The diatomic linear chain with nearest-neighbor spring constants C1 and C2 has topologically different bulk states for C1 ≷ C2. A finite chain of N unit cells and fixed ends (the first and last spring is C1) exhibits two topological end states within the gap for C1 > C2.We investigate the effect of an impedance mismatch by varying the first and last ‘boundary’ spring constant termed CF from its ideal value C1. CF = 0 represents an open end and does never lead to topological states. CF→∞means that also the next site to the boundary is fixed, leading to topological states only for C1 < C2 since now the first movable spring is C2. Within a range of CF around C1 topological end states are preserved for C1 > C2. For C2 > C1, topological end states occur when CF exceeds a certain value.