Configure EtherChannel on Catalyst Switches
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Introduction
This document explains how to configure EtherChannel between Cisco
Catalyst switches. This document is applicable to Catalyst 4500, 3750, 3560 and
3550 series switches.
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Components
To perform the steps described in this document, you need to have this
equipment:
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EtherChannel Overview
EtherChannel provides fault-tolerant high-speed links between switches,
routers, and servers. EtherChannel provides automatic recovery for the loss of
a link by redistributing the load across the remaining links. If a link fails,
EtherChannel redirects traffic from the failed link to the remaining links in
the channel without intervention. All ports participating in EtherChannel must
have the same configuration for speed and duplex settings. All ports in each
EtherChannel must be configured as either Layer 2 or Layer 3 ports.
Each EtherChannel has a port-channel logical interface number assigned
to it. This port-channel interface number corresponds to the one specified with
the channel-group interface configuration command. After you configure an
EtherChannel, configuration changes applied to the port-channel interface apply
to all the physical ports assigned to the port-channel interface.
EtherChannels can be automatically configured with either Port
Aggregation Protocol (PAgP) or Link Aggregation Control Protocol (LACP). PAgP
is a Cisco-proprietary protocol that can only run on Cisco switches, and on
those switches that licensed vendor’s license to support PAgP. LACP (IEEE
802.3ad) allows Cisco switches to manage EtherChannels between switches that
conform to the 802.3ad protocol. You can configure a PAgP EtherChannel with up
to eight Ethernet ports of the same type. You can configure a LACP EtherChannel
with up to 16 Ethernet ports of the same type. Up to eight ports can be active,
and up to eight ports can be in standby mode. PAgP works in these
modes:
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Auto: Places a port into a passive negotiating
state, in which the port responds to PAgP packets it receives but, does not
start PAgP packet negotiation. This setting minimizes the transmission of PAgP
packets.
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Desirable: Places a port into an active
negotiating state, in which the port starts negotiations with other ports by
sending PAgP packets.
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On: Forces a port to channel without PAgP (or
LACP). In the On mode, a usable EtherChannel exists only when a port group in
the On mode is connected to another port group in the On
mode.
LACP works in these modes:
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Active: Places a port into an active negotiating
state in which the port starts negotiations with other ports by sending LACP
packets.
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Passive: Places a port into a passive negotiating
state in which the port responds to LACP packets that it receives, but does not
start LACP packet negotiation. This setting minimizes the transmission of LACP
packets.
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On: Forces a port to channel without PAgP (or
LACP). In the On mode, a usable EtherChannel exists only when a port group in
the On mode is connected to another port group in the On
mode.
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Connect to the Switch
Follow these steps to connect your PC to the switch for
configuration:
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Connect a PC to the switch with a console
cable.
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Create a HyperTerminal connection to your switch. For more
information, refer to
Create a
HyperTerminal Connection.
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Log into the switch with the login, and password that you entered
in fields B10 and B11 of the Switch Worksheet.
Username:admin
Password:
Note: If you do not know the password for your switch, refer to
Manually
Reset the Password on a Catalyst Switch.
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Type enable, and press Enter to
access the privileged mode. Type the enable password that you entered in field
S5 of the Switch Port Assignment Worksheet.
switch>enable
Password:
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Configure EtherChannel on Catalyst switch
To Configure Layer 2 EtherChannels, follow these:
Configure Layer 2 EtherChannels
Follow these steps to Configure Layer 2 EtherChannels:
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Enter the configure terminal command to enter
global configuration mode. Get in to the desired interface which is to be
configured for EtherChannel by entering interface command
followed by interface id or enter a range of interfaces.
Switch#configure terminal
Switch(config)#interface range fastethernet 0/1 -2
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Enter the switchport mode access command to make
this interface a layer 2 interface. Enter the switchport access vlan
command followed by a vlan id to make the port member of vlan of your
choice. All ports in a EtherChannel must be member of same vlan.
Switch(config-if-range)#switchport mode access
Switch(config-if-range)#switchport access vlan 10
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Enter the channel group command followed by a
group id, and mode to make this interface a member of the channel group.
