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

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

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

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

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

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

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

Configuration procedure················································································································································ 5

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

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: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        GE3/0/1                  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 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 [ vpn-instance vpn-instance-name ] [ ip-address [ mask | mask-length ] ]

 

If a routing protocol finds multiple equal-cost best routes to the same destination, the switch forwards packets over the equal-cost routes to implement load sharing.

When the link aggregation load sharing is not balanced, H3C recommends you use the link-aggregation global load-sharing mode command to specify load sharing criteria first. If the problem persists, use this feature in this chapter to adjust the algorithm for load sharing. For more information about load sharing criteria, see Layer 2—LAN Switching Configuration Guide.

Configuration procedure

When the number of equal-cost routes ≥ 8, select an algorithm according to the receiving interface location:

·     The receiving interfaces on non-consecutive cards—Use algorithm 1, 2, or 3.

·     The receiving interfaces on consecutive cards—Use algorithm 4, 5, or 6.

When the number of equal-cost routes ≤ 8, follow the guidelines as shown in Table 1 to choose an algorithm.

Table 1 Application scenario and the recommended algorithm number

Application scenario	Algorithm
Conditions in which neither of the following scenarios is applicable.	0
The following conditions are met: ·     The outbound interfaces include Layer 2 aggregation interfaces (except lite Layer 2 aggregate interfaces) or Layer 3 aggregation interfaces. ·     The receiving interfaces are not on consecutive cards. ·     Number of equal-cost routes = 8.	1
The following conditions are met: ·     The outbound interfaces include Layer 2 aggregation interfaces (except lite Layer 2 aggregate interfaces) or Layer 3 aggregation interfaces. ·     The receiving interfaces are not on consecutive cards. ·     8 > Number of equal-cost routes ≥ 4.	2
The following conditions are met: ·     The outbound interfaces include Layer 2 aggregation interfaces (except lite Layer 2 aggregate interfaces) or Layer 3 aggregation interfaces. ·     The receiving interfaces are not on consecutive cards. ·     4 > Number of equal-cost routes ≥ 2.	3
The following conditions are met: ·     The outbound interfaces include Layer 2 aggregation interfaces (except lite Layer 2 aggregate interfaces) or Layer 3 aggregation interfaces. ·     The receiving interfaces are on consecutive cards. ·     Number of equal-cost routes = 8.	4
The following conditions are met: ·     The outbound interfaces include Layer 2 aggregation interfaces (except lite Layer 2 aggregate interfaces) or Layer 3 aggregation interfaces. ·     The receiving interfaces are on consecutive cards. ·     8 > Number of equal-cost routes ≥ 4.	5
The following conditions are met: ·     The outbound interfaces include Layer 2 aggregation interfaces (except lite Layer 2 aggregate interfaces) or Layer 3 aggregation interfaces. ·     The receiving interfaces are on consecutive cards. ·     4 > Number of equal-cost routes ≥ 2.	6

 

For example, algorithm 5 is the best choice for the following application scenario:

·     The number of equal-cost routes is 6.

·     The receiving interfaces are on the cards in slot 3 and slot 4.

·     The output interfaces are Layer 2 aggregation interfaces.

To configure load sharing:

 

Step	Command	Remarks
1.     Enter system view.	system-view	N/A
2.     Configure load sharing.	·     Distributed devices–In standalone mode: ip load-sharing mode per-flow algorithm algorithm-number  [ slot slot-number ] ·     Distributed devices–In IRF mode: ip load-sharing mode per-flow algorithm algorithm-number [ chassis chassis-number slot slot-number ]	The default algorithm is 0. The slot slot-number and chassis chassis-number slot slot-number options are not supported in the current software version, and is reserved for future support.

 

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 Ten-GigabitEthernet 2/0/5 to VLAN 10, and Ten-GigabitEthernet 2/0/6 to VLAN 20.

<SwitchA> system-view

[SwitchA] vlan 10

[SwitchA-vlan10] port Ten-GigabitEthernet 2/0/5

[SwitchA-vlan10] quit

[SwitchA] vlan 20

[SwitchA-vlan20] port Ten-GigabitEthernet 2/0/6

[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 Ten-GigabitEthernet 2/0/5 to VLAN 10, and Ten-GigabitEthernet 2/0/6 to VLAN 20.

<SwitchB> system-view

[SwitchB] vlan 10

[SwitchB-vlan10] port Ten-GigabitEthernet 2/0/5

[SwitchB-vlan10] quit

[SwitchB] vlan 20

[SwitchB-vlan20] port Ten-GigabitEthernet 2/0/6

[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, specify algorithm 0 for per-flow load sharing.

<SwitchA> system-view

[SwitchA] ip load-sharing mode per-flow algorithm 0

[SwitchA] quit

Verifying the configuration

# Verify that Switch A implements load sharing.

<SwitchA> system-view

[H3C]dis counters outbound interface Ten-GigabitEthernet

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

XGE2/0/1                     0                  0                  0           0

XGE2/0/2                     0                  0                  0           0

XGE2/0/3                     0                  0                  0           0

XGE2/0/4                     0                  0                  0           0

XGE2/0/5                  1045                  0                  0           0

XGE2/0/6                  1044                  0                  0           0