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3850 switch not letting Cisco phones get Voice vlan IP

3850 switch not letting Cisco phones get Voice vlan IP, they just get an IP from the configured data vlan.

This is a stack of 2-3850's.  

We have other 3850's that are working fine with no problem.

I am going to try reloading the switches after hours.

The switches are running 3.03.05SE.

Same OS as the other working switch.

Any ideas?

Below is how the interface is configured.

interface GigabitEthernet1/0/34
switchport access vlan 68
switchport voice vlan 38
trust device cisco-phone
auto qos voip cisco-phone
spanning-tree portfast
service-policy input AutoQos-4.0-CiscoPhone-Input-Policy
service-policy output AutoQos-4.0-Output-Policy

itx-fl4-idf7-3850-s2#sh vlan

VLAN Name Status Ports
---- -------------------------------- --------- -------------------------------
1 default active Gi1/1/2, Te1/1/4, Gi2/1/1, Gi2/1/2, Te2/1/4
4 Server active Gi1/0/1
8 IT active Gi1/0/3, Gi1/0/4, Gi1/0/5, Gi1/0/6, Gi1/0/7, Gi2/0/23, Gi2/0/35, Gi2/0/44
12 WIRELESS active
16 Guest active
20 Operations active Gi1/0/11, Gi1/0/12, Gi1/0/29, Gi2/0/26
24 IS active Gi1/0/8, Gi1/0/9, Gi1/0/10, Gi1/0/14, Gi1/0/16, Gi2/0/10, Gi2/0/11, Gi2/0/12, Gi2/0/13, Gi2/0/14
Gi2/0/15, Gi2/0/16, Gi2/0/17, Gi2/0/18, Gi2/0/19, Gi2/0/21, Gi2/0/22, Gi2/0/24, Gi2/0/28, Gi2/0/30
Gi2/0/33, Gi2/0/34, Gi2/0/36, Gi2/0/37, Gi2/0/38, Gi2/0/41, Gi2/0/42, Gi2/0/43
28 Admin active Gi2/0/46
32 Voice active
36 Voice_Floor3 active
38 Voice_Floor4 active Gi1/0/1, Gi1/0/2, Gi1/0/3, Gi1/0/4, Gi1/0/5, Gi1/0/6, Gi1/0/7, Gi1/0/8, Gi1/0/9, Gi1/0/10, Gi1/0/11
Gi1/0/12, Gi1/0/13, Gi1/0/14, Gi1/0/15, Gi1/0/16, Gi1/0/17, Gi1/0/18, Gi1/0/19, Gi1/0/20, Gi1/0/21
Gi1/0/22, Gi1/0/23, Gi1/0/24, Gi1/0/25, Gi1/0/26, Gi1/0/27, Gi1/0/28, Gi1/0/29, Gi1/0/30, Gi1/0/31
Gi1/0/32, Gi1/0/33, Gi1/0/34, Gi1/0/35, Gi1/0/36, Gi1/0/37, Gi1/0/38, Gi1/0/39, Gi1/0/40, Gi1/0/41
Gi1/0/42, Gi1/0/43, Gi1/0/44, Gi1/0/45, Gi1/0/46, Gi2/0/1, Gi2/0/2, Gi2/0/3, Gi2/0/4, Gi2/0/5
Gi2/0/6, Gi2/0/7, Gi2/0/8, Gi2/0/9, Gi2/0/10, Gi2/0/11, Gi2/0/12, Gi2/0/13, Gi2/0/14, Gi2/0/15
Gi2/0/16, Gi2/0/17, Gi2/0/18, Gi2/0/19, Gi2/0/20, Gi2/0/21, Gi2/0/22, Gi2/0/23, Gi2/0/24, Gi2/0/25
Gi2/0/26, Gi2/0/27, Gi2/0/28, Gi2/0/29, Gi2/0/30, Gi2/0/31, Gi2/0/32, Gi2/0/33, Gi2/0/34, Gi2/0/35
Gi2/0/36, Gi2/0/37, Gi2/0/38, Gi2/0/39, Gi2/0/40, Gi2/0/41, Gi2/0/42, Gi2/0/43, Gi2/0/44, Gi2/0/45

itx-fl4-idf7-3850-s2#sh int trunk

Port Mode Encapsulation Status Native vlan
Po1 on 802.1q trunking 1
Po2 on 802.1q trunking 1