Switch(config-if-range)#channel-group 10 mode desirable
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Exit from configuration mode by entering end
command, and save this configuration to flash with copy running-config
startup-config command.
Switch(config-if-range)#end
Switch#copy running-config startup-config
Repeat the same steps on the other end switch. You can also
configure more Layer 2 EtherChannels on the same switch with the above
mentioned steps.
Configure Layer 3 EtherChannels
Follow these steps to Configure Layer 3 Ether
Channels:
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Enter the configure terminal command to enter
global configuration mode. Use the interface port-channel global
configuration command to manually create the port-channel logical
interface.
Switch#configure terminal
Switch(config)#interface port-channel 10
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Enter the no switchport command to put the
interface into Layer 3 mode. Assign an IP address, and subnet mask to the
EtherChannel by entering ip address command followed by an ip
address and subnet mask.
Switch(config-if)#no switchport
Switch(config-if)#ip address 192.168.12.10 255.255.255.0
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Get in to the desired interface which is to be configured for
EtherChannel by entering interface command followed by
interface id or enter a range of interfaces.
Switch(config-if)#interface range fastethernet 0/1 -2
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Enter the no ip address command to ensure that
there is no IP address assigned to the physical port. Enter the no
switchport command to put the interface into Layer 3 mode.
Switch(config-if-range)#no ip address
Switch(config-if-range)#no switchport
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Enter the channel group command followed by a
group id, and mode to make this interface a member of the channel group.
Switch(config-if-range)#channel-group 10 mode desirable
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Exit from configuration mode by entering end
command, and save this configuration to flash with the copy
running-config startup-config command.
Switch(config-if-range)#end
Switch#copy running-config startup-config
Repeat the same steps on the other end switch. You can also
configure more Layer 3 EtherChannels on the same switch using the above
mentioned steps.
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Verify your configuration
Enter the show interfaces port-channel command
followed by the channel group number, and check the output to see if the port
channel is up.
Switch#show interface port-channel 10
Port-channel10 is up, line protocol is up
Hardware is EtherChannel, address is 0002.4b28.db02 (bia 0002.4b28.db02)
MTU 1500 bytes, BW 200000 Kbit, DLY 1000 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Full-duplex, 100Mb/s
input flow-control is off, output flow-control is off
Members in this channel: Fa0/1 Fa0/2
!! Output suppressed
You can also use the show etherchannel channel-group-number
summary command to check the status of EtherChannel. This is the
output for L2 EtherChannel.
Switch#show etherchannel 10 summary
Flags: D - down P - in port-channel
I - stand-alone s - suspended
H - Hot-standby (LACP only)
R - Layer3 S - Layer2
U - in use f - failed to allocate aggregator
u - unsuitable for bundling
w - waiting to be aggregated
d - default port
Number of channel-groups in use: 1
Number of aggregators: 1
Group Port-channel Protocol Ports
------+-------------+-----------+------------------------------------------
10 Po10(SU) PAgP Fa0/1(P) Fa0/2(P)
This is the output for L3 EtherChannel:
Switch#show etherchannel 10 summary
Flags: D - down P - in port-channel
I - stand-alone s - suspended
H - Hot-standby (LACP only)
R - Layer3 S - Layer2
U - in use f - failed to allocate aggregator
u - unsuitable for bundling
w - waiting to be aggregated
d - default port
Number of channel-groups in use: 2
Number of aggregators: 2
Group Port-channel Protocol Ports
------+-------------+-----------+-------------------------------
10 Po10(RU) PAgP Fa0/1(P) Fa0/2(P)
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Next Step
You have completed configuring EtherChannel on your Cisco Catalyst
Switch.
To make further changes to your switch, refer to
Switch
Support Page.
To configure other devices in your network, refer to
Configuration
Overview Page.
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Troubleshoot the Procedure
This section provides information about common problems that you may
encounter. If this information does not solve your problem, contact the
SMB
Technical Assistance Center (SMB TAC) for assistance.
Problem
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Cause(s) and Suggested Solution(s)
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The switch boots and displays several error messages but does
not display a prompt in HyperTerminal.
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Press Enter to clear the output and display
the switch prompt.
For further assistance, contact the
SMB
Technical Assistance Center (SMB TAC).
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