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The Flow-Based per Port-Channel Load Balancing feature allows different flows of traffic over a Gigabit EtherChannel (GEC)
interface to be identified based on the packet header and then mapped to the different member links of the port channel. This
feature enables you to apply flow-based load balancing and VLAN-manual load balancing to specific port channels.
Restrictions for Flow-Based
per Port-Channel Load Balancing
Supports up to 64
GEC interfaces.
Supports up to 14
member links per GEC interface.
Note
This feature achieves load balancing of MPLS traffic only by using source IP address and destination IP address. The MPLS
label is not considered for load balancing.
Information About Flow-Based per Port-Channel Load Balancing
Flow-Based Load Balancing
Flow-based load balancing identifies different flows of traffic based on the key fields in the data packet. For example, IPv4
source and destination IP addressees can be used to identify a flow. The various data traffic flows are then mapped to the
different member links of a port channel. After the mapping is done, the data traffic for a flow is transmitted through the
assigned member link. The flow mapping is dynamic and changes when there is any change in the state of a member link to which
a flow is assigned. The flow mappings can also change if member links are added to or removed from the GEC interface. Multiple
flows can be mapped to each member link.
Buckets for Flow-Based Load
Balancing
Load balancing
dynamically maps traffic flows to the member links of a GEC interface through
the concept of buckets. The various defined traffic flows are mapped to the
buckets and the buckets are evenly distributed among the member links. Each
port channel maintains 16 buckets, with one active member link associated with
each bucket. All traffic flows mapped to a bucket use the member link to which
the bucket is assigned.
The router creates
the buckets-to-member links mappings when you apply flow-based load balancing
to a port channel and the port channel has at least one active member link. The
mappings are also created when the first member link is added, or comes up, and
the load-balancing method is set to flow-based.
When a member link
goes down or is removed from a port channel, the buckets associated with that
member link are redistributed among the other active member links in a
round-robin fashion. When a member link comes up or is added to a port channel,
some of the buckets associated with other links are assigned to this link.
The figure below
illustrates an example of 16 buckets distributed among three member links. The
numbers shown in the buckets are the bucket IDs. Note that the first member
link has an extra bucket.
Figure 1. Example of 16 Buckets Mapped
to Three Member Links
If you change the
load-balancing method, the bucket-to-member link mappings for flow-based load
balancing are deleted. The mappings are also deleted if the port channel is
deleted or the last member link in the port channel is deleted or goes down.
Load Balancing on Port Channels
GEC interfaces can use either dynamic flow-based load balancing or VLAN-manual load balancing. You can configure the load-balancing
method globally for all port channels or directly on specific port channels. The global configuration applies only to those
port channels for which you have not explicitly configured load balancing. The port-channel configuration overrides the global
configuration.
Flow-based load balancing is enabled by default at the global level. You must explicitly configure VLAN load balancing or
the load-balancing method is flow-based.
For more information about configuring VLAN load balancing, see the module VLAN Mapping to Gigabit EtherChannel (GEC) Member
Links.
The table below lists the load-balancing method that is applied to port channels based on the configuration:
The table below lists the configuration that results if you change the global load-balancing method.
Table 2. Results When Global Configuration Changes
Port-Channel Configuration
Global Configuration
Action Taken at Port Channel
–
From
To
–
Not configured
Not configured
VLAN-manual
Changed from flow-based to VLAN-manual
VLAN-manual
Not configured
Changed from VLAN-manual to flow-based
Configured
Any
Any
No change
The table below lists the configuration that results if you change the port-channel load-balancing method.
