topic Re: 9800-40/80 17.15.4 drops all MDNS advertisements in Wireless

9800-40/80 17.15.4 drops all MDNS advertisements

jasonm002 — Fri, 29 Aug 2025 14:08:30 GMT

9800-40/80 17.15.4 running local MDNS gateway drops all MDNS advertisements, services are being learned and cached correctly from wired sources but advertisements are always being dropped before they go out to clients. Can observe this happening in mdns trace logs after setting mdns trace level to verbose for wncd of interest, looks like it's failing to inject the MDNS packet for delivery by the hardware -or- in some specific configurations it's thinking that it's receiving an AAA override for mdns profile which it is verifiably not.

I have a TAC case open, but anyone else experiencing this or able to verify? Worked in 17.12.4, broken in 17.15.4. There was a behavior change in release notes involving SVIs for mdns services learned from wired hosts but I tried removing the SVI -- no change.

Re: 9800-40/80 17.15.4 drops all MDNS advertisements

MHM Cisco World — Fri, 29 Aug 2025 14:11:08 GMT

mDNS what is relate to AAA?

mDNS server is connect to same vlan of wifi client?

MHM

Re: 9800-40/80 17.15.4 drops all MDNS advertisements

Mark Elsen — Fri, 29 Aug 2025 16:23:09 GMT

- @jasonm002 Possible cause : https://bst.cloudapps.cisco.com/bugsearch/bug/CSCwh37134

Re: 9800-40/80 17.15.4 drops all MDNS advertisements

trapasso — Sat, 30 Aug 2025 17:41:25 GMT

Hello,

I have the exact same thing happening. Thursday evening I upgrade from 17.12.5 to 17.15.4. Friday morning I received a complain for a lab which used mdns no working. Glad I too the chance to do general search on the internet on this problem.

The lab does not have any wired components. It is just an isolated SSID on a separate vlan running mdns, all devices are wireless. Thursday the lab was working fine, Friday the devices cannot discover the other devices advertisements.

I opened a TAC case late Friday but I will be escalating since this lab equipment is part of University program and the term is starting next week.

If you want to share your TAC case I will share mine and maybe we can get our Engineers to talk.

Re: 9800-40/80 17.15.4 drops all MDNS advertisements

MHM Cisco World — Sat, 30 Aug 2025 18:28:14 GMT

Show mdns-sd cache <<- I need to see output of this

MHM

Re: 9800-40/80 17.15.4 drops all MDNS advertisements

Rich R — Sun, 31 Aug 2025 11:08:10 GMT

Check https://community.cisco.com/t5/wireless/mdns-gateway-on-9800-40-with-ios-xe-17-9-5/m-p/5120931/highlight/true#M272162

Re: 9800-40/80 17.15.4 drops all MDNS advertisements

jasonm002 — Sun, 31 Aug 2025 11:39:13 GMT

Hey can you try adding an SVI for that SSID's VLAN? I'm seeing this in MDNS traces on the WNCDs, looks like there was a behavior change in 17.15 related to this, wondering if it solves the problem if you try (in order):

1) just configure an SVI at all for that SSID's VLAN and shut it down

2) configure a valid IPV4 address for that SSID's VLAN and unshut it

3) configure valid mdns-sd gateway service policy on that SSID's SVI

seen in traces if you set mdns tracing level to verbose and then do an RA trace with "internal" enabled for a client:

(verbose): fetching src vlan for pref vlan 670

(ERR): Invalid bidb handle for vlan: 670

(debug): SVI IPv4 address not present for vlan 670, falling to default src intf

(verbose): src vlan 600 of default src intf as no mdns src intf or SVI

(ERR): L2_INJECT: Could not find client role for client :f6a1.707e.4055 <-- seems to be not the reason for the failure in my testing

(ERR): False from ioctl : lfts

(ERR): Unable to inject mdns packet

Re: 9800-40/80 17.15.4 drops all MDNS advertisements

MHM Cisco World — Sun, 31 Aug 2025 11:45:33 GMT

Show vlan breif

If vlan 670 not seeing add it by below

vlan 670
name VLAN670

Re: 9800-40/80 17.15.4 drops all MDNS advertisements

trapasso — Sun, 31 Aug 2025 17:02:12 GMT

Thanks for your suggestion. In my case I already had the SVI configured for the vlan with mDNS.

Re: 9800-40/80 17.15.4 drops all MDNS advertisements

MHM Cisco World — Sun, 31 Aug 2025 17:15:04 GMT

The SVI can config but you need to make sure the vlan and SVI is UP

Remember you do reboot after upgrading so it can vlan db is remove

MHM

Re: 9800-40/80 17.15.4 drops all MDNS advertisements

jasonm002 — Sun, 31 Aug 2025 18:45:38 GMT

I tried on a PSK WLAN on my end and created the SVI for that VLAN (671), gave it an IP, made sure it was up, and I also tried configuring the source-interface for mdns-sd gateway as WMI (Vlan600) globally, in each case the mdns trace with verbose level shows:

