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Basic VLAN configuration in a multi-switch cluster..

ctmanagementinc
Level 1
Level 1

Hey guys, I have a question that I think is probably easy for you guys, but I'm not just seeing the solution.

I'm new to Cisco products and don't know my way around the CLI, but I am able to use the Cisco Network Assistant to get things done.  I'm trying to create a basic VLAN for (4) devices to ONLY be able to talk to each other.  3 of the devices are connected to the same Catalyst 3750X switch stack - I have the three ports in question configured as Static Access, VLAN number 50 - that configuration works fine, the 3 devices can talk to each other and no one else.  Device 4 is connected to another Catalyst 3750X switch stack at another physical location on my network.  These Catalyst switch stacks are 3 hops from each other:  Catalyst 3750X (stack A) > Catalyst 3750 (stack A) > Catalyst 3750 (stack B) > Catalyst 3750X (stack B).  Each switch stack is connected via fiber using the gigabit interfaces.  All of these swithes are in a cluster that was configured via the Cisco Network Assistant.

As mentioned, I've setup all the ports in question as Static Access, VLAN number 50.  This works fine between the devices on one physical switch, but the device that's connected to the other physical switch can't communicate on VLAN 50. 

What am I missing?  Since they are in a cluster, shouldn't this configuration work or do I still need some some of trunk port?

Thanks in advance for any assistance you guys can provide.

4 Replies 4

You need to have the Vlan 50 active on the path to the other switch.

3750X (stack A) > Catalyst 3750 (stack A) > Catalyst 3750 (stack B) > Catalyst 3750X (stack B)

Vlan 50                   Need vlan 50                   Need vlan 50                        Vlan 50         

So the simple solution will be toactivate vlan 50 on the other switches as well:

conf t

vlan database

vlan 50

end

And also make sure that on trunk you are not pruning this vlan.

Hope this helps.

danielkleeman
Level 1
Level 1

To clarify Mandlenkosi's response you will need a trunk between each stack correctly configured to carry VLAN 50 as well as other VLANs. It is possible that if you have only used VLAN 1 on all ports up to now that you do not have a trunk linking each switch.

You can set up a trunk in CNA. As Mandlenkosi says, I would be careful not to allow pruning.

Daniel

ctmanagementinc
Level 1
Level 1

Thank you both for your replies, I've got it working now!  What I ended up doing was change the VLAN Operating Mode of each fiber uplink between each hop to Dynamic Desired - once I did that, each link became an ISL trunk and the VLAN config was carried to each hop along the way, all the way to the end I was trying to reach.

Regarding pruning, what is the reasoning behind not allowing it?

Regarding pruning, what is the reasoning behind not allowing it?

I am not clear how many switches are in your chain, but the issue with pruning is that a if there is a switch in the middle of your chain that does not have or need the VLAN then pruning will allow VLAN 50 to be pruned (i.e. dropped) from the middle switch. Thus it will not make it to where you need it.

The command to prevent pruning on a trunk port is:

     switchport trunk pruning vlan none

If you only have two switches in the set then it doesn't really matter.

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