This read-only Counter32, in units of table entries per its source description, counts the number of times an entry would have been added to the ptopoConnTable (e.g., from information learned via a topology protocol) but wasn't, due to insufficient resources. Admins treat a nonzero and growing TabDrops count as a capacity warning, indicating the device's topology table is hitting a resource limit and is failing to record some discovered neighbor connections. For example, a switch in a very densely connected topology showing rising TabDrops would need either a firmware limit increase or a reduction in the number of tracked connections.