Issue with Cisco ip phones plugged into 9200L

[carl_townshend]

Hi Guys

we have come across an issue with one of our new switches, a Cisco 9200L, we have tried the latest firmware, 17.3.4 as well as 17.3.1

basically what we are seeing is the phone is not picking up dhcp when plugged into this switch, we see the MAC address and the phone in dsp neighbours, the switch port is configured for voice vlan.

if we plug the same phone or another model phone into another switch next to it it works fine, the config is identical on both switches.

any ideas what this could be?

[balaji.bandi]

Are both the switches the same model and the same IOS XE ?

1. do you have uplink port config trunk same config?

2. can you post interface config to look.

[carl_townshend]

Hi

it’s basically the below

switchport access vlan 10

switchport mode access

switchport voice vlan 20

spanning-tree portfast 

Auto qos voip Cisco-phone

The other switch is a 2960x

[Georg Pauwen]

Hello,

does Vlan 20 exist on the switch, and is the SVI for that Vlan reachable from that switch ?

[carl_townshend]

hi, yes to both 

[Georg Pauwen]

Hello,

make sure CDP is enabled on the switch...

[balaji.bandi]

Like to see full configuration if possible,

Auto qos voip Cisco-phone  - did this created any Global config ?

[Leo Laohoo]

Does any of the switch members of the stack have any SFP/SFP+ inserted?

[carl.townshend]

Hi, no they dont, its a single switch uplinked via copper

[Leo Laohoo]

Does the phone work in the same switch but different ports?

[carl.townshend]

Hi Guys

An update on this, we have had to log it with TAC and we are waiting for a response.

Basically we have seen that when we enable auto qos voip cisco-phone it stops working, we have done a packet capture and can confirm that when this command is enabled the switch is not sending any cdp packets, so the phone will never know which voice vlan to tag the packets with, this explains it.

I can only think it may be a bad batch of hardware as our older 9200Ls have this command and its running fine, even with the same firmware.

[Leo Laohoo]

---

@carl.townshend wrote:

Basically we have seen that when we enable auto qos voip cisco-phone it stops working, we have done a packet capture and can confirm that when this command is enabled the switch is not sending any cdp packets

---

Thanks for the update, @carl.townshend.  Keep us posted for any developments.  

[carl.townshend]

Hi All

TAC have come back with a fix for this, a special release of software 17.3.4.b was released week just to fix this issue. It only applies to hardware versions v02 and v03, so I was right in my initial thinking of that it was a hardware issue and a bug fix has been put in place to resolve it. Basically when the QOS was enabled, it caused all traffic to drop in the output queue.

It is a shame as this has taken 2 days of 2 engineers time to get to the bottom of it.

cheers

[Leo Laohoo]

---

@carl.townshend wrote:

It is a shame as this has taken 2 days of 2 engineers time to get to the bottom of it.

---

Pray this bug (CSCvz76172) is really fixed in 17.3.4b.  

[Scott Plank]

Thanks for updating this thread with your resolution - helped me out today when I ran into this issue with three 9200L-24 switches that I went to install and couldn't figure out why phones weren't working, but PCs plugged directly into the ports were. Upgraded one of the switches to 17.3.4b and the phone on it is working now. I never would have thought CSCvz76172 was the issue, based solely on the description of the bug.