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Community Member

Discover inactive VLANs


I was wondering how you could discover inactive VLANs in a network (CatOS core)... 'sh cam dynamic' is what I could think of...

Thanks for your help



Re: Discover inactive VLANs

Hi Mark,

By inactive what exactly you mean? What I understand is if you have created any VLAN but no ports are assigned physically to that VLAN or there is no trunk carrying that vlan it will go into inactive state.

If that is what you are looking for you can run the command "sh vlan" and the output will be something like this

Console> show vlan

VLAN Name Status IfIndex Mod/Ports, Vlans

---- -------------------------------- --------- ------- ------------------------

1 default active 5 2/1-2


10 VLAN0010 active 18 6/1,6/3

11 VLAN0011 active 19 6/2

20 VLAN0020 inactive 20

Now if you check VLAN 20 is inactive in vlan databse because there is no ports physically assigned to vlan 20 not there is any trunk configured on this swsitch on which vlan 2o is allowed so this vlan will be in inactive state.

HTH, if yes please rate the post.


Community Member

Re: Discover inactive VLANs

OK, maybe I was not giving enough info. Say you arrive at a new client where they ask you to install a new 650x core. You can

1) copy all existing VLANs

2) check whether they still need all those VLANs

One thing would be to check if they exist on the L3 module, and than sh arp to check if there's anything active. (snapshotting; take several sh arp's) So all my VLANs are active because they are all on the trunk (old setup ;)

Re: Discover inactive VLANs

Hi Mark,

I am still not very sure of your point out here but any vlan created on switch need not necessarily exist on layer 3. One may create vlan at layer 2 but may not configure logical interface for that vlan on l3 module.



Community Member

Re: Discover inactive VLANs

Ankur, that's true. I was just thinking of ways to discover how to see whether a vlan is used or not.

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