topic Re: C9800 Mac Adress Conflict with WlClient in Wireless

C9800 Mac Adress Conflict with WlClient

florian.hanig1 — Wed, 20 Oct 2021 22:30:57 GMT

Hello,

I've a new installed C9800 Wifi Controller

GigabitEthernet1 is for Management and configured:

interface GigabitEthernet1
 no switchport
 ip address 10.2.99.250 255.255.255.0
 negotiation auto
 no mop enabled
 no mop sysid

Gigabit Ethernet2 ist the Trunk with SVI's...

interface GigabitEthernet2
 switchport trunk native vlan 1
 switchport trunk allowed vlan 30,90
 switchport mode trunk
 negotiation auto
 no mop enabled
 no mop sysid

And here are the SVI's:

interface Vlan30
 description "multimedia"
 ip address 10.2.30.250 255.255.255.0
 no mop enabled
 no mop sysid

interface Vlan90
 description data
 ip address 10.2.9.250 255.255.255.0
 no mop enabled
 no mop sysid

VLAN 30 + VLAN 90 are deployed via Flexconnect Local Switching in 2 seperate SSID's...

As long as the interface "GigabitEthernet2" is switched on, there are some failures in the Log:

%IOSXE-4-PLATFORM: Chassis 1 R0/0: cpp_cp: QFP:0.0 Thread:001 TS:000000006xxxxxxxxxxxxxxx %SWPORT-4-MAC_CONFLICT: Dynamic mac 001E.xxxx.xxxx from GigabitEthernet2 conflict with SVI, please check the network topology and make sure there is no loop.

The mac-adresses, they conflict are mac-adresses from some wifi Clients in VLAN 30 and 90...

How to do this configuration ?

I need the SVI for MDNS Gateway on the C9800 Controller...

Re: C9800 Mac Adress Conflict with WlClient

Mark Elsen — Thu, 21 Oct 2021 06:45:38 GMT

- FYI : https://bst.cloudapps.cisco.com/bugsearch/bug/CSCvt96686

Re: C9800 Mac Adress Conflict with WlClient

florian.hanig1 — Thu, 21 Oct 2021 07:03:54 GMT

I've already seen this bug...

But I have only one Wifi Controller in my Network... !?

And I'm on sw release 17.3.3.

On BST 17.3.3 is a fixed release for this bug..

Re: C9800 Mac Adress Conflict with WlClient

Mark Elsen — Thu, 21 Oct 2021 07:28:56 GMT

- Usually means that fragments of this bug are still applicable and or have not been completely resolved for your current wireless environment and or controller software version.

Re: C9800 Mac Adress Conflict with WlClient

florian.hanig1 — Thu, 21 Oct 2021 07:50:21 GMT

I can not imagine this...

So my version is the suggested version and my deployment is not a special deployment... ?!

Re: C9800 Mac Adress Conflict with WlClient

Arshad Safrulla — Thu, 21 Oct 2021 13:48:29 GMT

Can you remove the Native VLAN command under the physical interface and try?

Also I assume you are using a 9800-CL considering the port numbers in the logs shared, I recommend that you match the below in the port group config

Re: C9800 Mac Adress Conflict with WlClient

florian.hanig1 — Fri, 22 Oct 2021 07:49:12 GMT

I can later try to remove the native vlan in the inferface, but I think that's not the solution.

If i shut down GigabitEthernet1 and only GigabitEthernet2 is up, the mac address conflict message doesn't go away...

Settings in VMWARE are exactly what you posted in Screenshot...

Re: C9800 Mac Adress Conflict with WlClient

Arshad Safrulla — Fri, 22 Oct 2021 08:10:54 GMT

Best practices guide explicitly states that no native VLAN.

https://www.cisco.com/c/en/us/products/collateral/wireless/catalyst-9800-series-wireless-controllers/guide-c07-743627.html#:~:text=Wireless%20management%20interface%20VLAN%20tag

Also you must not mix Layer 3 ports and Layer 2 ports in the WLC, it is not designed to work like a router even though it is running similar code to a router. My recommendations are as below

1. Remove interface IP from Gig1 and configure it as a trunk

2. Assign the gig1 IP range to to VLAN1 and allow only vlan 1 in the trunk port connecting to gig1.

2. Remove native VLAN

Re: C9800 Mac Adress Conflict with WlClient

Rich R — Fri, 22 Oct 2021 10:25:25 GMT

"VLAN 30 + VLAN 90 are deployed via Flexconnect Local Switching in 2 seperate SSID's..."

So they should NOT be configured at all on the WLC!

You simply enter the VLAN number instead of an interface name in the "VLAN/VLAN Group" field of the Wireless Policy Profile.

On CLI:

wireless profile policy <POLICYNAME>

...

vlan XXX

...

This is documented at: https://www.cisco.com/c/en/us/support/docs/wireless/catalyst-9800-series-wireless-controllers/213945-understand-flexconnect-on-9800-wireless.html

"Step 2. Go to the Access Policies tab and type the VLAN (You do not see it in the dropdown list because this VLAN does not exists on the 9800 WLC)."

but it's really not made clear in the main configuration guide unfortunately.

If you want to use SVIs on the WLC then that is central switching not local switching.

Re: C9800 Mac Adress Conflict with WlClient

florian.hanig1 — Fri, 22 Oct 2021 10:53:49 GMT

Okay I understand.

But then it's not possible to use MDNS Gateway, right ?

With Flexconnect Local Switching the only option is MDNS Bridging ?

Because MDNS Gateway need's the local SVI's... !?

Re: C9800 Mac Adress Conflict with WlClient

Arshad Safrulla — Fri, 22 Oct 2021 12:26:19 GMT

As @Rich R highlighted you don't need SVI's in WLC for Flexconnect VLANs. What you are referring is valid only for Local mode AP's or Flex central switching.

In your case mdns gateway will be the L3 interface for that particular vlan (could be your core switch, firewall or router)

Re: C9800 Mac Adress Conflict with WlClient

Scott Fella — Fri, 22 Oct 2021 14:28:54 GMT

Take a look at the guide for mDNS for FlexConnect on the 9800

Cisco mDNS Technical Guide for Cisco Catalyst 9800 Series Wireless Controllers

Once you figure that piece out, then you need to review what the others have mentioned and figure out how you will design your network. Seems like you might not understand how FlexConnect is used on the 9800's. Just try to understand the basics then assess what you have to change to get clients authenticated to the correct vlan and also mDNS working as expected.

Re: C9800 Mac Adress Conflict with WlClient

m.yildiz — Wed, 24 Nov 2021 23:50:00 GMT

Hi,

did you resolve the issue?

i have the same issue.

Gruss

Re: C9800 Mac Adress Conflict with WlClient

Alex Pfeil — Mon, 21 Feb 2022 15:36:35 GMT

I shutdown VLAN 1 with similar configuration and I have not logged the issue since. I was not sure if that would be a solution. I will monitor it for the rest of the day and see.