> After adding an IP alias, my  HP Router (27289A, 240/FR) rejects arp
> packets form the NetBSD machine with 'Invalid ARP Source: 10.0.0.33 on
> 204.29.161.41' and subsequently refuses to talk to it. 

Some "clever" boxes, like ciscos (alledgedly) and it seems your HP router
think they know what is best and tell you that the above is an error.

Hassle HP and ask them how to turn this "feature" off. Aliases do not
contradict any RFC I know of, so this router may not be "industry
standard".

Regards,
-- 
Peter Galbavy                                           peter@wonderland.org
@ Home                                                 phone://44/973/499465
in Wonderland                              http://www.wonderland.org/~peter/
                               snail://UK/NW1_6LE/London/21_Harewood_Avenue/