Decimal nota8on by conven8on each byte in a 32 bit

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Unformatted text preview: 1.6 maps to mul2ple IP addresses for example: Mul2ple domain names mapped to the same IP address: Mul2ple domain names mapped to mul2ple IP addresses: Some valid domain names don't map to any IP address: Carnegie Mellon A Program That Queries DNS int main(int argc, char **argv) { /* argv[1] is a domain name */ char **pp; /* or dotted decimal IP addr */ struct in_addr addr; struct hostent *hostp; if (inet_aton(argv[1], &addr) != 0) hostp = Gethostbyaddr((const char *)&addr, sizeof(addr), AF_INET); else hostp = Gethostbyname(argv[1]); printf("official hostname: %s\n", hostp->h_name); for (pp = hostp->h_aliases; *pp != NULL; pp++) printf("alias: %s\n", *pp); for (pp = hostp->h_addr_list; *pp != NULL; pp++) { addr.s_addr = ((struct in_addr *)*pp)->s_addr; printf("address: %s\n", inet_ntoa(addr)); } } Carnegie Mellon Using DNS Program linux> ./dns official hostname: address linux> ./dns 128.2...
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