4402 WLC Trunk/STP Issue

[john.judge]

Hello,

We have a few WLC's on our Network. The last WLC we deployed is having issues with connectivity. Persistent PING tests are showing drops every 20 packets or so. We noticed that the Mgt VLAN is flapping in STP.

The WLC is connected to a 4506 Switch 10/100/1000 mode. Auto negotiation is on and the port on both sides is 1000/Full. Having no issues with the others controllers.

4506 port config:

interface GigabitEthernet3/42

description Trunk to nyc1-32-wlc-02

switchport trunk encapsulation dot1q

switchport trunk allowed vlan 1,50-52

switchport mode trunk

VLAN 52 is the Mgt VLAN associated with the WLC. Any help would be appreciated. Thank you.

John

[ethiel]

Do you have multiple links from the controller connected currently? If so, did you enable LAG on the controller? It does not look like this 4506 port is set as a port-channel, so that could possibly be the issue.

-Eric

Please remember to rate all helpful posts.

[john.judge]

Hello Eric,

We have multiple links, but they aren't connected. Currently, we're dealing with Port 1 on 4506-1. LAG is disabled.

On our other WLC's, we have LAG disabled, Mgt Int port 1 backing up to port 2 and an AP-Manager on each port. Port 1 connects to 4506-1, Port 2 connects to 4506-2. Do you think having only port 1 connected might be the problem?

Thanks for your help.

[john.judge]

I connected Port 2 to 4506-2 and we're still having the same issue. It appears that the Mgt VLAN is being dropped from Spanning Tree.

ICMP packets are OK:

nyc1-32-4506-1#sh spanning-tree int gi3/42

Vlan Role Sts Cost Prio.Nbr Type

---------------- ---- --- --------- -------- --------------------------------

VLAN0001 Desg FWD 4 128.170 Edge P2p

VLAN0050 Desg FWD 4 128.170 Edge P2p

VLAN0051 Desg FWD 4 128.170 Edge P2p

VLAN0052 Desg FWD 4 128.170 Edge P2p

ICMP Packets time out:

nyc1-32-4506-1#sh spanning-tree int gi3/42

no spanning tree info available for GigabitEthernet3/42

After 4 time outs, the SPT on the interface comes back up.

nyc1-32-4506-1#sh spanning-tree int gi3/42

Vlan Role Sts Cost Prio.Nbr Type

---------------- ---- --- --------- -------- --------------------------------

VLAN0001 Desg FWD 4 128.170 Edge P2p

VLAN0050 Desg FWD 4 128.170 Edge P2p

VLAN0051 Desg FWD 4 128.170 Edge P2p

VLAN0052 Desg FWD 4 128.170 Edge P2p

nyc1-32-4506-1#

Before we enabled spanning-tree trunk fast, we got several time-outs (7 - 9), now we only get 4 (with it enabled).

Any idea? Thank you.

[Dinko Mihelcic]

Did you try to make management interface's vlan untagged on wlc(vlan0)and add switchport trunk native vlan 52 from other side as it is recomended in documentation

[john.judge]

Hello,

No, but that is a good idea. Do you happen to know what .PDF and page that is from? We used the 3.x guide when we originally configured the port and was under the impression that your approach is only recommended when using LAG mode.

BTW, the problem went away after swapping the SFP GBIC modules. They are from Cisco and I'm not sure why the pair we purchased is causing the problem. Once we installed two GBICs from a working WLC, the problem went away. Same firmware, same config. Odd...

Rgds,

John