+struct igrphdr {
+ uint8_t ig_vop; /* protocol version number / opcode */
+#define IGRP_V(x) (((x) & 0xf0) >> 4)
+#define IGRP_OP(x) ((x) & 0x0f)
+ uint8_t ig_ed; /* edition number */
+ uint16_t ig_as; /* autonomous system number */
+ uint16_t ig_ni; /* number of subnet in local net */
+ uint16_t ig_ns; /* number of networks in AS */
+ uint16_t ig_nx; /* number of networks ouside AS */
+ uint16_t ig_sum; /* checksum of IGRP header & data */
+};
+
+#define IGRP_UPDATE 1
+#define IGRP_REQUEST 2