On Mar 6, 23:27, Brad Salai wrote:
> Subject: Re: IT WORKS!!!

> > > one thing I noticed in a little preliminary testing is that arp -a
returns
> > > 192.168.42.1 incomplete  (I may have the ip address wrong, but the
incomplete
> >
> > Hmmm...  That's a bit odd, but probably nothing to be too worried about
> > unless it persists across a reboot with /netbsd and sync'd netbsd and
> > arp binaries.
> >
> I just tried it again, I haven't for a while since it has been working, and I
get:
> law:~>arp -a
> ? (192.168.42.1) at 2:60:8c:8:fd:8f permanent
> ? (192.168.42.255) at (incomplete)
>
> I don't know what the second line means, but there it is. The network seems
to work fine, I have httpd working as a proxy server. Things are -good-

arp - address resolution protocol, the system by which network protocol
addresses are mapped into hardware addresses.

The implementation of arp that we are using caches all of its requests (like
any good arp should), and the most recent response, to reduce network traffic.
Note that the requests are put in the cache as they are made, and then the
details are filled in later, thus preventing multiple arp requests for the same
data. You may also sometimes see messages from the kernel, complaining that the
hardware address for a certain network address has been changed. This happens
here sometimes when our backbone network fails, and we switch to the backup
routers - they have different ethernet addresses but use the same IP address.

The second line in the example given above can be broken down as follows:
 ? (192.168.42.255) at (incomplete)
 ^  ^^^^^^^^^^^^^^      ^^^^^^^^^^
 |        |              We don't have a hardware address for this address,
 |        |              although we have attempted to resolve it. i.e. it's
 |        |              an incomplete entry in the arp cache
 |        |
 |    The network address of this entry in the arp cache.
 |
The host name that this aaddress reverses to using the resolver. ? means that
the name couldn't be found.

So, the incomplete is nothing to worry about, your machine attempted to send an
IP packet to this address, but the arp entry is as yet incomplete, because the
host (or something else as its proxy) hasn't responded yet. The host might be
down, or slow, or the network may be congested etc. The entry will either be
completed or it should eventually expire from the cache.

Bernard.