This read-write integer, ranging 15 to 600 seconds, sets the maximum time before an entry in the ctCDPNeighborTable is aged out if no refresh is received, and the agent may adjust its own hold time based on values received from neighbors to keep the table stable relative to their transmit frequency. An administrator tunes this to control how quickly stale neighbor entries are purged from the table after a neighbor stops advertising or goes offline. For example, if neighbor entries linger too long after a device is physically disconnected, the admin lowers this hold time to age out stale entries more promptly.