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Configuring EtherChannel

Configuring EtherChannel

This chapter describes how to configure EtherChannel for Server Load Balancing (SLB) switches. For further information about the commands used in this chapter, refer to the command reference publications in the Cisco IOS documentation set and to "Command Reference."

This chapter includes the following sections.

Note   You are at Step 8 in the suggested process for configuring your SLB switch. See the "Configuring Your SLB Switch" section.

About EtherChannel

This section describes how to configure Fast EtherChannel or Gigabit EtherChannel in SLB or Layer 3 switching. EtherChannel is a trunking technology that groups together multiple full-duplex 802.3 Ethernet interfaces to provide fault-tolerant high-speed links between switches, routers, and servers. EtherChannel is a logical aggregation of multiple Ethernet interfaces. EtherChannel forms a single higher bandwidth routing or bridging endpoint. EtherChannel is designed primarily for host-to-switch connectivity or Inter-Switch Link (ISL) switch-to-switch connectivity (for example, connectivity to a Catalyst 5500 switch).

In summary, EtherChannel provides the following benefits:

The EtherChannel interface (consisting of up to four Fast Ethernet interfaces) is treated as a single interface, which is called a port channel. You must configure EtherChannel on the EtherChannel interface rather than on the individual member Ethernet interfaces. You create the EtherChannel interface by using the interface port-channel interface configuration command. The SLB switch supports up to 10 FEC port channels and 1 GEC port channel.

EtherChannel connections are fully compatible with Cisco IOS VLAN and routing technologies. The ISL VLAN trunking protocol can carry multiple VLANs across an EtherChannel, and routers attached to EtherChannel links can provide full multiprotocol routing with support for host standby using Hot Standby Router Protocol (HSRP).

The Catalyst 4840G SLB switch supports Fast EtherChannel (FEC) and Gigabit EtherChannel (GEC).

Cisco Fast EtherChannel technology builds upon standards-based 802.3 full-duplex Fast Ethernet to provide a reliable high-speed solution for the campus network backbone. Fast EtherChannel provides bandwidth scalability within the campus by providing increments of 200 Mbps to 400 Mbps.

Cisco Gigabit EtherChannel technology provides bandwidth scalability within the campus by providing increments of 2 Gbps to 4 Gbps.

Configuring the EtherChannel

Configuring a Fast EtherChannel or a Gigabit EtherChannel consists of the following process:

Step 1   Create an EtherChannel interface (port channel) and assign a network IP address.

Step 2   Assign the Fast Ethernet or Gigabit Ethernet interfaces (up to four) to the port channel.

Note   When assigning interfaces to a specific port channel, the interfaces must be all Fast Ethernet or all Gigabit Ethernet. You cannot mix interface types within a single port channel.

To create an EtherChannel interface and assign its IP address and subnet mask, perform the following steps:

Command Purpose

Step 1  

SLB-Switch(config)# interface port-channel 
channel-number

SLB-Switch(config-if)#

Creates the EtherChannel interface. The channel number can be from 1 to 64 for FEC and GEC.

Step 2  

SLB-Switch(config-if)# ip address 
ip-address subnet-mask

Assigns an IP address and subnet mask to the EtherChannel interface.

Step 3  

SLB-Switch(config-if)# exit

Exits interface configuration mode. Optionally, you can remain in interface configuration mode and enable other supported interface commands to meet your requirements.

To assign Ethernet interfaces to the EtherChannel, perform the following steps:

Caution The EtherChannel interface is the routed interface. Do not enable Layer 3 addresses on the physical Fast Ethernet or Gigabit Ethernet interfaces. Do not assign bridge groups on the physical Fast Ethernet or Gigabit Ethernet interfaces because doing so creates loops. Finally, you must disable the Spanning-Tree Protocol.

Command Purpose

Step 1  

SLB-Switch(config)# interface fastethernet 
interface_number

or
SLB-Switch(config)# interface 
gigabitethernet interface_number

SLB-Switch(config-if)#

Enters Ethernet interface configuration mode to configure the Fast Ethernet or Gigabit Ethernet interface you want to assign to the EtherChannel. You can assign any interface on any interface module installed on the system to the EtherChannel.

Step 2  

SLB-Switch(config-if)# no ip address

Disables the IP address. If the Fast Ethernet or Gigabit Ethernet interface already exists and has an IP address assigned, you must disable it before performing the next step.

The Ethernet interface uses the IP address assigned to the EtherChannel interface.

Step 3  

SLB-Switch(config-if)# channel-group 
channel-number

Assigns the Fast Ethernet or Gigabit Ethernet interfaces to the EtherChannel. The channel number must be the same channel number you assigned to the EtherChannel interface.

Step 4  

SLB-Switch(config-if)# exit

SLB-Switch#

Exits interface configuration mode. Repeat Steps 3 through 5 to add up to ten Fast Ethernet interfaces or a Gigabit Ethernet interface to the Fast EtherChannel.

Step 5  

SLB-Switch# copy system:running-config 
nvram:startup-config

Saves your configuration changes to NVRAM.

For a complete configuration example of Gigabit EtherChannel, see the "Example of an SLB and Layer 3 Switch with ISL, VLAN, and BVI with GEC" section.

Removing EtherChannel Interfaces

Removing an interface from the EtherChannel requires the following steps:

Step 1   Remove the network address from the interface.

Step 2   Remove the Ethernet interface(s) assigned to the EtherChannel.

