Cisco WS-C3560E-48PD-SF Command Reference - Page 63

Chapter 2 Catalyst 3560 Switch Cisco IOS Commands channel-group Defaults No channel groups are assigned. No mode is configured. Command Modes Interface configuration Command History Release 12.1(19)EA1 12.2(25)SE Modification This command was introduced. The channel-group-number range was changed from 1 to 12 to 1 to 48. Usage Guidelines For Layer 2 EtherChannels, you do not have to create a port-channel interface first by using the interface port-channel global configuration command before assigning a physical port to a channel group. Instead, you can use the channel-group interface configuration command. It automatically creates the port-channel interface when the channel group gets its first physical port if the logical interface is not already created. If you create the port-channel interface first, the channel-group-number can be the same as the port-channel-number, or you can use a new number. If you use a new number, the channel-group command dynamically creates a new port channel. You do not have to disable the IP address that is assigned to a physical port that is part of a channel group, but we strongly recommend that you do so. You create Layer 3 port channels by using the interface port-channel command followed by the no switchport interface configuration command. You should manually configure the port-channel logical interface before putting the interface into the channel group. After you configure an EtherChannel, configuration changes that you make on the port-channel interface apply to all the physical ports assigned to the port-channel interface. Configuration changes applied to the physical port affect only the port where you apply the configuration. To change the parameters of all ports in an EtherChannel, apply configuration commands to the port-channel interface, for example, spanning-tree commands or commands to configure a Layer 2 EtherChannel as a trunk. If you do not specify non-silent with the auto or desirable mode, silent is assumed. The silent mode is used when the switch is connected to a device that is not PAgP-capable and seldom, if ever, sends packets. A example of a silent partner is a file server or a packet analyzer that is not generating traffic. In this case, running PAgP on a physical port prevents that port from ever becoming operational. However, it allows PAgP to operate, to attach the port to a channel group, and to use the port for transmission. Both ends of the link cannot be set to silent. In the on mode, an EtherChannel exists only when a port group in the on mode is connected to another port group in the on mode. Caution You should use care when using the on mode. This is a manual configuration, and ports on both ends of the EtherChannel must have the same configuration. If the group is misconfigured, packet loss or spanning-tree loops can occur. Do not configure an EtherChannel in both the PAgP and LACP modes. EtherChannel groups running PAgP and LACP can coexist on the same switch. Individual EtherChannel groups can run either PAgP or LACP, but they cannot interoperate. 78-16405-05 Catalyst 3560 Switch Command Reference 2-31