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Community Member

phone is not getting ip from Voice vlan + 3750 switch

Hi All ,


auto QoS is enabled on cisco 3750 switch and below is fast ethernet config on which polycom IP 6000 phone is connected..Till yesterday it was working fine means it got ip address from Voice subnet from remote DHCP server.

Today we noticed that it was trying to get an ip address from data subnet as well as voice subnet but after few minutes mac address is not showing on fast ethernet 1/0/34.


Note : we have checked with dhcp team about the scope defined on the "Remote " dhcp server which is fine.

interface FastEthernet1/0/34
 switchport access vlan 100
 switchport voice vlan 300
 service-policy input AutoQoS-Police-CiscoPhone
 srr-queue bandwidth share 10 10 60 20
 srr-queue bandwidth shape  10  0  0  0
 queue-set 2
 priority-queue out
 auto qos voip trust
 spanning-tree portfast

what could be the reason for not getting voice ip on the phone ? what else can be checked from switch end ..any idea would be appreciated.


Wuth Rgds,





Thanks , M S K
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Can you post the output to

Can you post the output to the command "sh power inline" and "sh cdp n <INTERFACE>"?

Community Member

The interface configuration

The interface configuration looks fine.


I suspect the DHCP scope is either exhausted, or something has changed at the server end.

1. Make sure addresses are available in the scope

2. Make sure ip helper addresses are enabled on any routers, layer 3 switch interfaces between the phone and DHCP server


Is the phone a SIP phone?

Can you check the display on the phone to verify that it is catching the voice vlan?

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