IP_MULTICAST_TTL(2const) — Linux manual page

IP_MULTICAST_TTL(2const)                         IP_MULTICAST_TTL(2const)

NAME         top

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

LIBRARY         top

       Standard C library (libc, -lc)

SYNOPSIS         top

       #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         top

       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         top

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

HISTORY         top

       Linux 1.2.

CAVEATS         top

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

SEE ALSO         top

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

COLOPHON         top

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Linux man-pages 6.18            2025-11-25       IP_MULTICAST_TTL(2const)

Pages that refer to this page: IPPROTO_IP(2const)

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