Understanding Port Channel Interfaces; Understanding Load Balancing; Etherchannel Feature Configuration Guidelines And Restrictions - Cisco 7609 Configuration Manual

Chapter 13 Configuring EtherChannels

Understanding Port Channel Interfaces

Each EtherChannel has a numbered port channel interface. Release 12.1(5)E and later releases support
a maximum of 64 port channel interfaces, numbered from 1 to 256.
Note Releases 12.1(4)E1, 12.1(3a)E4, and 12.1(3a)E3 support a maximum of 64 port channel interfaces,
numbered from 1 to 64. Releases 12.1(2)E and earlier support a maximum of 256 port channel interfaces,
numbered from 1 to 256.
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
where 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. With a PFC2, EtherChannel load
balancing can also use Layer 4 port numbers. 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.
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 Feature Configuration Guidelines and Restrictions

When EtherChannel interfaces are configured improperly, they are disabled automatically to avoid
network loops and other problems. To avoid configuration problems, observe these guidelines and
restrictions:
•
•
•
•
78-14064-04
All Ethernet LAN ports on all modules, including those on a redundant supervisor engine, support
EtherChannels (maximum of eight LAN ports) with no requirement that the LAN ports be physically
contiguous or on the same module.
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.
EtherChannel Feature Configuration Guidelines and Restrictions
Cisco 7600 Series Router Cisco IOS Software Configuration Guide—12.1E
13-5