we have a few cp 7971g-ge ip phones and are implementing NAC. when we plug a PC into the back of this phone, after 10minutes, the PC loses connectivity to the HSRP address and can no longer find its MAC address. we can ping the actual router address and devices on the local subnet. this does not happen behind 7960 phones. the thing is, none of the ports are being managed by NAC when this happens. and as soon as we shutdown the untrusted link, the PC regains connectivity to the default-gateway (HSRP address). any ideas?
I have this problem too.