-#if vax || pdp11
-#define IN_CLASSA 0x00000080
-#define IN_CLASSA_NET 0x000000ff /* 8 bits of net # */
-#define IN_CLASSA_LNA 0xffffff00
-#define IN_CLASSB 0x00000040
-#define IN_CLASSB_NET 0x0000ffff /* 16 bits of net # */
-#define IN_CLASSB_LNA 0xffff0000
-#define IN_CLASSC_NET 0x00ffffff /* 24 bits of net # */
-#define IN_CLASSC_LNA 0xff000000
-#endif
+#define IN_CLASSA(i) (((long)(i) & 0x80000000) == 0)
+#define IN_CLASSA_NET 0xff000000
+#define IN_CLASSA_NSHIFT 24
+#define IN_CLASSA_HOST 0x00ffffff
+#define IN_CLASSA_MAX 128
+
+#define IN_CLASSB(i) (((long)(i) & 0xc0000000) == 0x80000000)
+#define IN_CLASSB_NET 0xffff0000
+#define IN_CLASSB_NSHIFT 16
+#define IN_CLASSB_HOST 0x0000ffff
+#define IN_CLASSB_MAX 65536
+
+#define IN_CLASSC(i) (((long)(i) & 0xe0000000) == 0xc0000000)
+#define IN_CLASSC_NET 0xffffff00
+#define IN_CLASSC_NSHIFT 8
+#define IN_CLASSC_HOST 0x000000ff
+
+#define IN_CLASSD(i) (((long)(i) & 0xf0000000) == 0xe0000000)
+#define IN_MULTICAST(i) IN_CLASSD(i)
+
+#define IN_EXPERIMENTAL(i) (((long)(i) & 0xe0000000) == 0xe0000000)
+#define IN_BADCLASS(i) (((long)(i) & 0xf0000000) == 0xf0000000)