TCP question.

Eric Norum eric.norum at
Mon Apr 9 16:51:07 UTC 2001

Sergei Organov wrote:
> Using latest RTEMS snapshot I've noticed that when my board running RTEMS
> boots, it sends arp request of the form ('tcpdump' output, 'rcv' is board
> name):
> 20:03:42.041796 8:f3:3e:c2:7e:38 Broadcast arp 60: arp who-has rcv tell rcv
> As far as I understand, it asks outside world for its own Ethernet address
> (and probably is waiting for reply then?). This seems strange as Ethernet
> address is specified in the rtems_bsdnet_ifconfig structure. Is it a bug or
> feature?


If your RTEMS machine has changed its Ethernet or Internet address the
initial broadcast lets all other hosts on the segment flush any old,
incorrect, information from their ARP tables.  This is mentioned in an
RFC somewhere, but I don't have the exact reference handy.

Eric Norum                                 eric.norum at
Department of Electrical Engineering       Phone: (306) 966-5394
University of Saskatchewan                 FAX:   (306) 966-5407
Saskatoon, Canada.

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