Strange issues with 7841 Cisco phones

[amrutwell]

Recently we switched from Cisco 7940 phones to 7841. We're also using Catalyst 3850 switches, 4 PoE and 2 non on version 16.09.06/ However, the 7841 phones just stay stuck at "Verifying connection" when they're mounted to the wall and plugged into a wall port. I've checked the config of the port and all looks good there and if I plug a laptop into the same port it draws an IP address and works fine. I would think something to do with DHCP or something up with the VLAN but if I plug the phone directly into the switch into the same port that its respective wall port is patched from it comes up fine. Not really sure where to go next.

[balaji.bandi]

how is your config on the  interface where the phone connected. do the CDP enable in the switch ?

post below information ;

show run interface gi x/x

show run | in cdp

show run interface vlan X (voice vlan)

show run interface vlan Y (Data VLAN)

[M02@rt37]

Hello @amrutwell,

Call manager Express ou CUCM as call center ?

Do you re create the config files since MAC addresses has changed ? You need to regenerate XML files.

When a phone is plugged on the wall, how is the port on the Switch? 

Please double check the config port on the Switch (access vlan / voice vlan).

[Jonathan Schulenberg]

If the IP Phone works correctly when directly connected to the same switch port that the wall jack is normally cross-connected to it’s a cabling issue. A notable difference between the 7940 and 7841 is that the latter supports 1Gbps Ethernet - which uses all four pairs for data. You may want to try hard coding the phone and switch port to 100Mbps full duplex to see if that works around the faulty cabling.