Contents

Basic IP forwarding on the device················································ 1

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

Displaying FIB table entries···································································································· 1

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

Configuration procedure········································································································ 3

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

Load sharing configuration example························································································ 3

Network requirements····································································································· 3

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

Verifying the configuration······························································································ 5

Basic IP forwarding on the device

Upon receiving a packet, the device uses the destination IP address of the packet to find a match from the forwarding information base (FIB) table, and 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:Useable   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        M-GE0/0/0                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 identity 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 comprises 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.

Displaying FIB table entries

Execute display commands in any view.

 

Task	Command
Display FIB entries.	display fib [ 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.

Configuration procedure

Per-flow load sharing allows the device to forward 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 source IP address, destination IP address, source port number, destination port number, IP protocol number, and ingress port.

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

To configure per-flow load sharing:

 

Step	Command	Remarks
1.     Enter system view.	system-view	N/A
2.     Configure per-flow load sharing.	ip load-sharing mode per-flow [ algorithm algorithm-number | [ dest-ip | dest-port | ingress-port | ip-pro | src-ip | src-port ] * ] [ slot slot-number ]	By default, the device performs per-flow load sharing based on the source IP address, destination IP address, source port number, destination port number, IP protocol number, ingress port, and VLAN.

 

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	By default, local-first load sharing is enabled.

 

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

 

Configuration procedure

# On Switch A, assign GigabitEthernet 1/0/5 to VLAN 10, and GigabitEthernet 1/0/6 to VLAN 20.

<SwitchA> system-view

[SwitchA] vlan 10

[SwitchA-vlan10] port GigabitEthernet 1/0/5

[SwitchA-vlan10] quit

[SwitchA] vlan 20

[SwitchA-vlan20] port GigabitEthernet 1/0/6

[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 1/0/5 to VLAN 10, and GigabitEthernet 1/0/6 to VLAN 20.

<SwitchB> system-view

[SwitchB] vlan 10

[SwitchB-vlan10] port GigabitEthernet 1/0/5

[SwitchB-vlan10] quit

[SwitchB] vlan 20

[SwitchB-vlan20] port GigabitEthernet 1/0/6

[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>dis fib 1.2.3.4

 

Destination count: 1 FIB entry count: 2

 

Flag:

  U:Useable   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

# On Switch A, display outbound traffic statistics.

[SwitchA] display counters outbound interface GigabitEthernet

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

GE1/0/1                     0                  0                  0           0

GE1/0/2                     0                  0                  0           0

GE1/0/3                     0                  0                  0           0

GE1/0/4                     0                  0                  0           0

GE1/0/5                  1045                  0                  0           0

GE1/0/6                  1044                  0                  0           0

The output shows that GigabitEthernet 1/0/5 and GigabitEthernet 1/0/6 receive almost the same number of packets. Load sharing is implemented.