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HP-UX 11i Version 3: February 2007

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rdpd — router discovery protocol daemon (OBSOLETE)


rdpd [-r | -t | -v]


rdpd, the router discover protocol daemon, implements the host portion of the router discovery protocol (see SEE ALSO). More specifically rdpd:

  • solicits router advertisements when it is first started so as to populate the kernel table as soon as possible.

  • listens on all ethernet interfaces (that are up) for ICMP router advertisement datagrams.

  • adds a default router to the kernel table based on whether the router is a neighbor and has the highest preference among all advertisements received.

  • ages the default router entry applied to the kernel table based on the lifetime value found in the advertisement message.

rdpd can be started during boot-time initialization. To do so, see /etc/rc.config.d/netconf. (But see WARNINGS below.)


rdpd supports the following options:


Display the version of rdpd.


Enable tracing of the following events:

  • setting of expiration timer for advertised entry.

  • expiration of a router advertisement entry (only the active entry has a timer running).

  • add/update of an advertised router to the kernel.

  • removal from kernel table of an advertised router.

  • reception of a router advertisement from the link.

  • transmission of a router solicitation message.

  • failure while attempting to transmit a solicitation.


Enable verbose tracing, which in addition to the above, traces:

  • contents of the router advertisement message received.

  • contents of rdpd internal statics which includes:


    total number of icmp messages received,


    total number advertisements received,


    total number of advertisements with invalid number of addresses field,


    total number of advertisements with invalid address size field,


    total number of advertisements with invalid message lengths,


    total number of advertisements with invalid lifetime fields,


    total number of icmp messages with number of bytes received <> header length field.



The maximum number of default routes retained is 10. Only one of which is applied to the kernel routing tables (the one with the highest preference). In the event that the advertised router with the highest preference expires the retained advertised router list will be searched for the highest preference, still current entry and that entry will be applied to the kernel table. This allows for quick recovery from aged advertisements.


rdpd only becomes aware of link state changes when either a new Router Advertisement message is received or a timer pops to age a currently active default router added by rdpd. This may cause a delay between an interface state change (e.g., ifconfig down) and any necessary change to the kernel routing table.


The "all hosts on subnet" broadcast address is used for sending solicitations instead of either the all-routers multicast or limited-broadcast IP addresses.


The limited-broadcast address for inbound Advertisements is assumed.


Default routers added via the route command can be altered due to Router Advertisements for the same router.


Adding default routes via the route command can cause unpredictable results and should be avoided.


The functionality of rdpd has been subsumed in gated. See the routerdiscovery statements described in gated.conf(4). rdpd has been obsoleted in HP-UX 11i Version 2.


rdpd should not be used if routerdiscovery client is enabled when running gated.


rdpd was developed by HP.


gated(1M), gated.conf(4). [1] Deering, S., "ICMP Router Discovery Messages", RFC 1256

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