To remove the network address from the EtherChannel, perform the following steps, beginning in global configuration mode:

Command Purpose

Step 1  

SLB-Switch(config)# interface port-channel 
channel-number

SLB-Switch(config-if)#

Enters interface configuration mode for the port channel.

Step 2  

SLB-Switch(config-if)# no ip address 
ip-address subnet-mask

Removes the IP address and subnet mask from the EtherChannel interface.

Step 3  

SLB-Switch(config-if)# exit

SLB-Switch(config)#

Exits interface configuration mode.

To remove Ethernet interfaces assigned to the EtherChannel, use the following steps, beginning in global configuration mode:

Command Purpose

Step 1  

SLB-Switch(config)# interface fastethernet 
interface_number

or
SLB-Switch(config)# interface 
gigabitethernet interface_number

SLB-Switch(config-if)#

Enters Ethernet interface configuration mode to configure the Fast Ethernet or Gigabit Ethernet interface in the EtherChannel.

Step 2  

SLB-Switch(config-if)# no channel-group 
channel-number

Removes the Ethernet interface assigned to the EtherChannel. The channel number must be the same channel number you assigned from the EtherChannel interface.

Step 3  

SLB-Switch(config-if)# end

SLB-Switch#

Exits interface configuration mode. Repeat Steps 1 through 3 to remove any other interfaces from the EtherChannel.

Step 4  

SLB-Switch# copy system:running-config 
nvram:startup-config

Saves your configuration changes to NVRAM.

The Cisco IOS software automatically removes a Fast Ethernet or Gigabit Ethernet interface from the EtherChannel if the interface goes down, and the software automatically adds the interface to the EtherChannel when the interface is back up.

Currently, EtherChannel relies on keepalives to detect whether the line protocol is up or down. Keepalives are enabled by default on the Fast Ethernet and Gigabit Ethernet interfaces. If the line protocol on the interface goes down because it did not receive a keepalive signal, the EtherChannel detects that the line protocol is down and removes the interface from the EtherChannel.

However, if the line protocol remains up because keepalives are disabled on the Fast Ethernet or Gigabit Ethernet interface, the EtherChannel cannot detect this link failure (other than a cable disconnect) and does not remove the interface from the EtherChannel even if the line protocol goes down. This can result in unpredictable behavior.

About Encapsulation over EtherChannel

When configuring encapsulation over FEC or GEC, be sure to configure the ISL or 802.1Q over the EtherChannel (that is, the port channel interface), not its member ports. Also make sure that you do not apply protocol-level configuration (such as an IP address or a bridge group assignment) to the member interfaces. All protocol-level configuration should be on the port channel or on its subinterface. You must configure ISL or 802.1Q encapsulation on the partner system of the EtherChannel as well.

Note   When configuring encapsulation on EtherChannel, you cannot configure both ISL and 802.1Q on the same EtherChannel interface.

Configuring Encapsulation over EtherChannel

To configure encapsulation on a subinterface over EtherChannel, perform the following steps:

Command Purpose

Step 1  

SLB-Switch(config)# interface port-channel 
channel-number

SLB-Switch(config-if)#

Creates the EtherChannel (or port channel) virtual interface. The channel number can be from 1 to 64 for FEC and GEC.

Step 2  

SLB-Switch(config-if)# exit

Returns to global configuration mode.

Step 3  

SLB-Switch(config)# interface fastethernet 
interface_number

or 
SLB-Switch(config)# interface 
gigabitethernet interface_number

SLB-Switch(config-if)#

Configures the port channel member.

Step 4  

SLB-Switch(config-if)# channel-group 
channel-number

Adds this interface to the EtherChannel. Up to four interfaces can be added.

Step 5  

SLB-Switch(config-if)# interface 
port-channel 
channel-number.subinterface-number

Configures the subinterface on the port channel.

Step 6  

SLB-Switch(config-if)# encapsulation isl 
vlan-id

Assigns the ISL encapsulation and VLAN ID to the subinterface.

Step 7  

SLB-Switch(config-if)# ip address 
ip-address subnet-mask

Assigns the protocol IP address and subnet mask to the subinterface.

Step 8  

SLB-Switch(config-if)# end

SLB-Switch#

Returns to privileged EXEC mode. Optionally, you can remain in interface configuration mode and enable other supported interface commands to meet your requirements.

Step 9  

SLB-Switch# copy system:running-config 
nvram:startup-config

Saves your configuration changes to NVRAM.

The following example demonstrates configuring a subinterface and encapsulation over an EtherChannel:

SLB-Switch(config)# interface port-channel 3

SLB-Switch(config-if)# exit

SLB-Switch(config-if)# interface fastethernet 3

SLB-Switch(config-if)# channel-group 3

SLB-Switch(config-if)# interface port-channel 3.3

SLB-Switch(config-subif)# encapsulation isl 11

SLB-Switch(config-subif)# ip address 10.3.4.5 255.0.0.0

SLB-Switch(config-subif)# end

SLB-Switch# copy system:running-config nvram:startup-config

Monitoring the EtherChannel

Once Fast EtherChannel or Gigabit EtherChannel is configured, you can monitor its status using the show interfaces port-channel command.

Configuring the EtherChannel concludes the suggested process for configuring your SLB switch. You have the option of configuring system management tasks to monitor and fine tune your SLB switch performance. For these tasks, refer to the Cisco IOS documentation set.


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Posted: Thu Sep 28 15:23:22 PDT 2000
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