I've got a customer who recently upgraded their network gear. All their phones (Toshiba IP-5000 series and Polycom 7000s) are having a difficult time with DCHP (they work fine if set for static IPs btw).

What's happening is the phone sends a IP discover, the DHCP server sends the dhcp offer, the phone sends dhcp request but then the process repeats over and over until the phones exhaust all IP's in the DHCP scope or the until the IP lease time expires.

Phones are on a VLAN, their network switch ports are set for tagged and no VLAN number is configured in the phones.

I'm not the network engineer but apparently I have to figure this out as all he wants to do is blame the phones...