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nr(7)									 nr(7)

       nr - Redundant Array of Independent Network Adapters (NetRAIN)

       The  NetRAIN  virtual  interface	 configures multiple interfaces on the
       same LAN segment into a single interface.  One of the  real  interfaces
       is always active while the others remain idle.  If the active interface
       fails, an idle interface comes online.  The failover time is adjustable
       depending on your network configuration and operation.

       You  can	 configure  the NetRAIN interface with the ifconfig command or
       with the ioctl system call.  See ifconfig(8) for more information.  You
       can also adjust some NetRAIN default parameters with the sysconfig com‐
       mand.  The SIOCIFADD ioctl parameter creates the NetRAIN virtual inter‐
       face  and adds the real interfaces to this NetRAIN set.	After creating
       the NetRAIN virtual interface, one or more real interfaces are attached
       to  it.	NetRAIN uses the Network Interface Failure Finder (NIFF) traf‐
       fic monitoring facility to monitor the interfaces. See  nifftmt(7)  for
       more information.

       You  can add or remove individual interfaces from the set, or disassem‐
       ble the entire set by using the ifconfig command.

       The following list of ioctl parameters is  used	to  configure  the  nr
       interface:  Creates the NetRAIN virtual interface if it has not already
       been created.  This parameter requires an if_nrset  structure  for  the
       arg  parameter  (found in the <net/if.h> file).	The if_nrset structure
       contains the name of the nr interface (nr0, nr1, ...)  and  a  list  of
       interfaces to attach to the NetRAIN set.	 Upon successful completion of
       this command, the NetRAIN set is configured and the  monitoring	thread
       is  activated.  If  the	command	 fails, the name of the interface that
       could not be added is copied back into the user space buffer (for error
       message generation).

	      The  list	 of  NetRAIN interfaces is kept in a static table. The
	      default size is specified by the nr_maxdev kernel attribute. The
	      interfaces  themselves  are  numbered from 0 to nr_maxdev-1 (for
	      example, nr0, nr1, ...).	To change  the	size  of  this	table,
	      change  the nr_maxdev attribute for the netrain kernel subsystem
	      by using the sysconfig command.  You must reboot the system  for
	      the new value to take effect.  Removes one or all members of the
	      NetRAIN set.  This command requires an ifreq structure with  the
	      ifr_name	field  set to the NetRAIN interface name (nrx) and the
	      ifr_index field set to the interface index of the	 interface  to
	      be  removed  from	 the  set (the ifreq structure is found in the
	      <net/if.h> file).

	      You can find the interface index of an interface	by  using  the
	      SIOCGIFINDEX  ioctl.   If the specified interface is the current
	      active interface in the NetRAIN set,  the	 active	 interface  is
	      switched	to another NetRAIN set member.	If the NetRAIN set has
	      only one member, removal of this member is equivalent to	disas‐
	      sembling the NetRAIN set.

	      If the ifr_index field is set to 0, the NetRAIN set is disassem‐
	      bled, the UP flag	 is  cleared  on  all  members,	 the  hardware
	      address  is reset to the default value, and the hardware address
	      is cleared for the nr interface.	You can reuse the nr interface
	      in  a  future  SIOCIFADD	command.   Forces  a  manual switch to
	      another interface in the NetRAIN set. This command  requires  an
	      ifreq  structure	passed	in  the	 arg  field  (<net/if.h>). The
	      ifr_name field can be the nr interface name or the name  of  any
	      member in the set. If the name is the nr interface or the active
	      member, the next member in the set is  brought  online.  If  any
	      other  member is specified in the ifr_name field, that interface
	      is brought online.  Retrieves the members of a NetRAIN set. This
	      command  requires	 an if_nrset structure to be passed in the arg
	      field (<net/if.h>).  The nr_name field may be the	 nr  interface
	      name  or	the  name  of  any member of the set. Upon return, the
	      nr_name field contains the nr  interface	name  and  the	nr_buf
	      field  is	 a  list  of  member  names. This buffer must be large
	      enough to hold all the members or an ENOBUFS error is  returned.
	      Forces  the  active  interface  to  switch to the next available
	      interface at regular intervals.  It requires an ifreq  structure
	      in  the arg field. The ifr_name field must contain the nr inter‐
	      face name and the ifr_value field contains an integer number  of
	      seconds  between each switch operation. A value of zero disables
	      this feature.

       The following ioctl parameter is used to control the interface monitor‐
       ing  frequency.	 This  parameter requires an mif_t structure (found in
       the <net/if.h> file). The name field  contains  the  NetRAIN  interface
       name  and  the t1 and t2 fields contain timer values.  Sets two NetRAIN
       interface timing parameters in the mif_t structure.  The	 t1  parameter
       specifies  the time period, in seconds, that the traffic monitor thread
       delays between reads of the interface counters when the network is run‐
       ning normally.  If there is no change in the received byte count for t1
       seconds, the traffic monitor thread issues a yellow alert.  The	recom‐
       mended t1 value is 4.

