The talk consists of two parts. In the first part, we consider the Relativistic Vlasov-Maxwell System on a general axisymmetric spatial domain with perfect conducting boundary which reflects particles specularly, and look at a certain class of equilibria, assuming axisymmetry in the problem. We prove a sharp criterion of spectral stability under these settings and then provide several explicit families of stable/unstable equilibria. In the second part, we verify, for the 1.5D relativistic Vlasov-Maxwell system on an interval 0, 1), that for a plasma in a spatial domain with a boundary, the specular reflection effect of the boundary can be approximated by a large magnetic confinement field in the near-boundary region.