telnet

[roland brouwers]

>>Ted Potter wrote:
>>
>>
>>>On Tue, 2005-03-29 at 09:23, roland brouwers wrote:
>>
>>[snip]
>>
>>
>>>>Now, as to why ME behaves differently, I suspect it has to do with
> 
> the
> 
>>>>terminal emulation in its telnet protocol.  One of the last things a
>>>>login does is set the prompt string and many systems will "eat" the
>>>>first prompt, just due to the way they set up the connections.  I'll
>>
>>bet
>>
>>
>>>>that it's not necessary for a "CTRL-C", but a simple "ENTER" would
> 
> get
> 
>>>>you the prompt.
>>>>
>>>>Can you fix it?  Probably not.
>>
>>
>>>>As I told you before "ENTER" doesn't work and it is getting worse.
It
>>
>>is
>>
>>
>>>>like eating my network. More and more workstations, even XP are
>>
>>waiting
>>
>>
>>>>on telnet. If you wait long enough they continue. Some workstations
>>
>>that
>>
>>
>>>>hat this problem do not anymore. What is this, PACKMAN?
>>
>>
>>It's "PacMan" (no "k").  :-)
>>
>>First, let's do some preliminary stuff.  Get on the Linux machine and
> 
> do
> 
>>some network probing.  Start out with "netstat -an | grep :23" to see
>>how many current telnet sessions you have running.  By default, you're
>>limited to 60 concurrent connetions.
>>
>>Next, by default, the system will try to log the remote hostname.  If
>>your DNS isn't doing reverse lookups or you don't have the Windows
>>boxes' IP addresses and hostnames in the Linux server's /etc/hosts
> 
> file,
> 
>>the system will wait for DNS to time out before allowing the session
> 
> to
> 
>>continue.
>>
>>Ok, how to fix?  Well, if you have more than 60 concurrent sessions,
> 
> you
> 
>>have to ask yourself if that's a legitimate use (60 telnet sessions is
>>a LOT, but it depends on your usage).  If you need more, you need to
> 
> go
> 
>>into /etc/xinetd.d and edit the "telnet" file.  If you need, say, 100
>>concurrent telnet sessions, add in a line that reads:
>>
>>	instances             = 100
>>
>>If you are having DNS issues, you can disable DNS-related things by
>>changing the line:
>>
>>	log_on_failure        += USERID
>>
>>to:
>>
>>	log_on_failure        =
>>
>>Also, add a line:
>>
>>	log_on_success        -= HOST
>>
>>If you started with the original /etc/xinetd.d/telnet file, it should
>>look sort of like this after all the editing:
>>
>># default: on
>># description: The telnet server serves telnet sessions; it uses \
>>#       unencrypted username/password pairs for authentication.
>>service telnet
>>{
>>         disable = no
>>	instances       = 100
>>         flags           = REUSE
>>         socket_type     = stream
>>         wait            = no
>>         user            = root
>>         server          = /usr/sbin/in.telnetd
>>         log_on_failure  =
>>	log_on_success  -= HOST
>>}
>>
>>Once you're done with editing the file, save it and execute:
>>
>>	/etc/rc.d/init.d/xinetd restart
>>
>>to make xinetd use the new data.
>>------------------------------------------------>
>>I will continue tomorrow this installation and I have to solve it.
>>So I have some questions:
>>How can I know that the linuxserver is using DNS, can I trace it?
> 
> 
> DNS is always used if the hostname or IP address in question isn't in
> the /etc/hosts file.
> 
> 
>>The names of the workstations are not in /etc/hosts. I am using
> 
> K12ltsp
> 
>>which fills it up automatically with some names. Do I have to empty
> 
> it?
> 
> Uh, no.  /etc/hosts should contain the names and IP addresses of
> machines that aren't in the DNS system.
> 
> 
>>If one client is going somewhere on the internet to look for the
> 
> server
> 
>>and other clients don't, how can I trace this.
> 
> 
> I'm not sure what you mean by this.  When you try to hit a website or
> something on the internet, the first thing the machine does is check
its
> /etc/hosts file to see if it has the address.  If it doesn't, then the
> system queries the DNS system to get the address.
> 
> The only way to trace it is to do a tcpdump on the machine in
question:
> 
> 	tcpdump port 53
> 
> That will show any DNS queries or responses sent over the network.
> 
> 
>>The server has 2 network cards, one of them is not used at this
> 
> moment,
> 
>>could this be a problem?
> 
> 
> It rather depends on the routing and how you have things set up.  We'd
> need to see a network diagram to tell you what's going on.
> 
> 
>>I only in the testphase, so I am far away from 60 users, so this
>>couldn't be the problem.
>>
>>Thanks again for any help that will get this network into discipline.
> 
> ----------------------------------------------------------->
> On all workstations I always get immediately the login prompt, then I
> enter the userID and the password and then he waits. 
> How can DNS play his role on that moment? The server is found, so why
> isn't he happy and continuous instead of waiting? And why does he do
> this for only some guys or girls? ):-8
> 
> What does Linux do, after entering the UserId and password?

Again, unless you remove the HOST stuff from /etc/xinetd.d/telnet, once
you log in the system will try to reverse resolve the IP address that
the user came in on and match it to a host name.

If the IP address ISN'T in the /etc/hosts file, it queries the DNS
servers listed in /etc/resolv.conf for the information.  It will wait
for up to 1 minute for an answer.  If no answer comes, it tries the next
server in that list.  This continues until all of the servers have been
tried or the DNS system gives an answer.

> I hope when I wake up tomorrow, the sun will shine.

It should, unless we have a nuclear war or major volcanic event.
----------------------------------------------------------------------
Nothing of this all worked.
Apparently the problem lies somewhere els.
In this network there is a Mswindow 2003 Domain Server which is
configured as a wins server.
I disabled named on the LinuxServer and pointed named.conf to the
Mswindows server, which makes no sense because I disabled named service,
by service named stop.
How can both live together without disturbing one eachother.
Because I use samba and configured some printers as smb printers I need,
I suppose, the wins server.
What is the right way to make a symbiosis.

I am still praying.
---------------------------------------->>>>>>>>>>>>>>>
The problem is solved. My client uses a windows2003 as DNS server, which
only does forward lookups. When they replaced some pc's, apparently they
did give them another IP address, so the DNSserver had problems with
those, not on the first place because of telnet, but because K12ltsp
start a ltspinfo script when you do telnet. I did not find out why.

ANOTHER QUESTION??????????????????????

I tried to connect some ms-win-workstations on the network with:
Mount -t smbfs -ousername=xxxxx,password=yyyyyy //mypc/c /mnt and this
gives an error. All the workstations belong to a mswin domain. My
portable which is not part of the domain is connected,without any
problem.

Any ideas?????