I've had this problem on my NetBSD/Sparc for a while now but until recently 
I ignored it, It is now driving me insane!:

/home/neil:neil@doublesix>arp -a
doublesix.domino.org (194.70.52.66) at 8:0:20:d:38:23 permanent
router.domino.org (194.70.52.67) at 8:0:3:22:17:6a
genesis.domino.org (194.70.52.69) at 8:0:20:a:c3:15
? (194.70.52.255) at (incomplete)

/usr/home/neil:neil@doublesix>ifconfig -a
le0: flags=8863<UP,BROADCAST,NOTRAILERS,RUNNING,SIMPLEX,MULTICAST>
        inet 194.70.52.66 netmask 0xffffff00 broadcast 194.70.52.255
lo0: flags=8008<LOOPBACK,MULTICAST>
        inet 127.0.0.1 netmask 0xff000000 

/home/neil:neil@doublesix>netstat -rn 
Routing tables

Internet:
Destination      Gateway            Flags     Refs     Use  Interface
default          194.70.52.67       UGS         4     2519  le0
194.70.52        link#1             UC          0        0  le0
194.70.52.66     8:0:20:d:38:23     UHL         1      285  lo0
194.70.52.67     8:0:3:22:17:6a     UHL         1        0  le0
194.70.52.69     8:0:20:a:c3:15     UHL         0       75  le0
194.70.52.255    link#1             UHL         1       20  le0

Now if I attempt to ifconfig lo0 it does it fine:

lo0: flags=8009<UP,LOOPBACK,MULTICAST>
        inet 127.0.0.1 netmask 0xff000000 

also:

127.0.0.1        127.0.0.1          UH          0        0  lo0

is added to the routeing table.

Now as in /etc/netstart if I do:

route add $hostname localhost

(hostname being doublesix.domino.org)

/usr/home/neil:neil@doublesix>route add doublesix.domino.org localhost
writing to routing socket: File exists
add host doublesix.domino.org: gateway localhost: No such file or directory

/home/neil:neil@doublesix>route -v add doublesix.domino.org localhost
u: inet 194.70.52.66; u: inet 127.0.0.1; RTM_ADD: Add Route: len 108, pid: 0, 
seq 1, errno 0, flags:<UP,GATEWAY,HOST,STATIC>
locks:  inits: 
sockaddrs: <DST,GATEWAY>
 doublesix localhost
writing to routing socket: File exists
add host doublesix.domino.org: gateway localhost: No such file or directory


Why do I get this, the only possible reason I can think of is:

194.70.52.66     8:0:20:d:38:88     UHL         1      321  lo0


anyone got an idea why this is happening? by rights I should be able to add 
that route.

NetBSD doublesix.domino.org 1.0A NetBSD 1.0A (DOUBLESIX) #0: Thu May 25 23:31:16 BST 1995     neil@doublesix.domino.org:/usr/home/neil/NetBSD-current/src/sys/arch/sparc/compile/DOUBLESIX sparc

Regards,
Neil.

-- 
Neil J. McRae                                  Domino: In the glow of the night
neil@domino.org, neil@demon.net,  neil@domino.demon.co.uk, neilm@wonderland.org
 neil@gbnet.net, neilm@dismayl.org,  neilm@ibmpcug.co.uk, neil@tardis.ed.ac.uk