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Interface VLAN down

I add VLAN and interface vlan with no shutdown command on MSFC but when i put show ip interface brief comand I have down and down. What cause this problem ??


Re: Interface VLAN down

The vlan is not in the vlan database

You can either manually add it to the vlan database or it will add a entry when you assign a port to that vlan. If the switch is in vtp mode of client you will have to create it manually on a server switch

Re: Interface VLAN down

Hi Friend,

As updated by tdrais you have to create vlan first at layer 2 level which you can do going to vlan database mode or on vlan config mode.

Now once vlan is created then you have to make sure that there is atleast one port assigned to that vlan or you have atleast one trunk configured allowing that vlan and then only the layer 3 interface for that vlan will come up.

HTH, if yes please rate the post.



Re: Interface VLAN down

Another thing to look at is the internal trunk between your MSFC and your switch. Do a show trunk and you will see a trunk for 15 and or 16. On that trunk you should be allowing the vlan you are referring to. If not then it will show up as down.down on your msfc. If this is the case then you need to allow that vlan on the trunk.....Good Luck...


Re: Interface VLAN down

It will also show down/down if you have no active ports in that vlan .


Re: Interface VLAN down

I guess I should have been more clear in my answer but didn't want to cause confusion.

Now I have not tried this lately on a catos box so it may be different

If a port is down/down it means there is no entry in the vlan database for it. It normally also means that there is no port assigned to that vlan also but you can accomplish this by assigning a port and then deleteing the vlan database. Either way you will get a down/down condition.

Once you add the vlan to the database the interface will go UP/DOWN. This means there is no active access port on the switch and the vlan is not allowed on any trunks that may be up.

Once a vlan becomes active either on a trunk or access port it goes to up/up

Part of the confusion with this is that cisco adds entries to the vlan database automatially when you add access ports to a unkown vlan.

The problems come when someone sees this down/down condition on a switch and checks that they allow all vlans on a active trunk port and it still doesn't work. In this case all you do is add the vlan database entry and it will come up.