Port Vlans allowed on trunk
Po1 1-4094
Po2 1-4094

Port Vlans allowed and active in management domain
Po1 1,4,8,12,16,20,24,28,32,36,38,68,72,76,200,204-205,248,250,254,900,3000-3002,3333
Po2 1,4,8,12,16,20,24,28,32,36,38,68,72,76,200,204-205,248,250,254,900,3000-3002,3333

Port Vlans in spanning tree forwarding state and not pruned
Po1 1,4,8,12,16,20,24,28,32,36,38,68,72,76,200,204-205,248,250,254,900,3000-3002,3333
Po2 1,4,8,12,16,20,24,28,32,36,38,68,72,76,200,204-205,248,250,254,900,3000-3002,3333

itx-fl4-idf7-3850-s2#sh vtp status
VTP Version capable : 1 to 3
VTP version running : 1
VTP Domain Name : medsyn
VTP Pruning Mode : Disabled
VTP Traps Generation : Disabled
Device ID : 3462.88ae.4400
Configuration last modified by at 0-0-00 00:00:00

Feature VLAN:
VTP Operating Mode : Transparent
Maximum VLANs supported locally : 1005
Number of existing VLANs : 25
Configuration Revision : 0
MD5 digest : 0x41 0x57 0x3E 0x20 0x49 0x7A 0x1D 0x7F
0xC6 0x8E 0x02 0x5D 0x89 0xE6 0x63 0xE0

i reloaded the switch help!!

i guess i will open a case with TAC.

TAC case 638251409.

Cisco found in the configuration the below command:

no cdp advertise-v2

enabled it and it fixed the voice vlan problem...not getting IPs on the voice vlan.

Cisco Employee

Hi David,

Hi David,

I believe we are getting IP from DHCP server, right? Please share vlan 38 configuration.

Can we try to hard code vlan on IP Phone? Maybe DHCP is assigning IP in data vlan.

Run "debug ip packet" during non-business hours and shut/no shut the interface. (before this log this session)

Run Embedded captures on 3850 and perform shut/no shut.


Switch#monitor capture TEST interface gi1/0/34

 monitor capture TEST match ipv4  any any

 monitor capture TEST file location flash:mycap.pcap buffer-size 10

 monitor capture TEST limit packets 100

Once this is configured, you must start the capture. If a file already exists on the flash with this name, it prompts you if wish to overwrite this.

Switch#monitor capture TEST start

A file by the same capture file name already exists, overwrite?[confirm]

To check outputs

Switch#show monitor capture file flash:TEST.pcap

Switch#show monitor capture file flash:TEST.pcap detailed

You can also transfer file to your PC and run Wireshark to get detailed analysis. (Please share) Most probably packet is not being tagged properly.

In case if you have opened TAC case do share SR#


Vivek Sharma

Yes the IP is coming from the

Yes the IP is coming from the DHCP server  Yes the phones are getting IP address from DHCP server from Data VLAN.  Its the same DHCP server for voice and data.  My personal IP phone gets an address fine from the server  My phone is on a different switch stack, 3750.

Other 3850's are working fine with this type of configuration, same IDF.

I reloaded the switches.  No help!

I have not opened a case with TAC yet.  I might...maybe I can get the capture.  Good idea!




Older Cisco phones rely on CDP neighbour to obtain their voip vlan.

Can you check that the phones are CDP neighbors



Regards, Alex. Please rate useful posts.
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