	      The t2 parameter specifies the traffic-free time period, in sec‐
	      onds, that must pass before the traffic monitor thread  declares
	      the interface dead.  The recommended t2 value is 10 for Ethernet
	      interfaces and 16 for Asynchronous Transfer Mode (ATM) LAN  Emu‐
	      lation (LANE) interfaces.

       The  NetRAIN virtual interface supports all other ioctl parameters. The
       NetRAIN driver propagates these commands	 to  the  real	device	driver
       where  appropriate.  See	 the reference page for each individual driver
       for more details.

       NetRAIN has the following restrictions: You must	 construct  a  NetRAIN
       set  out	 of  interfaces that are currently idle. This means the inter‐
       faces cannot be marked as "up" in the Set up Network Interface  Card(s)
       dialog  box  of	the  SysMan  Menu  and	they  cannot have IP addresses
       assigned to them.  You must use two or more of the same type of network
       interface  (FDDI, ATM LAN Emulation, or Ethernet) dedicated to a single
       LAN segment.  If you use Ethernet adaptors, theymust all be of the same
       speed.  You cannot run LAT over a NetRAIN virtual interface (nr) or any
       of the interfaces that compose a NetRAIN set.  Run separate cables from
       each  network  interface to the appropriate hub or concentrator to pro‐
       vide physically redundant paths back to the network.  This reduces  the
       chance  of  network failure due to cables being accidentally unplugged.
       If necessary, you can adjust the timeout values to ensure that  NetRAIN
       will  successfully  detect and respond to network failure. You can tune
       these parameters with the sysconfig command, ifconfig command, and  the
       ioctl  system  call.   See  nr(7), ifconfig(8), sysconfig(8), dxkernel‐
       tuner(8), and sys_attrs_netrain(5) for more information.

	      By default, these parameters are tuned for operation over Ether‐
	      net,  but	 it is possible that the default values and other sug‐
	      gested timeout values will not work  in  your  environment.  For
	      example,	if  you	 are connected to a switch, failover time will
	      depend on the switch and its configuration.  You	must  use  UNI
	      Version  3.1 when running NetRAIN over LANE to obtain acceptable
	      failover times with some ATM switches, including the Gigaswitch.
	      If  you  use  UNI	 Version  3.0, the failover time might be long
	      because the T309 timer is set to 90 seconds by default  on  some
	      switches.	 If  the  T309 timer is adjustable on your switch, you
	      can set the T309 timer to 10 seconds as in UNI  Version  3.1  to
	      try to achieve acceptable failover times.

       A specified interface is already configured.  Possible reasons include:
       The interface list contained an invalid interface type.	All interfaces
       must  be	 either FDDI or Ethernet.  The interface list contained inter‐
       faces of different types.  Interfaces must be either all	 FDDI  or  all
       Ethernet.   NetRAIN  could  not allocate system memory for the request.
       Possible reasons include: The NetRAIN interface name was invalid or the
       unit number was out of range (0 to nr_maxdev-1).	 An interface that was
       previously specified already belongs to a NetRAIN set.

       The following example creates a NetRAIN set from the  specified	inter‐
       faces.	The first argument is the NetRAIN virtual interface name, nrx.
       The second argument is a comma-separated list of real  interfaces  that
       are added to the NetRAIN set.

       #include		  <stdio.h>    #include		  <errno.h>   #include
       <sys/socket.h> #include	      <sys/ioctl.h> #include	    <net/if.h>

       #define IFNAMSZ 16

       int main(int argc, char *argv[]) {
	   struct if_nrset ifnrset;
	   char *addr;
	   nrset_t *buf;
	   int sock,i;

	   if (argc <= 2) {
	       printf("Usage: add <nrdev> <dev1>[,dev2...]0);
	   /* Load the NetRAIN interface name */
	   if (--argc > 0) {
	   /* Count the members to be included in the NetRAIN set */
	   if (--argc > 0) {
	       addr = *argv;
	       ifnrset.nr_cnt = 1;
	       for (i = 0; addr[i] != ' '; i++) {
		   if (addr[i] == ',') {
		       addr[i] = ' ';
	       /* Allocate a buffer large enough to hold the  interface	 names
	      buf = (nrset_t *)malloc(ifnrset.nr_cnt * IFNAMSZ);
	       if (buf == NULL) {
		   perror("malloc: ");
	       /* Load the interface array */
	       for (i=0; i<ifnrset.nr_cnt; i++) {
		   addr += strlen(addr)+1;
	       ifnrset.nr_len = ifnrset.nr_cnt * IFNAMSIZ;
	       ifnrset.nr_buf = (nrset_t *)buf;

	       sock = socket(AF_INET, SOCK_DGRAM, 0);
	       if (sock < 0) {
		   perror("socket: ");
	       if (ioctl(sock, SIOCIFADD, (char *)&ifnrset) != 0) {
		   perror("SIOCIFADD: ");

	   return(0); }

       Functions: ioctl(2)

       Interfaces:  alt(7),  bcm(7),  ee(7),  faa(7),  fta(7),	fza(7), le(7),
       ln(7), tu(7)

       Commands: nifftmt(7), ifconfig(8), sysconfig(8)

       Tuning: sys_attrs_netrain(5)

       Network Administration: Connections

       System Configuration and Tuning


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