Configuring EtherChannel and VLAN Trunks

Table Of Contents

Configuring EtherChannel and VLAN Trunks

Configure EtherChannel

Configure VLAN Trunks

Configuring EtherChannel and VLAN Trunks

EtherChannel port bundles allow you to increase the bandwidth of connections between devices by grouping multiple physical ports into a single virtual port.

VLAN trunks are point-to-point links that carry the traffic of multiple VLANs. Trunk ports are useful in the network backbone, where traffic from many VLANs is handled.

You can configure EtherChannel links as VLAN trunks, providing high-bandwidth connections to the network backbone.

To configure EtherChannel VLAN trunks on the switch, perform these tasks:

Step 1 Configure EtherChannel—Configure multiple ports between switches as a single virtual link.

Step 2 Configure VLAN Trunks—Configure the EtherChannel link as a trunk port to transport traffic for multiple VLANs.

Configure EtherChannel

EtherChannel port bundles provide increased bandwidth between network devices by grouping multiple Fast or Gigabit Ethernet ports into a single logical transmission path.

An EtherChannel bundle contains two or more Fast or Gigabit EtherChannel-capable ports. EtherChannel capabilities and flexibility vary depending on your hardware and software. Use the show port capabilities command to determine the supported channeling capabilities on your switch.

The Port Aggregation Protocol (PAgP) negotiates EtherChannel port groups automatically. By default, Ethernet ports are set to auto. If a group of EtherChannel ports set to auto is connected to a group of ports set to desirable or on, PAgP automatically creates an EtherChannel connection between those ports. For complete information on the various EtherChannel modes, refer to the Software Configuration Guide.

You can configure ports to negotiate an EtherChannel bundle with the neighboring device automatically (using the auto and desirable modes), or you can place the ports in on mode on both ends of the link. Ports in on mode will not form a channel with ports in auto or desirable mode. By default, Fast and Gigabit Ethernet ports are in auto mode.

Note There are additional configuration restrictions associated with EtherChannel port bundles. For complete information, refer to the Software Configuration Guide for your switch.

To configure a group of Fast Ethernet or Gigabit Ethernet ports as an EtherChannel port bundle, perform this task in privileged mode:

Task

Command

Step 1

If you are unsure which ports support EtherChannel or how the ports are grouped, verify the port groups for the module or switch you are configuring.

show port capabilities [mod_num[/port_num]]

Step 2

Create a channel on the desired ports.

set port channel port_list mode {on | off | desirable | auto} [silent | non-silent]

Step 3

Verify the channeling configuration.

show port channel [mod_num[/port_num]]

This example shows how to configure a two-port Gigabit EtherChannel bundle and how to verify the EtherChannel configuration (this example assumes that there are no configuration mismatches between the local and neighboring ports, and that the ports on the other end of the link are in auto or desirable mode):

Console> (enable) set port channel 2/1-2 mode desirable
Port(s) 2/1-2 are assigned to admin group 21.
Port(s) 2/1-2 channel mode set to desirable.
Console> (enable) show port channel
Port Status Channel Admin Ch
Mode Group Id
----- ---------- -------------------- ----- -----
2/1 connected desirable silent 21 833
2/2 connected desirable silent 21 833
----- ---------- -------------------- ----- -----

Port Device-ID Port-ID Platform
----- ------------------------------- ------------------------- ----------------
2/1 003812064 1/1 WS-C5509
2/2 003812064 1/2 WS-C5509
----- ------------------------------- ------------------------- ----------------
Console> (enable)

Configure VLAN Trunks

VLAN trunks carry the traffic of multiple VLANs. Fast Ethernet and Gigabit Ethernet ports (including EtherChannel port bundles) can use Inter-Switch Link (ISL) or IEEE 802.1Q encapsulation for VLAN trunking. Other media use other encapsulation schemes (for example, LAN Emulation on ATM).

By default, Fast Ethernet and Gigabit Ethernet ports are in auto mode. If the port on the other end of the link is in desirable mode or on, a port in auto mode automatically becomes a trunk port.

The default trunk encapsulation depends on which encapsulation the hardware supports:

•negotiate (on hardware supporting both ISL and 802.1Q)

•isl (on hardware supporting ISL only)

•dot1q (on hardware supporting 802.1Q only)

Note For complete information on the various trunk modes and encapsulation types, refer to the Software Configuration Guide for your switch.

To configure a Fast Ethernet or Gigabit Ethernet port as a trunk, perform this task in privileged mode:

Task

Command

Step 1

If you are unsure which encapsulation types a port supports, verify the port capabilities.

show port capabilities [mod_num[/port_num]]

Step 2

Configure a Fast or a Gigabit Ethernet port as a trunk. If you are configuring an EtherChannel port bundle as a trunk, specify any one of the ports in the channel.

set trunk mod_num/port_num {on | desirable | auto} {isl | dot1q | negotiate}

Step 3

Verify that the trunk configuration is correct.

show trunk

This example shows how to configure a port to become a trunk and how to verify the trunk configuration (this example assumes that the port on the other end of the link is in auto, desirable, or on mode and supports IEEE 802.1Q encapsulation):

Console> (enable) set trunk 2/1 desirable dot1q
Port(s) 2/1-2 trunk mode set to desirable.
Port(s) 2/1-2 trunk type set to dot1q.
Console> (enable) show trunk
Port Mode Encapsulation Status Native vlan
-------- ----------- ------------- ------------ -----------
2/1 desirable dot1q trunking 1
2/2 desirable dot1q trunking 1

Port Vlans allowed on trunk
-------- ---------------------------------------------------------------------
2/1 1-1005
2/2 1-1005

Port Vlans allowed and active in management domain
-------- ---------------------------------------------------------------------
2/1 1,10,20,30,40,50,60
2/2 1,10,20,30,40,50,60

Port Vlans in spanning tree forwarding state and not pruned
-------- ---------------------------------------------------------------------
2/1 1,10,20,30,40,50,60
2/2 1,10,20,30,40,50,60
Console> (enable)

	Task	Command
Step 1	If you are unsure which ports support EtherChannel or how the ports are grouped, verify the port groups for the module or switch you are configuring.	show port capabilities [mod_num[/port_num]]
Step 2	Create a channel on the desired ports.	set port channel port_list mode {on \| off \| desirable \| auto} [silent \| non-silent]
Step 3	Verify the channeling configuration.	show port channel [mod_num[/port_num]]

	Task	Command
Step 1	If you are unsure which encapsulation types a port supports, verify the port capabilities.	show port capabilities [mod_num[/port_num]]
Step 2	Configure a Fast or a Gigabit Ethernet port as a trunk. If you are configuring an EtherChannel port bundle as a trunk, specify any one of the ports in the channel.	set trunk mod_num/port_num {on \| desirable \| auto} {isl \| dot1q \| negotiate}
Step 3	Verify that the trunk configuration is correct.	show trunk