%SW_DAI-4-DHCP_SNOOPING_DENY. help please

[Marc_AMI1]

Hello,

Today I had to change a stack of  2x 3750 switches by a stack of 2x 3750X. then linked the whole phones as they were linked to the first stack.

I copied the exact same run configuration from the first stack and add it the new stack.

When the new stack came up, the cisco phones coudn't work. however the PCs behind the phones worked.

I saw a lot of loggs like that on every port : %SW_DAI-4-DHCP_SNOOPING_DENY: 1 Invalid ARPs (Res) on Fa0/17, vlan.....

Can any one help please??????

Again, the switches had the same run configuration,

[mfarrenkopf]

You've got dynamic ARP inspection turned on.  If you weren't using it before, it should be turned off now.  To turn it off, try "no ip arp inspection."

If you want to have it on, it sounds like the telephone didn't re-DHCP for its address -- it came back up and began using the same address as before.  Are your telephones using PoE from the switch or do they have separate power injectors?  They're going to have to renew their DHCP leases so the switch can snoop the DHCP reply and see what the ARP entry is supposed to look like.  I'm guessing the PCs re-DHCP'd after moving the connections.