.\" @(#)rdisc.8c 1.4 96/1/22 FreeBSD '\"macro stdmacro .\" .\" Rdisc (this program) was developed by Sun Microsystems, Inc. and is .\" provided for unrestricted use provided that this legend is included on .\" all tape media and as a part of the software program in whole or part. .\" Users may copy or modify Rdisc without charge, and they may freely .\" distribute it. .\" .\" RDISC IS PROVIDED AS IS WITH NO WARRANTIES OF ANY KIND INCLUDING THE .\" WARRANTIES OF DESIGN, MERCHANTIBILITY AND FITNESS FOR A PARTICULAR .\" PURPOSE, OR ARISING FROM A COURSE OF DEALING, USAGE OR TRADE PRACTICE. .\" .\" Rdisc is provided with no support and without any obligation on the .\" part of Sun Microsystems, Inc. to assist in its use, correction, .\" modification or enhancement. .\" .\" SUN MICROSYSTEMS, INC. SHALL HAVE NO LIABILITY WITH RESPECT TO THE .\" INFRINGEMENT OF COPYRIGHTS, TRADE SECRETS OR ANY PATENTS BY RDISC .\" OR ANY PART THEREOF. .\" .\" In no event will Sun Microsystems, Inc. be liable for any lost revenue .\" or profits or other special, indirect and consequential damages, even if .\" Sun has been advised of the possibility of such damages. .\" .\" Sun Microsystems, Inc. .\" 2550 Garcia Avenue .\" Mountain View, California 94043 .\" .nr X .TH rdisc 8C "22 Jan 1996" .SH NAME rdisc \- network router discovery daemon .SH SYNOPSIS .B rdisc [ .B \-sfa ] .LP .B rdisc .B \-r [ .BI \-p " preference" ] [ .BI \-T " interval" ] .SH DESCRIPTION .IX "rdisc" "" "\fLrdisc\fP \(em ICMP router discovery daemon" .IX "Internet" "ICMP router discovery daemon" "" "ICMP router discovery daemon \(em \fLrdisc\fP" .IX "Internet Control Message Protocol" "See ICMP" .IX "ICMP" "router discovery daemon" "" "router discovery daemon \(em \fLrdisc\fP" .LP \f4rdisc\f1 implements the .SM ICMP router discover protocol. The first form of the command is used on hosts and the second form is used on routers. On a host \f4rdisc\f1 is invoked at boot time to populate the network routing tables with default routes. On a router it is also invoked at boot time in order to start advertising the router to all the hosts. .SS "Host (First Form)" .PP On a host \f4rdisc\f1 listens on the \f4ALL_HOSTS\f1 (224.0.0.1) multicast address for \f4ROUTER_ADVERTISE\f1 messages from routers. The received messages are handled by first ignoring those listed router addresses with which the host does not share a network. Among the remaining addresses the ones with the highest preference are selected as default routers and a default route is entered in the kernel routing table for each one of them. .LP Optionally, \f4rdisc\f1 can avoid waiting for routers to announce themselves by sending out a few \f4ROUTER_SOLICITATION\f1 messages to the \f4ALL_ROUTERS\f1 (224.0.0.2) multicast address when it is started. .LP A timer is associated with each router address and the address will no longer be considered for inclusion in the the routing tables if the timer expires before a new .I advertise message is received from the router. The address will also be excluded from consideration if the host receives an .I advertise message with the preference being maximally negative. .SS "Router (Second Form)" .PP When \f4rdisc\f1 is started on a router, it uses the \f4SIOCGIFCONF\f1 .BR ioctl (2) to find the interfaces configured into the system and it starts listening on the \f4ALL_ROUTERS\f1 multicast address on all the interfaces that support multicast. It sends out .I advertise messages to the \f4ALL_HOSTS\f1 multicast address advertising all its .BM IP addresses. A few initial .I advertise messages are sent out during the first 30 seconds and after that it will transmit .I advertise messages approximately every 600 seconds. .LP When \f4rdisc\f1 receives a .I solicitation message it sends an .I advertise message to the host that sent the .I solicitation message. .LP When .B rdisc is terminated by a signal it sends out an .I advertise message with the preference being maximally negative. .br .ne 1i .SH OPTIONS .TP 15 .B \-a Accept all routers independently of the preference they have in their .I advertise messages. Normally .B rdisc only accepts (and enters in the kernel routing tables) the router or routers with the highest preference. .TP .B \-f Run .B rdisc forever even if no routers are found. Normally .B rdisc gives up if it has not received any .I advertise message after after soliciting three times, in which case it exits with a non-zero exit code. If .B \-f is not specified in the first form then .B \-s must be specified. .TP .BI \-p " preference" Set the preference transmitted in the .I solicitation messages. The default is zero. .TP .B \-r Act as a router as opposed to a host. .TP .B \-s Send three .I solicitation messages initially to quickly discover the routers when the system is booted. When .B \-s is specified .B rdisc exits with a non-zero exit code if it can not find any routers. This can be overridden with the .B \-f option. .TP .BI \-T " interval" Set the interval between transmitting the .I advertise messages. The default time is 600 seconds. .SH "SEE ALSO" .BR routed (8C) .BR icmp (7), .BR inet (7) .LP Deering, S.E.,ed .RI `` "ICMP Router Discovery Messages" ,'' .SM RFC 1256, Network Information Center, .SM SRI International, Menlo Park, Calif., September 1991.