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Thursday, June 01, 2006

Configure EtherChannel trunking and VLAN tagging with Cisco 3560

The task: Configure a redundant networking setup between a NetApp filer and a Cisco switch running IOS.

The steps:
1. Pick 2 or more switch ports you would like to trunk together.
2. Configure the switch ports to use 802.1q standard:

conf t
interface gigabitEthernet 0/1
switchport trunk encapsulation dot1q
switchport mode trunk
channel-group 1 mode on
no ip address

3. Make sure that the channel-group mode is set to on and not desired which is the default.
4. Configure the filer to use a multi vif, and then configure VLAN tagged interfaces on top of the vif:

Note: In this example VLAN id 101 is used.
From /etc/rc:

vif create multi vif0 e4a e5a
vlan create -g vif0 101
ifconfig vif0-101 ... ...

Dr. Toaster Recommends:

  • Avoid using VLAN id 1 - The filer expects tagging of all Ethernet frames, yet some switches are configured to not tag VLAN id 1.

  • Naming conventions - I advise calling the trunks single0 and multi0 according to their type, and use names such as vif0 for any top-level trunk names.
    Some customers prefer to call the interfaces by their tasks, for example iscsi or exchange.


Eric (Geneva Switzerland) said...

thank you for the post.
What do you use / advise for the Linux side of EtherChannel trunking? have you faced any issue / pitfall with it.
best regards,

Eyal Traitel said...

Ethernet Bonding is the term that Linux distributions typically use.
You can find a good explanation to configure bonding in RedHat right here:


Dr. Toaster.

Anonymous said...

Thank you for the post.

Please note that there is a mistake in the netapp create vlan command :

After the -g option you need a keyword on/off

best regards

Jean-Claude Barbet (France)

Malcolm said...

It is probably possible to get around the problem of VLAN 1 being untagged by changing the native VLAN of the trunk on the Cisco side to an unused VLAN(you would have to do the port-channel members and then the port-channel should inherit it once created.


interface gi0/1
switchport vlan native 999
interface gi0/2
switchport vlan native 999

Then create the port-channel and hey presto! VLAN 1 packets will be tagged :)