what does the "?" means - When I issue "arp -a " , I can see as followings.

Hi,

When I issue "arp -a " , I can see as followings.

? (192.168.3.222) at 00:01:02:8D:93:80 [ether] on eth0
? (222.112.196.68) at 000:B7:B6:C0:31 [ether] on eth1
? (222.112.196.69) at 00:02:55:AA:95:5E [ether] on eth1

I'd like to know what does the "?" means at first column?

Have a day.





somez72

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somez72 wrote:
> Hi,
>
> When I issue "arp -a " , I can see as followings.
>
> ? (192.168.3.222) at 00:01:02:8D:93:80 [ether] on eth0
> ? (222.112.196.68) at 000:B7:B6:C0:31 [ether] on eth1
> ? (222.112.196.69) at 00:02:55:AA:95:5E [ether] on eth1
>
> I'd like to know what does the "?" means at first column?

The first column is the hostname. If you specified the -n option to arp, or
the hostname can't be resolved, you get a questionmark in that column.


- --
Lew Pitcher

Master Codewright & JOAT-in-training | GPG public key available on request
Registered Linux User #112576 (http://counter.li.org/)
Slackware - Because I know what I'm doing.
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On Mon, 5 Dec 2005 09:41:00 +0900, somez72
<(E-Mail Removed)> wrote:
> Hi,
>
> When I issue "arp -a " , I can see as followings.
>
> ? (192.168.3.222) at 00:01:02:8D:93:80 [ether] on eth0
> ? (222.112.196.68) at 000:B7:B6:C0:31 [ether] on eth1
> ? (222.112.196.69) at 00:02:55:AA:95:5E [ether] on eth1
>
> I'd like to know what does the "?" means at first column?
>
It means the IP addresses have no known hostname, or arp uses the -n
option by default.

--
Fine's Corollary:
Functionality breeds Contempt.

then, How can we get hostname in first column?
I think, I nerver seen that host name in first colume?

Have a day.


> > Hi,
> >
> > When I issue "arp -a " , I can see as followings.
> >
> > ? (192.168.3.222) at 00:01:02:8D:93:80 [ether] on eth0
> > ? (222.112.196.68) at 000:B7:B6:C0:31 [ether] on eth1
> > ? (222.112.196.69) at 00:02:55:AA:95:5E [ether] on eth1
> >
> > I'd like to know what does the "?" means at first column?
> >
> It means the IP addresses have no known hostname, or arp uses the -n
> option by default.
>
> --
> Fine's Corollary:
> Functionality breeds Contempt.

On Tue, 6 Dec 2005 11:05:43 +0900, somez72 wrote:
> then, How can we get hostname in first column?
> I think, I nerver seen that host name in first colume?

$ arp -a
fw.home.invalid (192.168.2.1) at 00:A0:CC:26:06:34 [ether] on eth0

$ head /etc/hosts
127.0.0.1 localhost
192.168.2.1 fw.home.invalid fw
192.168.2.10 wb.home.invalid wb
192.168.2.12 wb1.home.invalid wb1

"somez72" <(E-Mail Removed)> writes:

> then, How can we get hostname in first column?
> I think, I nerver seen that host name in first colume?

Works for me...

snowball:548$ /usr/sbin/arp -a
elmyra.wb.comcast.net (192.168.0.15) at 00:60:97:C2:C2:95 [ether] on eth0
babs.wb.comcast.net (192.168.0.14) at 00:C0:F0:3E:49:F7 [ether] on eth0
zoya.wb.comcast.net (192.168.0.13) at 00:20:A6:57:75:84 [ether] on eth0
noodlenoggin.wb.comcast.net (192.168.0.11) at 00:50A:80:46:11 [ether] on eth0
pinky.wb.comcast.net (192.168.0.1) at 00:13:10:92:FE:52 [ether] on eth0
--
Joseph J. Pfeiffer, Jr., Ph.D. Phone -- (505) 646-1605
Department of Computer Science FAX -- (505) 646-1002
New Mexico State University http://www.cs.nmsu.edu/~pfeiffer
skype: jjpfeifferjr

On Mon, 05 Dec 2005 21:05:43 -0500, somez72 <(E-Mail Removed)> wrote:


>> > Hi,
>> >
>> > When I issue "arp -a " , I can see as followings.
>> >
>> > ? (192.168.3.222) at 00:01:02:8D:93:80 [ether] on eth0
>> > ? (222.112.196.68) at 000:B7:B6:C0:31 [ether] on eth1
>> > ? (222.112.196.69) at 00:02:55:AA:95:5E [ether] on eth1
>> >
>> > I'd like to know what does the "?" means at first column?
>> >
>> It means the IP addresses have no known hostname, or arp uses the -n
>> option by default.
>then, How can we get hostname in first column?
> I think, I nerver seen that host name in first colume?

There's no hostname to get. It tries to find one in DNS. If that's
your network, configure your DNS server to provide a name.