VLANs not deleted?

[Noora]

I'm working on removing some VLANs from our core switch. I removed a few last IMW, and today I did a <show interfaces vlan 200> and the vlan, that I thought I removed, is showing:
Vlan200 is up, line protocol is down , Autostate Enabled
Hardware is Ethernet SVI, address is (redacted)
Description: NAME
Internet address is (internal IP address)
MTU 1500 bytes, BW 1000000 Kbit/sec, DLY 10 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive not supported
ARP type: ARPA, ARP Timeout 04:00:00
Last input 12w3d, output 12w3d, output hang never
Last clearing of "show interface" counters never
Input queue: 0/375/0/0 (size/max/drops/flushes); Total output drops: 0
Queueing strategy: fifo
Output queue: 0/40 (size/max)
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
0 packets input, 0 bytes, 0 no buffer
Received 0 broadcasts (0 IP multicasts)
0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
1 packets output, 60 bytes, 0 underruns
Output 0 broadcasts (0 IP multicasts)
0 output errors, 1 interface resets
0 unknown protocol drops
0 output buffer failures, 0 output buffers swapped out

When I do <show vlan id 200> or <show vlan name NAME> I'm told it's not in the current VLAN database. I'm confused as to why it is showing up when I do <show interfaces vlan 200> but not <show vlan id> or <name>. I checked the vlan.dat file and it is not in there, so why is it still showing on the switch? Any thoughts greatly appreciated!

[balaji.bandi · Accepted solution]

not sure can you post  below output :

show vlan

show vtp status

After removed vlan as below :

no vlan 200

no interface vlan 200

have you write the config ?

[Jon Marshall · Accepted solution]

Two different things. 

Removing the vlan at L2 (no vlan <vlan ID>) will not remove the L3 interface for that vlan. 

You need to do "no int vlan 200".

Jon

[Noora]

Thank you Jon! That might have been where I went wrong.

[Richard Burts]

Jon is quite right to point out the difference between removing the layer 2 vlan (which you did) and removing the layer 3 vlan interface (which you need to do if not done yet). But that is probably not enough. I expect that if you perform commands like show ip interface brief that the vlan interface will still show up. It does not show up in the output of show run but does show up in the output of some show commands.

The explanation is that while we tend to think of running config as if it were a file with text in it, the running config is actually a dynamic data structure. When you configured the vlan interface it created an entry in the data structure. When you delete the vlan interface the entry is still in the data structure and it will remain until you reload. The reload creates a new data structure without that entry.

[Joseph W. Doherty]

As @Richard Burts notes, especially with VLANs, you often need to do a reload to get a clean slate.  BTW, there's are a couple of other instances, of configuration "things", where you need to reload to reset to a default/initial option for some feature.

Also BTW, in theory, if Cisco can add/support a feature dynamically (i.e. adding something like data structure, as Rick also notes), they should be able to remove it too.  However, my guess is, Cisco felt it wasn't worthwhile to totally clean up after activation/deactivation.  For example, with VLANs, it would be annoying to have to reload every time you add one or modify one, but when you delete them, other than a "ghost" of what was, what you're doing isn't impacted by Cisco not removing "whatever" was added to support it.  (Something similar, within many file or database structures, i.e. adding new data might require a whole bunch of processing.  A bunch of processing might also be needed for the converse, removal, but for removal, often "removed/deleted" data is just flagged as no longer in use.)

[Noora]

Thank you again everyone! I ran the commands the past maintenance window and the switch no longer have the vlans showing. A reboot of it will have to happen later.

[Richard Burts]

I am glad that you have done the commands and that the vlan interface is no longer in the running config. I am curious if you do show ip interface brief, is the interface gone or is it still in that output?

[Noora]

It's gone. And that's without a reboot. Thankfully.

[Richard Burts]

Thank you for confirming that the vlan interface does not show up on the output of show commands. I am pleasantly surprised that a reboot was not needed.