after configuration. The next example shows how to
verify the configuration of port-channel interface 1 after the
interfaces have been configured. Switch#show etherchannel 1
port-channel
Channel-group listing:
----------------------
Group: 1
------------
Port-channels in the group:
----------------------
Port-channel: Po1
------------
Age of the
Port-channel = 01h:56m:20s
Logical slot/port = 10/1 Number
of ports = 2
GC = 0x00010001 HotStandBy port = null
Port state = Port-channel L3-Ag Ag-Inuse
Ports in the
Port-channel:
Index Load Port
-------------------
1 00 Fa5/6
0 00 Fa5/7
Time
since last port bundled: 00h:23m:33s Fa5/6 This example shows
how to verify the configuration of port-channel interface 1 (a
Layer 2 EtherChannel) after the interfaces have been
configured. Switch#show etherchannel 1 port-channel
Port-channels in the group:
----------------------
Port-channel: Po1
------------
Age of the Port-channel =
00h:23m:33s
Logical slot/port = 10/2 Number of ports in
agport = 2
GC = 0x00020001 HotStandBy port = null
Port
state = Port-channel Ag-Inuse
Ports in the
Port-channel:
Index Load Port
-------------------
1 00 Fa5/6
0 00 Fa5/7
Time
since last port bundled: 00h:23m:33s Fa5/6 Follow these
guidelines and restrictions when configuring EtherChannel
interfaces: - EtherChannel support: All Ethernet
interfaces on all modules support EtherChannel (maximum of
eight interfaces), with no requirement that interfaces be
physically contiguous or on the same module.
- Speed
and duplex: Configure all interfaces in an EtherChannel to
operate at the same speed and in the same duplex mode. Also, if
one interface in the bundle is shut down, it is treated as a
link failure, and traffic traverses other links in the
bundle.
- Switched port analyzer (SPAN) and
EtherChannel: An EtherChannel will not form if one of the
interfaces is a SPAN destination port.
- Layer 3
EtherChannels: Assign Layer 3 addresses to the port-channel
logical interface, not to the physical interfaces in the
channel.
- VLAN match: All interfaces in the
EtherChannel bundle must be assigned to the same VLAN or be
configured as a trunk.
- Range of VLANs: An
EtherChannel supports the same allowed range of VLANs on all
the interfaces in a trunking Layer 2 EtherChannel. If the
allowed range of VLANs is not the same, the interfaces do not
form an EtherChannel, even when set to auto or
desirable mode. For Layer 2 EtherChannels, either assign
all interfaces in the EtherChannel to the same VLAN or
configure them as trunks.
- STP path cost:
Interfaces with different STP port path costs can form an
EtherChannel as long they are otherwise compatibly configured.
- Port channel versus interface configuration:
After you configure an EtherChannel, any configuration you
apply to the port-channel interface affects the EtherChannel.
Any configuration you apply to the physical interfaces affects
only the specific interface you configured.
The
example illustrated in Figure shows how to configure an
EtherChannel following the guidelines.
Content 3.4
Configuring Link Aggregation with EtherChannel
3.4.5 Configuring Load Balancing over EtherChannel
In Figure , an EtherChannel of four workstations communicates
with a router. Because the router is a single-MAC-address
device, source-based forwarding on the switch’s EtherChannel
ensures that the switch uses all available bandwidth to the
router. The router is configured for destination-based
forwarding, because the large number of workstations ensures
that the traffic is evenly distributed from the router
EtherChannel. Use the option that provides the greatest variety
in your configuration. For example, if the traffic on a channel
is going only to a single MAC address, using the destination
MAC address always chooses the same link in the channel; using
source addresses might result in better load balancing.
EtherChannel balances the traffic load across the links in a
channel 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
either source-MAC or destination-MAC address forwarding. With
source-MAC address forwarding, when packets are forwarded to an
EtherChannel, they are distributed across the ports in the
channel based on the source MAC address of the incoming packet.
Therefore, to provide load balancing, packets from different
hosts use different ports in the channel, but packets from the
same host use the same port in the channel (and the MAC address
learned by the switch does not change). With destination-MAC
address forwarding, when packets are forwarded to an
EtherChannel, they are distributed across the ports in the
channel based on the destination MAC address of the frame.
Therefore, packets to the same destination are forwarded over
the same port, and packets to a different destination are sent
on a different port in the channel. You configure the load
balancing and forwarding method by using the port-channel
load-balance global configuration command. EtherChannel
balances traffic load across the links in a channel. The
default and load balancing method varies among the Cisco
Catalyst models. Load balancing is applied globally for all
EtherChannel bundles in the switch. To configure EtherChannel
load balancing, use the port-channel load-balance
command. Load balancing can be based on the following
variables: - src-mac: Source MAC address
- dst-mac: Destination MAC address
-
src-dst-mac: Source and destination MAC addresses
- src-ip: Source IP address
- dst-ip:
Destination IP address
- src-dst-ip: Source and
destination IP addresses (default)
- src-port:
Source TCP/User Datagram Protocol (UDP) port
-
dst-port: Destination TCP/UDP port
-
src-dst-port: Source and destination TCP/UDP ports
This example shows an example of how to configure and
verify EtherChannel load balancing. Switch(config)#
port-channel load-balance src-dst-ip
Switch(config)#
exit
Switch# show etherchannel load-balance
Source XOR Destination IP address
Content
3.5 Spanning Tree Lab Exercises
3.5.1 Lab 3-1 Spanning Tree Protocol (STP) Default
Behavior Lab Activity Lab Exercise: Lab 3-1
Spanning Tree Protocol (STP) Default Behavior The purpose of
this lab is to observe the default behavior of STP.
Content 3.5 Spanning Tree Lab Exercises
3.5.2 Lab 3-2 Modifying Default Spanning Tree
Behavior Lab Activity Lab Exercise: Lab 3-2
Modifying Default Spanning Tree Behavior The purpose of this
lab is to observe what happens when the default spanning tree
behavior is modified.
Content 3.5
Spanning Tree Lab Exercises 3.5.3 Lab 3-3
Per-VLAN Spanning Tree Behavior Lab Activity Lab
Exercise: Lab 3-3 Per-VLAN Spanning Tree Behavior The purpose
of this lab is to observe what happens when there is a separate
spanning tree instance per VLAN. This lab also looks at
changing spanning tree mode to rapid spanning tree.
Content 3.5 Spanning Tree Lab Exercises
3.5.4 Lab 3-4 Multiple Spanning Tree Lab
Activity Lab Exercise: Lab 3-4 Multiple Spanning Tree The
purpose of this lab is to observe the behavior of MST (multiple
spanning tree).
Content 3.5 Spanning
Tree Lab Exercises 3.5.5 Lab 3-5 Configuring
Etherchannel Lab Activity Lab Exercise: Lab 3-5
Configuring Etherchannel The purpose of this lab is to
configure and observe Etherchannel.
Content