Cisco Systems A9014CFD manual EtherChannel Configuration Guidelines and Restrictions

Chapter 9 Configuring EtherChannels

EtherChannel Configuration Guidelines and Restrictions

On ports configured to use LACP, LACP tries to configure the maximum number of compatible ports in an EtherChannel, up to the maximum allowed by the hardware (eight ports). If LACP cannot aggregate all the ports that are compatible (for example, the remote system might have more restrictive hardware limitations), then all the ports that cannot be actively included in the channel are put in hot standby state and are used only if one of the channeled ports fails. You can configure an additional 8 standby ports (total of 16 ports associated with the EtherChannel).

Understanding Port-Channel Interfaces

Each EtherChannel has a numbered port-channel interface. The configuration that you apply to the port-channel interface affects all LAN ports assigned to the port-channel interface.

After you configure an EtherChannel, the configuration that you apply to the port-channel interface affects the EtherChannel; the configuration that you apply to the LAN ports affects only the LAN port to which you apply the configuration. To change the parameters of all ports in an EtherChannel, apply the configuration commands to the port-channel interface, for example, Spanning Tree Protocol (STP) commands or commands to configure a Layer 2 EtherChannel as a trunk.

Understanding Load Balancing

An EtherChannel balances the traffic load across the links in an EtherChannel by reducing part of the binary pattern formed from the addresses in the frame to a numerical value that selects one of the links in the channel.

EtherChannel load balancing can use MAC addresses or IP addresses. EtherChannel load balancing can use either source or destination or both source and destination addresses or ports. The selected mode applies to all EtherChannels configured on the router. EtherChannel load balancing can use MPLS Layer 2 information.

Use the option that provides the balance criteria with the greatest variety in your configuration. For example, if the traffic on an EtherChannel is going only to a single MAC address and you use the destination MAC address as the basis of EtherChannel load balancing, the EtherChannel always chooses the same link in the EtherChannel; using source addresses or IP addresses might result in better load balancing.

EtherChannel Configuration Guidelines and Restrictions

Note When EtherChannel interfaces are configured improperly, they are disabled automatically to avoid network loops and other problems.

•The commands in this chapter can be used on all LAN ports in the Cisco ASR 901.

•Configure all LAN ports in an EtherChannel to use the same EtherChannel protocol; you cannot run two EtherChannel protocols in one EtherChannel.

•Configure all LAN ports in an EtherChannel to operate at the same speed and in the same duplex mode.

•LACP does not support half-duplex. Half-duplex ports in an LACP EtherChannel are put in the suspended state.

Cisco ASR 901 Series Aggregation Services Router Software Configuration Guide

9-4 OL-23826-09