Ethernet Switches & Routers

Posts: 46
Registered: ‎11-01-2010


Me again!

I have to use Vlan 1 for legacy of my older configuration, I'm doing a transition to another vlan.

Problem is on my backbone I cannot seem to make pass the vlan 1 through the trunk.

I have 2 routers, the Brocade Backbone and a Cisco Catalyst L3 switch.

I have create VLAN 1 and 10. Vlan 10 is working fine and can be reached through my entire network.

Ports untagged for vlan 1 on my Backbone only can see each other and cannot go out of the backbone.

I do have a trunk between all my switchs that should let vlan 1 go throught as well as vlan 10.

Why on earth only vlan 1 can't get throught.

I also have changed the default-vlan to be vlan 444 .

Thanks again for your precious help. Be free to ask any question if you have any doubt on my configuration.

Posts: 52
Registered: ‎02-18-2010

Re: VLAN 1


Let me see if I understand your configuration: you have a Brocade switch that is connected to a Cisco Catalyst switch and you want to pass VLAN 1 and 10 between these two switches using a tagged interface, or to use Cisco terminology, a trunked interface. If this is correct, this should get you working.

On the Brocade switch, make sure VLAN 1 and 10 are tagged on the interface used to connect the two switches together. Then enter “dual-mode 1” on the port that is connecting the Brocade and Cisco switch together.

In the below example, interface Ethernet 1/1 is connecting the two switches together.

FastIron(config)#vlan 1

FastIron(config-vlan-1)#tagged e 1/1

FastIron(config-vlan-1)#vlan 10

FastIron(config-vlan-10)#tagged e1/1

FastIron(config-vlan-10)interface e 1/1

FastIron(config-if-e1000-1/1)#dual-mode 1

The "dual-mode" command will allow the Brocade device to pass both tagged and untagged traffic on the same interface. By default, the Cisco switch is expecting to see VLAN 1 untagged.

Please let me know if this takes care of your issue or if I did not understand your configuration.

Posts: 52
Registered: ‎02-18-2010

Re: VLAN 1

The dual-mode command is used to allow an interface to send and receive both tagged and untagged traffic. A very common example of its use is when you are supporting an environment using IP phones were the PC's are connecting to the switch port built into the phones. In this case, all traffic from the phone will be tagged in the voice vlan and all traffic from the PC will be untagged. So the switch has to be able to send and receive both tagged and untagged traffic. In this case, you will use the dual-mode command on all ports that will support a IP Phone.

Please post if you have any questions!


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