MAC Address on the wrong VLAN and switchport

[michael_kiiru]

Dears,

Why would a switch report the same mac address of a host (IP Phone) on two VLANs on the same switchport?

switch#sh mac address-table  inter Fa2/0/38
          Mac Address Table
-------------------------------------------
Vlan    Mac Address       Type        Ports
----    -----------       --------    -----
  51    0014.****.****    STATIC      Fa2/0/38
  51    0023.****.****    STATIC      Fa2/0/38
 151    0014.****.****    DYNAMIC     Fa2/0/38
Total Mac Addresses for this criterion: 3
switch#

vlan 51 is the data vlan and 151 is the voice vlan.

The port config is herebelow..

Current configuration : 138 bytes
!
interface FastEthernet2/0/38
 switchport access vlan 51
 switchport mode access
 switchport voice vlan 151
 spanning-tree portfast
end

Assistance appreciated.

Thanks.

[Ton V Engelen]

Hi

is it a Cisco phone? 

If so configure: 

interface FastEthernet2/0/38

cdp enable

[michael_kiiru]

Thanks John, Ton...

This is quite clear... done exactly as advised.. and it still doesn't seem to behave...

switch#sh mac address-table  inter Fa2/0/38
          Mac Address Table
-------------------------------------------

Vlan    Mac Address       Type        Ports
----    -----------       --------    -----
  51    0014.****.****    DYNAMIC     Fa2/0/38
  51    0023.****.****    DYNAMIC     Fa2/0/38
 151    0014.****.****    DYNAMIC     Fa2/0/38
Total Mac Addresses for this criterion: 3
switch#
switch#conf t                             
Enter configuration commands, one per line.  End with CNTL/Z.
switch(config)#interface FastEthernet2/0/38
switch(config-if)#cdp enable                 
switch(config-if)#end
switch#
switch#sh mac address-table  inter Fa2/0/38
          Mac Address Table
-------------------------------------------

Vlan    Mac Address       Type        Ports
----    -----------       --------    -----
  51    0014.****.****    DYNAMIC     Fa2/0/38
  51    0023.****.****    DYNAMIC     Fa2/0/38
 151    0014.****.****    DYNAMIC     Fa2/0/38
Total Mac Addresses for this criterion: 3
switch#
switch#conf t                             
Enter configuration commands, one per line.  End with CNTL/Z.
switch(config)#interface FastEthernet2/0/38
switch(config-if)#
switch(config-if)#shut
switch(config-if)#
switch(config-if)#no shut
switch(config-if)#
switch(config-if)#end
switch#
switch#
switch#sh mac address-table  inter Fa2/0/38
          Mac Address Table
-------------------------------------------

Vlan    Mac Address       Type        Ports
----    -----------       --------    -----
  51    0014.****.****    DYNAMIC     Fa2/0/38
  51    0023.****.****    DYNAMIC     Fa2/0/38
 151    0014.****.****    DYNAMIC     Fa2/0/38
Total Mac Addresses for this criterion: 3

[johnd2310]

Hi,

When the phone first connects to the switchport, it is not aware of the voice vlan and is placed in the data vlan. cdp/lldp then informs the phone of the voice vlan and the phone transitions to the voice vlan. For this reason, the mac address of the phone appears on the data vlan and the voice vlan.

Thanks

John

[corinthian]

FWIW, johnd2310, posted the correct answer.