EtherChannel Configurations

This chapter describes how to configure EtherChannel for switch routers. 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 6 in the suggested process for configuring your switch router (see Table 2-1). You should have already configured bridging and should now be ready to proceed with configuring the EtherChannel.

About EtherChannel

This section describes how to configure Fast EtherChannel or Gigabit EtherChannel in 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:

Logical aggregation of bandwidth
Load balancing
Fault tolerance

The EtherChannel interface (consisting of up to four 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 switch router supports up to 64 port channels.

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 Host Standby Router Protocol (HSRP).

The Catalyst 8500 campus switch router 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 800 Mbps.

Cisco Gigabit EtherChannel technology provides bandwidth scalability within the campus by providing increments of 2 Gbps to 8 Gbps.

Note IP/IPX filtering at Layer 3 with the ACL daughter card is not supported for EtherChannel.

Configuring the EtherChannel

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

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

Table 7-1 shows an example of creating an EtherChannel interface and assigning its IP address and subnet mask.

Table 7-1: Creating the EtherChannel Interface

Step Command Purpose

1
Router(config)# interface port-channel channel-number

From global configuration mode, create the EtherChannel interface. The channel number can be from 1 to 64 for FEC and GEC.

2
Router(config-if)# ip address ip-address subnet-mask

Assign an IP address and subnet mask to the Fast EtherChannel interface.

For IPX, use the ipx network network-number command.

3
Router(config-if)# exit

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

Step	Command	Purpose
1	Router(config)# interface port-channel channel-number	From global configuration mode, create the EtherChannel interface. The channel number can be from 1 to 64 for FEC and GEC.
2	Router(config-if)# ip address ip-address subnet-mask	Assign an IP address and subnet mask to the Fast EtherChannel interface. For IPX, use the ipx network network-number command.
3	Router(config-if)# exit	Exit this mode. Optionally, you can remain in interface configuration mode and enable other supported interface commands to meet your requirements.

Table 7-2 shows an example of assigning Ethernet interfaces to the EtherChannel.

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.

Table 7-2: Assigning Ethernet Interfaces to the EtherChannel

Step Command Purpose

1
Router(config)# interface fa x/0/z

or

Router(config)# interface gi x/0/z

Enter 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.

2
Router(config-if)# no ip address

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

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

3
Router(config-if)# channel-group channel-number

Assign 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.

4
Router(config-if)# exit

Exit interface configuration mode and repeat Steps 3 through 6 to add up to four Fast Ethernet or Gigabit Ethernet interfaces to the Fast EtherChannel.

5
Router# copy running-config startup-config

Save your configuration changes to NVRAM.

Step	Command	Purpose
1	Router(config)# interface fa x/0/z or Router(config)# interface gi x/0/z	Enter 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.
2	Router(config-if)# no ip address	If the Fast Ethernet or Gigabit Ethernet interface already exists and has an IP address assigned, you must disable the IP address before performing the next step. The Ethernet interface uses the IP address assigned to the EtherChannel interface.
3	Router(config-if)# channel-group channel-number	Assign 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.
4	Router(config-if)# exit	Exit interface configuration mode and repeat Steps 3 through 6 to add up to four Fast Ethernet or Gigabit Ethernet interfaces to the Fast EtherChannel.
5	Router# copy running-config startup-config	Save your configuration changes to NVRAM.

Table 7-3 shows an example of removing an interface from the EtherChannel.

Table 7-3: Removing an Interface from the EtherChannel

Step Command Purpose

1
Router(config)# interface port-channel channel-number

From global configuration mode, create the EtherChannel interface. The channel number can be from 1 to 64 for FEC and GEC.

2
Router(config-if)# ip address ip-address subnet-mask

Assign an IP address and subnet mask to the Fast EtherChannel interface.

For IPX, use the ipx network network-number command.

3
Router(config-if)# exit

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

Step	Command	Purpose
1	Router(config)# interface port-channel channel-number	From global configuration mode, create the EtherChannel interface. The channel number can be from 1 to 64 for FEC and GEC.
2	Router(config-if)# ip address ip-address subnet-mask	Assign an IP address and subnet mask to the Fast EtherChannel interface. For IPX, use the ipx network network-number command.
3	Router(config-if)# exit	Exit this mode. Optionally, you can remain in interface configuration mode and enable other supported interface commands to meet your requirements.

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

Table 7-4 shows an example of configuring encapsulation over EtherChannel.

Table 7-4: Configuring Encapsulation over EtherChannel

Step Command Purpose

1
Router(config)# interface port-channel channel-number

From global configuration mode, create the EtherChannel (or port channel) virtual interface. The channel number can be from 1 to 64 for FEC and GEC.

2
Router(config)# interface fa x/0/z

or

Router(config)# interface gi x/0/z

Configure the port-channel member.

3
Router(config-if)# channel-group channel-number

Up to four interfaces can be added to the EtherChannel.

4
Router(config)# interface port-channel channel-number.subinterface-number

Configure the subinterface on the port channel.

5
Router(config-if)# encap isl vlan-id

Assign the ISL encapsulation to the subinterface.

6
Router(config-if)# ip address ip-address subnet-mask

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

7
Router(config-if)# exit

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

8
Router# copy running-config startup-config

Save your configuration changes to NVRAM.

Step	Command	Purpose
1	Router(config)# interface port-channel channel-number	From global configuration mode, create the EtherChannel (or port channel) virtual interface. The channel number can be from 1 to 64 for FEC and GEC.
2	Router(config)# interface fa x/0/z or Router(config)# interface gi x/0/z	Configure the port-channel member.
3	Router(config-if)# channel-group channel-number	Up to four interfaces can be added to the EtherChannel.
4	Router(config)# interface port-channel channel-number.subinterface-number	Configure the subinterface on the port channel.
5	Router(config-if)# encap isl vlan-id	Assign the ISL encapsulation to the subinterface.
6	Router(config-if)# ip address ip-address subnet-mask	Assign the protocol IP address and subnet mask to the subinterface.
7	Router(config-if)# exit	Exit this mode. Optionally, you can remain in interface configuration mode and enable other supported interface commands to meet your requirements.
8	Router# copy running-config startup-config	Save your configuration changes to NVRAM.

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 switch router. You have the option of configuring system management tasks to monitor and fine tune your switch router's performance. For these tasks, refer to the Cisco IOS documentation set.

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