IP_MULTICAST_TTL(2const)                              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.

SEE ALSO
       IPPROTO_IP(2const), setsockopt(2), ip(7)

Linux man-pages 6.17              2025-11-25          IP_MULTICAST_TTL(2const)