This field holds the old IP address that identifies which chassis's circuits need to be re-pointed to a new IP, used as part of a two-step swap (paired with circuitNewIpAddrToSwap) when a chassis carrying multiple circuits is physically relocated and re-addressed. Because every circuit terminating on that chassis was provisioned referencing its old address, this object triggers the device to walk through and update all of them, and the description explicitly warns this causes temporary traffic loss as each circuit is brought down and back up. For example, an admin relocating a chassis from 10.1.1.5 to 10.2.1.5 would set this object to 10.1.1.5 and circuitNewIpAddrToSwap to 10.2.1.5, expecting a brief outage on every circuit that referenced the old address while they're each re-established.