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Quick Mail Log Question
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| amerar@iwc.net 2005-09-06, 6:04 pm |
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Hi All,
I, like everyone else, is getting this error message:
Unable to get canonical name of client 192.168.1.100: Unknown host
Question is, I have no idea on how to fix it. Everyone says it has
something to do with DNS, or Reverse DNS. Is that something I fix on
my own server, or my ISP fixes on theirs?
If I am to fix it on my server, how do I do that? I have no clue. Any
help would be appreciated.......
Thanks a bunch.
Arthur
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| Lion-O 2005-09-06, 6:04 pm |
| > Unable to get canonical name of client 192.168.1.100: Unknown host
> Question is, I have no idea on how to fix it. Everyone says it has
> something to do with DNS, or Reverse DNS. Is that something I fix on
> my own server, or my ISP fixes on theirs?
Depends on how you wish to solve this, and a lot also depends on the MTA
you're using. But fist lets see what this error means:
A 'canonical name' is another description of the full name of the host.
A host is usually described by a hostname + domainname (for example;
mail.google.com where 'mail' is the hostname, etc.). Another way to
describe this is the FQDN (Fully Qualified Domain Name).
Normally you lookup the IP number which belongs to a hostname/FQDN. This
can be done in a number of ways... The easiest way is to add this the IP
and the name to /etc/hosts. Another option is to use or setup a DNS
server. So summing up: you're basicly "linking" a name with an IP
adress.
However, it is also possible to do this the other way around. In other
words; "link" an IP adress with a name. Whenever you lookup the IP
adress you'll get the associated name. As you already mentioned yourself
its also called a 'reverse lookup'. Its called that way because "normal"
('forward') lookups are done by checking up on a name.
Now how to get rid of the message.. Most MTA's will try to lookup the
name of a host, in many cases MTA's are setup to only accept mail from
hosts which have a reverse name attached to them. The easiest way for
you to get rid of this is by telling your MTA not to do reverse lookups.
Another, more difficult, option is to install your own DNS server and
tell it that you'd like to 'associate' 192.168.1.100 with a name...
The option to disable reverse lookups on your MTA should be documented.
If you're considering to setup your own DNS server I'd like to point you
to the DNS Howto (http://www.tldp.org/HOWTO/DNS-HOWTO.html) as well as
the Bind9 documentation (http://www.isc.org/sw/bind/).
--
Groetjes, Peter
..\\ PGP/GPG key: http://www.catslair.org/pubkey.asc
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| Bill Marcum 2005-09-06, 6:04 pm |
| On 6 Sep 2005 07:45:14 -0700, amerar@iwc.net
<amerar@iwc.net> wrote:
>
> Hi All,
>
> I, like everyone else, is getting this error message:
>
I haven't seen it. Who do you mean by "everyone else"?
> Unable to get canonical name of client 192.168.1.100: Unknown host
>
> Question is, I have no idea on how to fix it. Everyone says it has
> something to do with DNS, or Reverse DNS. Is that something I fix on
> my own server, or my ISP fixes on theirs?
>
> If I am to fix it on my server, how do I do that? I have no clue. Any
> help would be appreciated.......
>
Is the address 192.168.1.100 listed in /etc/hosts? Do you have a DNS
server on your LAN?
--
Atlanta makes it against the law to tie a giraffe to a telephone pole
or street lamp.
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| amerar@iwc.net 2005-09-06, 6:04 pm |
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Well, I run my own mailserver. That IP address, 192.168.1.100 is the
IP of one of my internal machines. So, I'm not sure how it should be
listed in /etc/hosts.
I mean, it has no DNS and I'm not running my own DNS. So, I'm not sure
how to solve this. Also, what does MTA stand for???
Thanks,
Arthur
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| Barry Margolin 2005-09-07, 2:49 am |
| In article <1126040726.531160.38440@g47g2000cwa.googlegroups.com>,
amerar@iwc.net wrote:
> Well, I run my own mailserver. That IP address, 192.168.1.100 is the
> IP of one of my internal machines. So, I'm not sure how it should be
> listed in /etc/hosts.
192.168.1.100 host100.yourdomain.com
> I mean, it has no DNS and I'm not running my own DNS. So, I'm not sure
> how to solve this. Also, what does MTA stand for???
192.168.x.x addresses are private addresses, and they don't have any
mapping in the public DNS. So you need to either run your own internal
DNS server with these reverse entries, or add them to your /etc/hosts
file as above.
MTA stands for Mail Transfer Agent, the technical term for a mail server.
--
Barry Margolin, barmar@alum.mit.edu
Arlington, MA
*** PLEASE post questions in newsgroups, not directly to me ***
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| amerar@iwc.net 2005-09-07, 5:55 pm |
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A typical /etc/hosts file looks like this:
127.0.0.1 localhost.localdomain localhost
192.168.1.160 some.domain.com some
192.168.1.110 some2.domain.com some2
But, 192.168.1.100 is a windows box, which has no domain name. So, how
would I list in this the /etc/hosts file?
Thanks,
Arthur
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| Doug Freyburger 2005-09-07, 5:55 pm |
| amerar@iwc.net wrote:
>
> A typical /etc/hosts file looks like this:
>
> 127.0.0.1 localhost.localdomain localhost
> 192.168.1.160 some.domain.com some
> 192.168.1.110 some2.domain.com some2
>
> But, 192.168.1.100 is a windows box, which has no domain name. So, how
> would I list in this the /etc/hosts file?
All hosts with an IP number have a domain name if there
is even one associated host that has a domain name.
Get the hostname of the Windows box. Right click on
My Computer, select Properties. The Computer Name
tab will give the short name. It will not have any
spaces because spaces are forbidden in hostnames,
so if it is incorrectly named repair that damage.
Then add the name of the domain and there you go.
Register it in AD, NIS and/or DNS if you have any
of those in addition to the hosts file.
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| amerar@iwc.net 2005-09-07, 5:55 pm |
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Thanks, I'll try making that entry and see what happens. So, the
domain name is basically just the name of the Windows box......let's
see what happens.
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| amerar@iwc.net 2005-09-07, 5:55 pm |
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Thanks, I'll try making that entry and see what happens. So, the
domain name is basically just the name of the Windows box......let's
see what happens.
So, the /etc/hosts now looks like this:
127.0.0.1 localhost.localdomain localhost
192.168.1.160 some.domain.com some
192.168.1.110 some2.domain.com some2
192.168.1.100 windowsbox windowsbox
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| Doug Freyburger 2005-09-07, 5:55 pm |
| amerar@iwc.net wrote:
>
> Thanks, I'll try making that entry and see what happens. So, the
> domain name is basically just the name of the Windows box......let's
> see what happens.
>
> So, the /etc/hosts now looks like this:
>
> 127.0.0.1 localhost.localdomain localhost
> 192.168.1.160 some.domain.com some
> 192.168.1.110 some2.domain.com some2
> 192.168.1.100 windowsbox windowsbox
You missed the pattern.
192.168.1.100 windowsbox.domain.com windowsbox
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| amerar@iwc.net 2005-09-07, 5:55 pm |
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So, even though the windows box does not truely have a domain name I
still need the line:windowsbox.domain.com?
Well, since I have no idea, I'll trust you and make the
change..........
Thanks,
Arthur
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