IP_MULTICAST_TTL(2const)

NAME

IP_MULTICAST_TTL - time-to-live value of outgoing multicast packets

LIBRARY

Standard C library (libc, -lc)

SYNOPSIS

#include <netinet/in.h>  /* Definition of IP* constants */
#include <sys/socket.h>

int setsockopt(int sockfd, IPPROTO_IP, IP_MULTICAST_TTL,
               const int *ttl, sizeof(int));
int getsockopt(int sockfd, IPPROTO_IP, IP_MULTICAST_TTL,
               int *ttl, sizeof(int));

DESCRIPTION

Set or read the time-to-live value of outgoing multicast packets for this socket.

The default is 1 which means that multicast packets don't leave the local network unless the user program explicitly requests it.

ERRORS

See IPPROTO_IP(2const). See setsockopt(2). See ip(7).

HISTORY

Linux 1.2.

CAVEATS

It is very important for multicast packets to set the smallest TTL possible.