Information About Cisco Catalyst SD-WAN EtherChannel
An EtherChannel provides fault-tolerant high-speed links between switches, routers, and servers. You can use the EtherChannel to increase bandwidth between the wiring closets and the data center, and also deploy it at any place in a network where bottlenecks are likely to occur. An EtherChannel provides automatic recovery for the loss of a link by redistributing the load across the remaining links. If a link fails, an EtherChannel redirects traffic from the failed link to the remaining links in the channel.
An EtherChannel comprises a channel group and a port-channel interface. The channel group binds physical ports to the port-channel interface. Configuration changes applied to the port-channel interface apply to all the physical ports bound together in the channel group.
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Using EtherChannels in a network provides increased bandwidth and resilience.
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Bandwidth: An EtherChannel allows multiple links to be combined into one logical link. Because an EtherChannel offers redundancy of links, you can configure EtherChannels to increase the speed in a network.
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Resilience: An EtherChannel also provides network resilience. Even if a link within an EtherChannel fails, traffic that is previously carried over the failed link switches to the remaining links within the EtherChannel. Thus, EtherChannel provides automatic recovery for the loss of a link by redistributing the load across the remaining links.
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The number of supported port channels differs based on the specific device model.
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The number of supported member interfaces for a port channel differs based on the specific device model.
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EtherChannel supports the following combinations:
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Two active links
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Active and passive links
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Single member link
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Loopback interface in bind or unbind mode to the port channel
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Starting from Cisco IOS XE Catalyst SD-WAN Release 17.13.1a and Cisco Catalyst SD-WAN Manager Release 20.13.1, EtherChannels configured on the transport side support the following:
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Control and management connections (DTLS, OMP) to Cisco Catalyst SD-WAN Manager, Cisco Catalyst SD-WAN Validator, and Cisco Catalyst SD-WAN Controller
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IPSEC tunnels for data traffic
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IPv4 forwarding
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L2 TLOC extension
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Explicit ACL (Access Control Lists)
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Implicit ACL on a port channel TLOC
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IPv4 static routing
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Loopback TLOC (ability to bind loopback to port channel)
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Port channel sub-interfaces
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Control policies on Cisco Catalyst SD-WAN Controller
Starting from Cisco IOS XE Catalyst SD-WAN Release 17.14.1a and Cisco Catalyst SD-WAN Manager Release 20.14.1, EtherChannels configured on the transport side support the following:
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IPv6 for EtherChannels, allowing for the transmission of IPv6 traffic across aggregated links.
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Handling traffic through Generic Routing Encapsulation (GRE) tunnels, facilitating the encapsulation of various network protocols.
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Advanced routing protocols such as OSPF and BGP over EtherChannels enables dynamic routing in Cisco Catalyst SD-WAN.
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NAT-DIA across EtherChannels, providing direct internet access by converting private IP addresses to public ones for efficient internet-bound traffic routing. For more information, see Configure NAT.
EtherChannel in Cisco Catalyst SD-WAN
To create an EtherChannel, begin by configuring a port channel. A port channel is a logical interface on a Cisco IOS XE Catalyst SD-WAN device. After you create an EtherChannel, the configuration changes that are applied to the port-channel interface are also applied to all the physical ports assigned to the port-channel interface.
The maximum number of interfaces that can be combined into a single EtherChannel using LACP is eight, although the actual limit may depend on the specific model of the device.
You can configure an EtherChannel using one these methods:
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Link Aggregation Control Protocol (LACP) mode
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Static mode
Use the LACP mode to configure an EtherChannel if it is supported on both ends of a device. If either of the device does not support LACP mode, use a static mode to configure an EtherChannel.
LACP Mode
LACP facilitates the automatic creation of EtherChannels by exchanging LACP packets between the Ethernet ports.
This table shows the user-configurable EtherChannel LACP modes.
Mode |
Description |
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active |
Places a port in an active negotiating state in which the port starts negotiations with other ports by sending LACP packets. |
passive |
Places a port in a passive negotiating state in which the port responds to the packets that it receives, but does not start LACP packet negotiation. This setting minimizes the transmission of LACP packets. |
Both the active and passive modes enable ports to negotiate with partner ports based on port speed.
Ports can form an EtherChannel when they are in different LACP modes as long as the modes are compatible. For example:
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A port in the active mode can form an EtherChannel with another port that is in the active or passive mode.
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A port in the passive mode cannot form an EtherChannel with another port that is also in the passive mode because neither port starts LACP negotiation.
In addition to the standard LACP configuration, the following LACP-related commands are supported:
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lacp min-bundle
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lacp max-bundle
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lacp system-priority
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lacp port-priority
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lacp fast-switchover
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lacp rate fast
Static Mode
You can manually create an EtherChannel by using the interface port-channel command in the global configuration mode. You then use the channel-group interface command in the global configuration mode to assign an interface to the EtherChannel. After you configure an EtherChannel, the configuration changes applied to the port-channel interface are applied to all the physical ports assigned to the port-channel interface. Unlike an LACP mode, in a static mode, no packets are sent for negotiations with the other ports. Instead, you must manually configure the ports as part of an EtherChannel.
Information related to LACP on port-channel interfaces can be obtained using the show lacp command. See show lacp.
EtherChannel Load Balancing
An EtherChannel balances traffic load across the links in a channel. You can specify one of several different load-balancing modes. EtherChannels can use either dynamic flow-based load balancing or virtual LAN (VLAN) manual load balancing.
You can configure the load-balancing method globally for all the 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.
The following load-balancing methods are supported on Cisco IOS XE Catalyst SD-WAN devices:-
Flow-Based
VLAN-Based
Flow-Based Load Balancing
Flow-based load balancing is the default load-balancing method, and is enabled by default at the global level. 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 addresses 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 mapping is dynamic when member links are added or deleted.
VLAN-Based Load Balancing
VLAN-based load balancing allows you to configure static assignment of user traffic, as identified by a VLAN ID, to a given member link of an EtherChannel. You can manually assign VLAN subinterfaces to a primary and secondary link. This feature allows load balancing to downstream equipment regardless of vendor equipment capabilities, and provides failover protection by redirecting traffic to the secondary member link if the primary link fails. Member links are supported with up to 16 bundles per chassis.
EtherChannels Load Balancing on the Transport Side of Cisco IOS XE Catalyst SD-WAN Devices
Minimum supported releases: Cisco IOS XE Catalyst SD-WAN Release 17.14.1a and Cisco Catalyst SD-WAN Manager Release 20.14.1.
Load balancing for EtherChannels on the transport side is achieved by using the inner IP headers, which include the original source and destination IP addresses found in encapsulated packets. Cisco IOS XE Catalyst SD-WAN devices use a hash algorithm to analyze the inner IP addresses for distribution of network traffic across available paths.
Configure load balancing for EtherChannels on the transport side using the port-channel load-balance-hash-algo sdwan command. With load balancing configured, a router distributes network traffic among all available paths within the EtherChannel. By default, sdwan uses the inner packet source and destination IP address.
Information About Configuring EtherChannels using Configuration Groups
Minimum supported releases: Cisco IOS XE Catalyst SD-WAN Release 17.15.1a and Cisco Catalyst SD-WAN Manager Release 20.15.1
You can configure port channel interfaces and member links using configuration groups in Cisco SD-WAN Manager.
Load Balancing on the Transport Side for Individual Port Channels
Minimum supported releases: Cisco IOS XE Catalyst SD-WAN Release 17.15.1a and Cisco Catalyst SD-WAN Manager Release 20.15.1
You can enable load balancing on per port channel in the interface using the load-balance-hash-algo sdwan command.