Network mask - determine the portion of address which is the host and the network - ex) 1 : network, 0 : host - class A : 11111111.00000000.00000000.00000000 - class B : 11111111.11111111.00000000.00000000 - class C : 11111111.11111111.11111111.00000000 - Local or Remote ? 1) Local - Same network 2) Remote - Different network - cisco devices does not support discontiguous mask (only contiguous) ..