Table 3. Results When Port-Channel Configuration Changes
Global Configuration
Port-Channel Configuration
Action Taken at Port Channel
–
From
To
–
Not configured
Not configured
VLAN-manual
Changed from flow-based to VLAN-manual
Not configured
Flow-based
No action taken
VLAN-manual
Flow-based
Changed from VLAN-manual to flow-based
VLAN-manual
Not configured
Changed from VLAN-manual to flow-based
Flow-based
VLAN-manual
Changed from flow-based to VLAN-manual
Flow-based
Not configured
No action taken
VLAN-manual
Not configured
VLAN-manual
No action taken
Not configured
Flow-based
Changed from VLAN-manual to flow-based
VLAN-manual
Flow-based
Changed from VLAN-manual to flow-based
VLAN-manual
Not configured
No action taken
Flow-based
VLAN-manual
Changed from flow-based to VLAN-manual
Flow-based
Not configured
Changed from flow-based to VLAN-manual
How to Enable Flow-Based per Port-Channel Load Balancing
Configuring Load Balancing on a Port Channel
To configure load balancing on a port channel, perform the following steps. Repeat these steps for each GEC interface.
Before you begin
If you have already configured your desired load-balancing method globally and want to use that method for all port channels,
you need not perform this task. To configure load balancing globally, use the port-channelload-balancingvlan-manual command. If you do not configure the global command, flow-based load balancing is applied to all port channels.
SUMMARY STEPS
enable
configureterminal
interfaceport-channelchannel-number
load-balancing {flow | vlan}
end
DETAILED STEPS
Command or Action
Purpose
Step 1
enable
Example:
Router> enable
Enables privileged EXEC mode.
Enter your password if prompted.
Step 2
configureterminal
Example:
Router# configure terminal
Enters global configuration mode.
Step 3
interfaceport-channelchannel-number
Example:
Router(config)# interface port-channel 1
Enters interface configuration mode and defines the interface as a port channel.
Step 4
load-balancing {flow | vlan}
Example:
Router(config-if)# load-balancing flow
Applies a load-balancing method to the specific port channel.
If you do not configure this command, the port channel uses the global load-balancing method configured with the port-channelload-balancingvlan-manual command. The global default is flow-based.
Step 5
end
Example:
Router(config-if)# end
Exits configuration mode.
Verifying Load-Balancing Configuration on a GEC Interface
Use these show commands to verify the load-balancing configuration and to display information about the bucket distribution
on the port channel. You can use these commands in any order.
Use this command to verify the configuration of the port channel.
Example:
Router# show running-config interface port-channel 1
Building configuration...
Current configuration : 88 bytes
!
interface Port-channel1
ip address 10.1.1.1 255.0.0.0
no negotiation auto
load-balancing flow
end
Step 2
showetherchannelload-balancing
Use this command to display the load-balancing method applied to each port channel. The following example shows output for
a configuration with load balancing set globally to VLAN-manual and set to flow-based on port channel 1:
Example:
Router# show etherchannel load-balancing
EtherChannel Load-Balancing Method:
Global LB Method: vlan-manual
Port-Channel: LB Method
Port-channel1 : flow-based
Use this command to display the bucket distribution currently in use. The following example shows output for an interface
with load balancing set to flow-based:
Example:
Router(config)# show interface port-channel 2 etherchannel
All IDBs List contains 3 configured interfaces
Port: GigabitEthernet2/1/6 (index: 0)
Port: GigabitEthernet2/1/7 (index: 1)
Port: GigabitEthernet2/1/0 (index: 2)
Active Member List contains 1 interfaces
Port: GigabitEthernet2/1/0
Passive Member List contains 2 interfaces
Port: GigabitEthernet2/1/6
Port: GigabitEthernet2/1/7
Load-Balancing method applied: flow-based
Bucket Information for Flow-Based LB:
Interface: Buckets
GigabitEthernet2/1/0:
Bucket 0 , Bucket 1 , Bucket 2 , Bucket 3
Bucket 4 , Bucket 5 , Bucket 6 , Bucket 7
Bucket 8 , Bucket 9 , Bucket 10, Bucket 11
Bucket 12, Bucket 13, Bucket 14, Bucket 15
Configuration Examples for Flow-Based per Port-Channel Load Balancing
Flow-Based Load Balancing Example
The following example shows a configuration where flow-based load balancing is configured on port-channel 2 while the VLAN-manual
method is configured globally:
!
no aaa new-model
port-channel load-balancing vlan-manual
ip source-route
.
.
