cmMACTTL is a read-only integer reporting how many minutes remain before a learned MAC entry ages out of the bridge table if no further traffic is seen from it. An administrator checks this to understand how current a given MAC-table entry is likely to remain, since a low value means that host will soon disappear from the table unless it sends more traffic. For example, if cmMACTTL for a device shows just 1 minute remaining, the operator knows that host has been quiet and will drop from the table shortly unless it resumes activity.