Complete brain fade time - Vlan100 is up, line protocol is down

[sdawson35]

Im sitting here going quietly mad (actually I probably am already mad). We have lost management access to one of our switches (normal data and voice vlans are okay though).

When I look at the vlan I see

Vlan100 is up, line protocol is down
Hardware is EtherSVI, address is 0c11.6792.3041 (bia 0c11.6792.3041)
Description: *** Management ***
Internet address is 10.xx.xx.xx/24

sh interfaces trunk

Port Mode Encapsulation Status Native vlan
Po1 on 802.1q trunking 1

Port Vlans allowed on trunk
Po1 1-4094

Port Vlans allowed and active in management domain
Po1 1,45-48,57-58,100

Port Vlans in spanning tree forwarding state and not pruned
Po1 45-46

My config is 

interface Vlan100
description *** Management ***
ip address 10.xx.xx.xx 255.255.255.0
no ip route-cache

ip route 0.0.0.0 0.0.0.0 10.xx.xx.1

vlan 100
name VMB_Management

What am I missing ?

[Felipe A. Amaya]

Hi sdwason35,

You are allowing the VLAN across the port channel on your switch, can you check the other end to make sure that you are also allowing the VLAN 100.  

Hope this helps

[Moaz.Elzhrawey]

Hi,

I see for the show output that vlan 100 is not forwarding on spanning tree.

####   Port Vlans in spanning tree forwarding state and not pruned Po1 45-46 ####

So, could you please share the output of the following commands:
Show spanning-tree vlan 100

Show interface trunk

Show interface status.

My doubts here are:

1- You might not having spanning tree instance for vlan 100, if so, do this : SW(config)# spanning-tree vlan 100

2- Go to under vlan 100, and make no shutdown.

3- Make sure you have 1x access port in vlan 100 and the test again.

4- Is this switch part of VSS or VPC, or just standalone switch?

## Anyway, the show commands I requested will help to identify the problem.##

[Georg Pauwen]

Hello,

is this a layer 3 switch ? If not, you need to use the command:

ip default-gateway 10.xx.xx.1

[Richard Burts]

The essential piece of information might be this

Vlan100 is up, line protocol is down

There are two things that will bring a vlan interface to the up/up state

1) having at least one physical port active in the vlan

2) having the vlan active on a trunk

Since this is a management interface it is likely that there would not be physical ports assigned to the vlan. So the issue is why is vlan 100 not active on the trunk. I wonder if the issue might be on the neighbor switch. What we see so far on this switch looks appropriate, so it would be appropriate to look on the neighbor switch.

HTH

Rick

[Leo Laohoo]

Is there an active access port that is assigned to VLAN 100?

[sdawson35]

Sorted !

Sh interface trunk was showing the correct vlan was assigned to the physical interfaces, so I removed it and re added it and it started working , this has happened twice for me and once for my colleague, same switch type and same operating system version - time for an upgrade methinks. 

[Mark Malone]

Hi
you may have caused an STP recalculation by doing that which put the vlan 100 into FWD state allowing it to become up/up it may not be a software issues , what code are you running ?