2025/08/31 14:04:55.456538587 {wncd_x_R0-0}{2}: [mdns] [20948]: (verbose): src vlan id 600 of src intf configured
2025/08/31 14:04:55.456539254 {wncd_x_R0-0}{2}: [mdns] [20948]: (verbose): Source IP4=10.3.20.4
2025/08/31 14:04:55.456541028 {wncd_x_R0-0}{2}: [mdns] [20948]: (ERR): L2_INJECT: Could not find client role for client :<mac>
2025/08/31 14:04:55.456543170 {wncd_x_R0-0}{2}: [mdns] [20948]: (ERR): False from ioctl : lfts
2025/08/31 14:04:55.456543482 {wncd_x_R0-0}{2}: [mdns] [20948]: (ERR): Unable to inject mdns packet

and

8/31 13:46:53.752760085 {wncd_x_R0-0}{2}: [mdns] [20948]: (verbose): fetching src vlan for pref vlan 671
2025/08/31 13:46:53.752761283 {wncd_x_R0-0}{2}: [mdns] [20948]: (verbose): src vlan id 671 of SVI for IPv4
2025/08/31 13:46:53.752762002 {wncd_x_R0-0}{2}: [mdns] [20948]: (verbose): Source IP4=10.4.119.254
2025/08/31 13:46:53.752766097 {wncd_x_R0-0}{2}: [mdns] [20948]: (ERR): L2_INJECT: Could not find client role for client : <mac>
2025/08/31 13:46:53.752769970 {wncd_x_R0-0}{2}: [mdns] [20948]: (ERR): False from ioctl : lfts
2025/08/31 13:46:53.752770498 {wncd_x_R0-0}{2}: [mdns] [20948]: (ERR): Unable to inject mdns packet

so it is complaining about client role, maybe the issue is it's triggering a code path for AAA override for MDNS inappropriately. I tried having AAA server send cisco-av-pair=role=something and in that case it STILL fails, but in that case it thinks it should receive an AAA override for mdns-sd policy which it does not receive because I don't want to do mdns-sd policy from AAA server, so AAA server never sends it.

Re: 9800-40/80 17.15.4 drops all MDNS advertisements

MHM Cisco World — Sun, 31 Aug 2025 19:07:23 GMT

https://bst.cisco.com/quickview/bug/CSCwd59093

Check this bug

Use workaround of this bug

MHM

Re: 9800-40/80 17.15.4 drops all MDNS advertisements

Rich R — Sun, 31 Aug 2025 21:57:01 GMT

That's the same advice as in the link I provided @MHM Cisco World

Re: 9800-40/80 17.15.4 drops all MDNS advertisements

trapasso — Tue, 02 Sep 2025 21:24:22 GMT

So just an update.
I worked with Cisco TAC today and it looks like a bug may have been discovered.
So a change in behavior was documented in the release notes between 17.15.3 and 17.15.4. even going through all the troubleshooting was not able to resolve the issue.
Rolling back to 17.15.3 and hoping mdns behaves. If not tomorrow night 17.12.5.

Re: 9800-40/80 17.15.4 drops all MDNS advertisements

jasonm002 — Wed, 03 Sep 2025 01:06:48 GMT

Thanks. What bug did TAC think it was, or are they creating a new one?

To everyone else: I don't think it's CSCwd59093 because I already have multicast link-local disabled.

Re: 9800-40/80 17.15.4 drops all MDNS advertisements

trapasso — Wed, 03 Sep 2025 04:34:29 GMT

They should be creating a new bug and I will post when I get the bug #

Re: 9800-40/80 17.15.4 drops all MDNS advertisements

MHM Cisco World — Wed, 03 Sep 2025 07:28:51 GMT

What important now is there any workaround for this bug or we need downgrade to solve it?

MHM

Re: 9800-40/80 17.15.4 drops all MDNS advertisements

trapasso — Wed, 03 Sep 2025 07:42:16 GMT

At this moment there is no workaround.

In my last post I mentioned that I am rolling back to 17.15.3, which I am performing now. I am hoping this will resolve the issues with mdns. I then have to troubleshoot with the lab coordinator to see if the equipment is working. I was planning on posting an update after testing the lab equipment.

Re: 9800-40/80 17.15.4 drops all MDNS advertisements

trapasso — Wed, 03 Sep 2025 17:07:38 GMT

I am going to ask a quick side question, not related to the mdns issue but related to the 17.15.4 code. When installed did anyone else see issues with APs getting stuck in a WLC Join loop with syslog message similar to "status 'upgrade.sh: Script called with args:[CANCEL]'" and "AP image version 17.15.4.18 backup 17.12.5.202, Controller 17.15.4.18". In an hour these messages occurred 245 times and the AP would join and disjoin the same number of times.
Curious if this others are having the mdns and the APs issues with code or it is just me.

Re: 9800-40/80 17.15.4 drops all MDNS advertisements

jasonm002 — Wed, 03 Sep 2025 17:37:10 GMT

I'm seeing stuff like

ap-name upgrade: Script called with args:[CANCEL]
ap-name upgrade: Cleanup tmp files ...
ap-name upgrade: Script called with args:[NO_UPGRADE]

when the AP even just rejoins the controller, looks like it's just cosmetic for me. Apparently occurring in 17.12.4 also according to my syslog history here.