.
interface Port-channel2
ip address 10.0.0.1 255.255.255.0
no negotiation auto
load-balancing flow
!
interface Port-channel2.10
ip rsvp authentication key 11223344
ip rsvp authentication
!
interface Port-channel2.50
encapsulation dot1Q 50
!
interface GigabitEthernet2/1/0
no ip address
negotiation auto
cdp enable
channel-group 2
!
Information About Five-Tuple Hash Support for GEC Flow-based Load Balancing
The five-tuple hash support for gigabit etherchannel (GEC) flow-based load balancing feature decides which member link to
use for routing traffic based on the following five parameters:
Source IP address
Destination IP address
Source Port
Destination Port
Protocol ID (type of protocol: TCP/UDP)
Earlier, the GEC flow-based load balancing feature was applicable only for layer 3 (network layer). With the five-tuple hash
support, it’s applicable for layer 4 (TCP/IP layer) also. But it is supported only for the TCP and UDP, layer 4 protocols.
Restrictions for Five-Tuple Hash Support for GEC Flow-based Load Balancing
The five-tuple hash support for GEC flow-based load balancing feature is not supported for MPLS traffic.
Configuring Five-Tuple Hash Support for GEC Flow-based Load Balancing
Use the port-channel load-balance-hash-algo command to enable the five-tuple hash support for GEC flow-based load balancing feature.
The following example shows how to configure a five-tuple hash support for GEC flow-based load balancing feature:
Device (config)# port-channel load-balance-hash-algo ?
src-dst-ip Source XOR Destination IP Addr
src-dst-mixed-ip-port Source XOR Destination Port, IP addr
The src-dst-mixed-ip-port option specifies load distribution based on the hash value obtained from the calculation of five parameters: source ip address,
destination ip address, source port, destination port, and L4 protocol.
Example
Additional References
The following sections provide references related to the Flow-Based per Port-Channel Load Balancing feature.
No new or modified standards are supported by this feature, and support for existing standards has not been modified by this
feature.
--
MIBs
MIB
MIBs Link
No new or modified MIBs are supported by this feature, and support for existing MIBs has not been modified by this feature.
To locate and download MIBs for selected platforms, Cisco IOS XE software releases, and feature sets, use Cisco MIB Locator
found at the following URL:
No new or modified RFCs are supported by this feature, and support for existing standards has not been modified by this feature.
--
Technical Assistance
Description
Link
The Cisco Support website provides extensive online resources, including documentation and tools for troubleshooting and
resolving technical issues with Cisco products and technologies.
To receive security and technical information about your products, you can subscribe to various services, such as the Product
Alert Tool (accessed from Field Notices), the Cisco Technical Services Newsletter, and Really Simple Syndication (RSS) Feeds.
Access to most tools on the Cisco Support website requires a Cisco.com user ID and password.
Feature Information for Flow-Based per Port-Channel Load Balancing
The following table provides release information about the feature or features described in this module. This table lists
only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise,
subsequent releases of that software release train also support that feature.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco
Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.
Table 4. Feature Information for Flow-Based per Port-Channel Load Balancing
Feature Name
Releases
Feature Information
Flow-Based per Port-Channel Load Balancing
Cisco IOS XE Release 2.5
This feature allows different flows of traffic over a GEC interface to be identified and mapped to the different member links.
It also enables you to apply load balancing to specific port channels.
The following commands were introduced or modified:
load-balancing,
port-channelload-balancingvlan-manual,
showetherchannelload-balancing,showinterfacesport-channeletherchannel.
IPv6 Loadbalancing on GEC
Cisco IOS XE Release 3.4S
The IPv6 Loadbalancing on GEC feature provides load balancing for IPv6 traffic on Gigabit EtherChannel.
Five-Tuple Hash Support for GEC Flow-based Load Balancing
Cisco IOS XE Everest 16.4.1
The five-tuple hash support for gigabit etherchannel (GEC) flow-based load balancing feature decides which member link to
use for routing traffic based on the hash value obtained from the calculation of 5 parameters: source ip address, destination
ip address, source port, destination port, and L4 protocol.
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