Cisco - VLAN status is up Line Protocol down

[mediaos718]

I have a weird issue here: Cisco 3750 vlan status is UP line protocol is down.

- The SVI exists

- The VLAN is int the vlan database

- The vlan is on the trunk port

- The trunk port is up

- I issue shut/no shut

- If I were to put a live interface on the VLAN then it will show UP/UP

Yet, the VLAN line protocol is down although the VLAN is on the trunk port.

Can anyone help? See config:

Vlan100                10.6.254.2      YES NVRAM  up                  down

interface Vlan100

ip address 10.1.254.2 255.255.255.252

interface Port-channel100

switchport trunk allowed vlan 100

end

Port-channel100 is up, line protocol is up (connected)

100  PS_Setup                        active

Spanning tree instance(s) for vlan 100 does not exist.

Group  Port-channel  Protocol    Ports

------+-------------+-----------+-----------------------------------------------

100    Po100(SU)       LACP      Gi1/0/23(P)

[paul driver]

Hello Georg

" Allowing a VLAN on a trunk is not enough you need to assign the port to that VLAN"

This isnt true, The svi will become active (up/up) as long as the trunk is active, it has a layer L2 created and it being allowed on the trunk. you DONT need a access port assigned to it related L3 Vlan

So in this case, it seems like either the trunk isnt active or the L2 isnt created on either side of the trunk

res
Paul

[Georg Pauwen]

Paul,

you are right. What I should have said is: simply creating the SVI and allowing the VLAN on the trunk interface does not make the SVI active. The VLAN needs to exist in the database (which is what happens automatically when you assign a port to the VLAN)...

Reading through the original post again, OP mentioned that the VLAN was already in the database, so my post was pointless indeed...:(

[Niklas Sauer]

Based on the output of the show interfaces command, possible problems can be fixed as follows:

If the interface is up and the line protocol is down, a problem exists. There could be an encapsulation type mismatch, the interface on the other end could be error-disabled, or there could be a hardware problem.

If the line protocol and the interface are both down, a cable is not attached or some other interface problem exists. For example, in a back-to-back connection, the other end of the connection may be administratively down.

If the interface is administratively down, it has been manually disabled (the shutdown command has been issued) in the active configuration.

[mediaos718]

The following commands need to be there for the SVI to come up -  did not have them at first:

"switchport trunk encapsulation dot1q

switchport mode trunk"

[Moses Fernandes]

Hello,

Thanks for sharing the solution. We truly appreciate it.

I thought that command has something to do with the trunk (encapsulation) and not VLANS.

Anyways glad to know that "#switchport trunk encapsulation dot1q" helped to resolve this resolved.
Learnt something new today.

Regards,

Moses.

[Eahwar34]

Actually I had this problem, but then I realized Spanning tree configs between the access and core switch is mismatching and once correcting it , automatically the vlan protocol came up. So checking spanning tree configs is worth for fixing the issue.