I am using CER with IP subnets to discover phones because our switches infrastructure are not supported by CER. there is a large campus with multiple buildings and subnets. most of the users are using extension mobility in different building. the problem is, CER discovers phones only once a day, if someone from buildingA login to a phone in buildingB, and immediately calls 911, CER sends wrong ELIN to PSAP.
if there is any work around, I'll be very appreciated to share with me.