ASSERT (FIB_NODE_INDEX_INVALID != fib_index);
vec_validate (ip4_main.fib_index_by_sw_if_index, sw_if_index);
ip4_main.fib_index_by_sw_if_index[sw_if_index] = fib_index;
ASSERT (FIB_NODE_INDEX_INVALID != fib_index);
vec_validate (ip4_main.fib_index_by_sw_if_index, sw_if_index);
ip4_main.fib_index_by_sw_if_index[sw_if_index] = fib_index;