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. 

To begin with, the interface on the NetBSD machine is configured via
/etc/netstart with ifconfig ed2 204.29.161.40 netmask 255.255.255.240.
The HP router at 204.29.161.41 is now reachable and it creates a proper
arp table entry.

When I then add the alias with 'ifconfig ed2 alias 10.0.0.33'
and 'route add 10.0.0.33 localhost', the HP router starts complaining
with the above error msg and after the original arp table entry 
expires, it refuses to talk.

Deleting the alias with 'ifconfig ed2 10.0.0.33 delete' does not 
correct the problem, only rebooting the NetBSD machine.

BTW, checking the arp table on a Telebit NetBlazer LS on the same network
shows that it created two entries for the NetBSD machines ethernet card, 
one with 10.0.0.33 and the other with 204.29.161.40.  Other machines, 
including 2 more NetBSD boxes show only an entry for 204.29.161.40 in
their arp tables.


-- 
Andreas Wrede                  Planix, Inc.
andreas@planix.com             Networking, System Administration, Consulting
http://www.planix.com          Toronto, Ontario, Canada