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Weird 7940 to 3560 problem

I dont know if it is switch or phone related. We have a few 7940 and 7960 phones at one location that will not get their vlan information from the switch. I have tried several things including turning the port into a trunk, and still the phone gets its IP information from the data vlan. Now here is the weird part, the arp table on the router will show that is has the IP address from the voice vlan, and the dhcp pool shows the bindings, yet CDP neighbor detail shows it has an IP from the data side.

Device ID: SIP0015634D2A9A

Entry address(es):

IP address:

Platform: Cisco IP Phone 7960, Capabilities: Host Phone

Interface: FastEthernet0/47, Port ID (outgoing port): Port 1

Holdtime : 177 sec

Version :


advertisement version: 2

Duplex: full

Power drawn: 6.300 Watts

Management address(es):

Internet 3 0015.634d.2a9a ARPA FastEthernet0/1.2

If I remove switchport access vlan 3 from the port, the phone gets the IP from the DHCP pool and registers, but I am unable to pull up the web interface of the phone. I can add switchport access vlan 2 back in, and if a PC is plugged in, it goes back to where it was before.

One other item, may or may not be related, I get constant trust resets from all the phones,

*Mar 1 20:03:30.687: %SWITCH_QOS_TB-5-TRUST_DEVICE_LOST: cisco-phone no longer detected on port Fa0/4, port set to untrusted.

*Mar 1 20:03:36.937: %SWITCH_QOS_TB-5-TRUST_DEVICE_DETECTED: cisco-phone detected on port Fa0/2, port trust enabled.

These are 7912 phones which are working properly.

Hall of Fame Super Gold

Re: Weird 7940 to 3560 problem

Hi, which IOS version on the switch? Can you upgrade to latest and try again ?

Community Member

Re: Weird 7940 to 3560 problem

I think c3560-ipbasek9-mz.122-25.SED1.bin is the latest, it was upgraded to see if it was IOS related, Maybe version related? it has IP base in it, but I found some of our others are advipservices. This is the first time we have encountered this on any 3560 switch.

Hall of Fame Super Gold

Re: Weird 7940 to 3560 problem

Hi, both switch and phone are at latest.

would suggest you to try a factory reset on the phone, but you are using SIP images of which I'm not sure how will request image files, that would be no issue if using SCCP.

Community Member

Re: Weird 7940 to 3560 problem

I believe they already did a factory reset, I will verify though.

Community Member

Re: Weird 7940 to 3560 problem

Can you send the full configuration for the switchport you have this phone plugged into?

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