the algorithm algorithm-number option).

2.     Per-flow load sharing with a random combination of the dest-ip, dest-mac, dest-port, src-ip, src-mac, and src-port keywords on the specified card.

3.     Global per-flow load sharing with a random combination of the dest-ip, dest-mac, dest-port, src-ip, src-mac, and src-port keywords.

4.     Global default load sharing mode.

Procedure

1.     Enter system view.

system-view

2.     Configure load sharing.

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

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

Table 1 shows the default load sharing modes.

Table 1 Default load sharing modes

Packet type	Default load sharing mode
IP unicast packets	dest-ip, src-ip, dest-port, src-port
IP multicast packets	dest-ip, src-ip, dest-port, src-port
Layer 2 frames	dest-mac, src-mac
MPLS L3VPN packets	dest-ip, src-ip, dest-port, src-port
MPLS L2VPN packets	·     IP packets: dest-ip, src-ip, dest-port, src-port ·     Other packets: dest-mac, src-mac
MPLS LSPs	·     IP packets: mpls-label1, mpls-label2, dest-ip, src-ip, dest-port, src-port ·     Other packets: mpls-label1, mpls-label2, dest-mac, src-mac
Other MPLS packets	mpls-label1, mpls-label2
IP tunnel packets	·     IP packets: inner dest-ip, inner src-ip, inner src-port, inner dest-port ·     Non-termination MPLS packets: mpls-label1, mpls-label2

‌

Enabling bandwidth-based load sharing

About this task

This feature load shares flow traffic among multiple output interfaces based on their load percentages. The device calculates the load percentage for each output interface in terms of the interface expected bandwidth.

Devices that run load sharing protocols, such as Locator/ID Separation Protocol (LISP), implement load sharing based on the ratios defined by these protocols.

Procedure

1.     Enter system view.

system-view

2.     Enable IPv4 bandwidth-based load sharing.

bandwidth-based-sharing

By default, the IPv4 bandwidth-based load sharing is disabled.

3.     (Optional.) Configure the expected bandwidth of the interface.

a.     Enter interface view.

interface interface-type interface-number

b.     Configure the expected bandwidth of the interface.

bandwidth bandwidth

By default, the expected bandwidth is the physical bandwidth of the interface.

Loading sharing configuration examples

Example: Configuring load sharing based on source and destination addresses

Network configuration

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

Figure 1 Network diagram

‌

Procedure

# On Router A, assign IP addresses to interfaces.

<RouterA> system-view

[RouterA] interface ten-gigabitethernet 3/0/1

[RouterA-Ten-GigabitEthernet3/0/1] ip address 10.1.1.1 24

[RouterA-Ten-GigabitEthernet3/0/1] quit

[RouterA] interface ten-gigabitethernet 3/0/2

[RouterA-Ten-GigabitEthernet3/0/2] ip address 20.1.1.1 24

[RouterA-Ten-GigabitEthernet3/0/2] quit

# On Router B, assign IP addresses to interfaces.

<RouterB> system-view

[RouterB] interface ten-gigabitethernet 3/0/1

[RouterB-Ten-GigabitEthernet3/0/1] ip address 10.1.1.2 24

[RouterB-Ten-GigabitEthernet3/0/1] quit

[RouterB] interface ten-gigabitethernet 3/0/2

[RouterB-Ten-GigabitEthernet3/0/2] ip address 20.1.1.2 24

[RouterB-Ten-GigabitEthernet3/0/2] quit

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

[RouterA] ip route-static 1.2.3.4 24 10.1.1.2

[RouterA] ip route-static 1.2.3.4 24 20.1.1.2

[RouterA] quit

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

<RouterA> display fib 1.2.3.4

 

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     XGE3/0/1                  Null

1.2.3.0/24         20.1.1.2        USGR     XGE3/0/2                  Null

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

<RouterA> system-view

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

[RouterA] quit

Verifying the configuration

# Verify that Router A implements load sharing.

<RouterA> display counters outbound interface Ten-GigabitEthernet

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

XGE3/0/1                  1045                  0                  0           0

XGE3/0/2                  1044                  0                  0           0