Contents

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

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

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

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

Displaying FIB table entries·············································································································· 2

Configuring load sharing··················································································· 3

Configuring load sharing·················································································································· 3

Enabling local-first load sharing······································································································· 3

Enabling symmetric load sharing······································································································ 3

Displaying and maintaining load sharing··························································································· 4

Load sharing configuration example································································································· 4

Network requirements··············································································································· 4

Configuration procedure··········································································································· 4

Verifying the configuration········································································································ 6

 

Configuring IP forwarding basic settings

The device uses the destination IP address of a received packet to find a match from the forwarding information base (FIB) table. It then uses the matching entry to forward the packet.

FIB table

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 FIB table entries. The following example displays the entire FIB table.

<Sysname> display fib

 

Destination count: 4 FIB entry count: 4

 

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        XGE1/0/1                 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.

Saving the IP forwarding entries to a file

The feature automatically creates the file if you specify a nonexistent file. If the file already exists, this feature overwrites the file content.

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.

To save the IP forwarding entries to a file:

 

Task	Command	Remarks
Specify a file to save the IP forwarding entries.	ip forwarding-table save filename filename	Executing this command triggers one-time saving of the IP forwarding entries. This command can be executed in any view.

 

Enabling split horizon forwarding

IMPORTANT: This feature is available in Release 2612 and later.

 

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

To enable split horizon forwarding:

 

Step	Command	Remarks
1.     Enter system view.	system-view	N/A
2.     Enable split horizon forwarding.	forwarding split-horizon	By default, split horizon forwarding is disabled.

 

Displaying FIB table entries

Execute display commands in any view.

 

Task	Command
Display FIB entries.	display fib [ vpn-instance vpn-instance-name ] [ ip-address [ mask | mask-length ] ]

 

 

Configuring 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

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 per-flow criteria cannot distinguish flows, you can use the algorithm keyword to specify an algorithm to identify flows.

To configure load sharing:

 

Step	Command	Remarks
1.     Enter system view.	system-view	N/A
2.     Configure load sharing.	ip load-sharing mode per-flow [ algorithm algorithm-number [ seed seed-number ] [ shift shift-number ] | [ dest-ip | dest-port | ip-pro | src-ip | src-port | ingress-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.

 

Enabling local-first load sharing

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.

To enable local-first load sharing:

 

Step	Command	Remarks
1.     Enter system view.	system-view	N/A
2.     Enable local-first load sharing.	ip load-sharing local-first enable	Local-first load sharing is enabled.

 

Enabling symmetric load sharing

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

Before you enable symmetric load sharing, make sure the traffic identification criteria does not include ingress port for load sharing. If the ingress port criterion is included, symmetric load sharing does not take effect.

To enable symmetric load sharing:

 

Step	Command	Remarks
1.     Enter system view.	system-view	N/A
2.     Enable symmetric load sharing.	ip load-sharing symmetric enable	By default, symmetric load sharing is disabled.

 

Displaying and maintaining load sharing

Execute display commands in any view and reset commands in user view.

When you configure the display ip load-sharing path command, make sure the options are the same as those in the ip load-sharing mode command. If the options are not consistent, the path displayed by this command might be different from the real path for load sharing.

 

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

 

Load sharing configuration example

Network requirements

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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Configuration 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

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