I am currently in the process of configuring an SG500-28P Small Biz switch and am having difficulties obtaining a DHCP address for a Cisco ATA SPA 122 device that's plugged directly into the switch. The ATA uses CDP to communicate with the switch, and shows up in the CDP neighbor details section, but it never sends a DHCPDISCOVER to the router that is acting as the DHCP server. I have "debug ip dhcp server packet detail" running on the router and can see when requests are hitting it.
The SG300 uses the following VLANS: 1 for DATA and 2 for VOICE. The ports are set to "untagged" for VLAN 1 and "Tagged" for VLAN 2 (with the exception of the Uplink port which is set to access in the data VLAN only. I also have IP helper configured on VLAN 2 to forward requests to the DHCP server on the router. If I plug an AVAYA phone set into one of the ports, it works as expected, the ATA receives an IP in the voice VLAN. The ATA, however doesn't. I've tried with both LLDP and CDP (both of which the ATA supports) and the same behavior is experienced on both.
The "auto voice vlan" feature is also enabled, and I have tried disabling it without any success as well for troubleshooting. Any suggestions on why the ATA wouldn't be getting an IP, but the AVAYA sets would with the same port configuration?