Nexus-Vlan

[kishrijal1]

Hi,

I am wondering that when I delete vlan from particular interface on Nexus 5548( version 3.3) ,why it delete vlan fom global mode? any suggestion will be appreciated.

Regards

Kish

[Masoud Pourshabanian]

Hello,

I am not sure I understood your question correctly or not. Configuration of VLAN is almost the same in all the switches(except old IOS version)

In switches you have ability to create some VLANs. By doing so,you create several broadcast domains. It is like making several switches from one switch. When you create VLAN ID globally, switch processes the incoming frames with that VLAN ID. Otherwise, switch drops those frames.

When you create a VLAN, you need to assign one or some interface to that VLAN.

Suppose we create VLAN 10 and assign interface 0/1 ind interface 0/2 in that VLAN. When switch receives traffic from interface 0/1, it only sends it to interface 0/2 and also trunk interfaces. it does not add any VLAN tag when it sends it to interface 0/2, but it adds tag ID 10 when it sends it to trunk interfaces.

Now your questions.

You assign some interfaces to a specific VLAN to make a virtual LAN. The interfaces in that VLAN only can talk to each other and also trunk interfaces. You remove one interface from an specific VLAN, if you do not want that interface to be part of that VLAN. Just remember if you remove an interface from a VLAN, that interface will be assigned to VLAN 1.

Why we delete a VLAN Globally.

If you have created a VLAN and does not have any interface assigned to that VLAN, switch still processes the incoming frames coming from trunk interfaces and sends them to other trunk interfaces. If you want your switch to drop those fromes, you need to delete that VLAN from global configuration.

Let me know if did not understand your quesion correctly.

Masoud

[kishrijal1]

Hello Masoud,

I really appreciated for yours quick reponse. I had issues on my office network last week which was solved now. The isuue was that I was planing to access vlan on some port in fex(2k nexus). I saw that the given port was accociate with differ vlan. In order to do that i went respective port interface and delete vlan from their but i lost vlan from all. ffor example,

interface eth101/1/2  already associate with vlan 20 but i need vlan 5 their.so,

interface eth101/1/2

no vlan 20 

switchport access vlan 5

switchport host

I lost vlan 20 from all connected device like (sap/c7000/mail server/sql server). I thought no vlan 20 is like no switchport access vlan 20. My senior enginner told me that nexus platform is differ than ios platform. so, even if you do no swichport.. you will lost all vlan.

[Masoud Pourshabanian]

Can you explain more.

Where you set no vlan 20. I think you set it in global mode instead of under interface. Is that right?

You mean if you set no switchport access vlan 20, you  will lose all VLAN 20?

Masoud

[InayathUlla Sharieff]

no vlan 20  >> these means you are deleted vlan from database.(Irrespective or location you are running this command it will remove from database. This is not the right command which you need to use whne you want to remove the vlan from the interface.

Please use " no switchport access vlan20 from interface to remove it).

HTH

Regards

Inayath

[paul driver · Accepted solution]

hello

The command no Vlan xx as stated by Will remove the vlan from the vtp database

You may have applied this command from at a interface level but this will still remove it.from the vtp database.

As again previously stated, To remove an interface from a specific vlan the command would need to be no switchport access vlan xx

Your post does highlight that your nexus 5548 is acting at a vtp server and because of this all other devices in this vtp domain received the latest summary advertisement from the server and updated their vtp database accordingly.

The only ways to negate this is either set all switches in vtp transparent mode ( which means manually administration of each switch vtp database)

or

Apply vtpv3 which will stop such changes you mentioned either from other vtp servers in the same domain because ONLY a vtp PRIMARY server can make changes to the vtp D/B

res
Paul