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New Member

Vlan on Router Question

Question SVI on a Router

I have the same situation going on, but my SVI interface is up down status

I have an HSRP environment and the primary router is providing the connectivity
when I look at the vlan database on the primary router the SVI interface is UP UP

The deference is that the vlan database contain the vlan in the vlan database.

Question

the secondary router SVI interface show UP DOWN is that because it does not have
the vlan interface in the vlan database. If so, once I add the vlan to the database; will the

SVI state chance to up up or is there any additional steps required to bring the interface

To an status of  UP UP

Thanks

Everyone's tags (2)
2 ACCEPTED SOLUTIONS

Accepted Solutions
Cisco Employee

Vlan on Router Question

Hi Ernest,

Yes, without creating the VLAN in the database, the SVI will remain UP/DOWN. The reason for this is that the VLAN database creates the actual Layer 2 VLAN whereas the SVI is a logical interface used to provide a logical Layer 3 interface for that VLAN. Without the actual Layer 2 VLAN the SVI cannot move to UP/UP because there are is no instance of the actual VLAN on the device. Once you create the VLAN in the database the interface should come UP/UP.

HTH

Anthony

Hall of Fame Super Silver

Vlan on Router Question

Hello Ernest,

until you don't add the Vlan in the Vlan database the L3 SVI is not operational.

The L2 VLAN has to be created in the database and a switchport either in access mode or in trunk mode has to be member of the L2 Vlan and up/up in order for the SVI to become up/up.

You need also to provide a L2 communication path between the two routers as they have to exchange HSRP messages on the common IP subnet,

Hope to help

Giuseppe

4 REPLIES
Cisco Employee

Vlan on Router Question

Hi Ernest,

Yes, without creating the VLAN in the database, the SVI will remain UP/DOWN. The reason for this is that the VLAN database creates the actual Layer 2 VLAN whereas the SVI is a logical interface used to provide a logical Layer 3 interface for that VLAN. Without the actual Layer 2 VLAN the SVI cannot move to UP/UP because there are is no instance of the actual VLAN on the device. Once you create the VLAN in the database the interface should come UP/UP.

HTH

Anthony

New Member

Re: Vlan on Router Question

Thanks Anthony

That is what I though; I will add it to the database tomorrow night. It has always been up down. From what I can tell for a long time years, just adding the vlan to the database will bring it up?

I just don’t understand why it did not add the vlan to the database when they add the switch port access vlan to the router sub interface. Any ideals or does it works different on a router?

Hall of Fame Super Silver

Vlan on Router Question

Hello Ernest,

until you don't add the Vlan in the Vlan database the L3 SVI is not operational.

The L2 VLAN has to be created in the database and a switchport either in access mode or in trunk mode has to be member of the L2 Vlan and up/up in order for the SVI to become up/up.

You need also to provide a L2 communication path between the two routers as they have to exchange HSRP messages on the common IP subnet,

Hope to help

Giuseppe

New Member

Re: Vlan on Router Question

Thanks Giuseppe

         I just never saw the router subinterface have the switchport access vlan on it before i amd us to seeing the
          enc dot1  vlan. I will let you know how it work out

          Thanks much

          blessing to you

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