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telnet delay

Posted on 2001-06-08
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Last Modified: 2008-03-04
I've got a pretty strange problem.
Every time i try to telnet to my linux box it takes like 20-40 seconds for the login prompt to come up.
I've got 2 nics in the linux machine, one for the cable modem and one for the lan (i use the linux box as a gateway).

Any ideas?
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Question by:nikitin
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Author Comment

by:nikitin
ID: 6168253
i run samba too, i takes long time to connect to the linux box from my win98 box.
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BlackDiamond earned 100 total points
ID: 6168748
This is usually caused by a DNS reverse-lookup failing for the ip that you are telneting from.  Try adding the ip of the client to the /etc/hosts file on your telnet server machine and giving it a name.
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by:nikitin
ID: 6168831
editing the hosts file made samba and telnet work great, but it still takes forever for the ftp to connect..
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by:dkloes
ID: 6169804
I have noted this also and just thought it was normal for ftp on Linux.  Unlike the old days, the ftp daemon only fires up when there is a request for ftp services.  I thought this may have been the reason for the delay.  I will be interested to here other responses.
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by:jlevie
ID: 6172295
If telnet and samba are fixed by adding entries to the hosts file, ftpd should use that also. The delay might be an ident request. The best way to find out what is happening would be to run a "tcpdump -n" on the linux box when you try an ftp connection.

Startup of ftpd from inetd/xinetd is, obviously, going to be slower than when ftpd is run as a daemon, but we're talking about times on the order of tenths of seconds on most boxes. Long delays, on the order of ten's of seconds are almost always going to be related to some sort of network activity.
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by:sudarshan1975
ID: 6175796
i have the same problem that is when my client machines telnet to server it takes some time to connect, u have suggested to use the hosts file to put the client details . but the clients are getting dhcp address from my server. IN this situation what could be the best solution. ALso when my clients do send and receive also, the time taken for this function to happen lots of time could u please let me know the solution for this

Regards

Sudarshan
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by:BlackDiamond
ID: 6179750
Sudarshan,
If you are using DHCP for a small block of addresses, then I would simply define a name for each ip of your dhcp block in the hosts file.  If you have a large block of addresses, then it would be better to set up a dns server.  There are ways of automating the naming schemes in the DNS zone files to handle blocks of IP's (perfect for exactly this purpose).  If you decide to pursue that route, and need additional help, let me know.  We should probably pursue that in a different question.

nikitin,
Not quite sure on your ftp problem yet.  I will try to replicate it when I get a chance, but might take me a couple days (pretty busy right now).  If anyone else has any insight, please feel free to chime in :-> ...
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by:The--Captain
ID: 6181515
I seem to recall a similar problem posted here a while back - IIRC, FTPd doesn't like to use the /etc/hosts file, even if the problems are DNS related.  

The solutions I suggested (I think one of them may have been accepted as an answer) were to create a bogus in-addr.arpa zone (if you're using RFC1918 IPs and control your own local nameserver), or otherwise get your in-addr.arpa zone for the host from which you're trying to connect to either resolve correctly or fail quickly (generally accomplished by hassling your ISP)...

Hope that helps,
-Jon

 
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by:RobertJenkins
ID: 6182849
I believe there are several things that can cause this delay...  Reverse Lookup of IP to DNS name can be one of the causes, but another cause is IDENT...  Try to shutdown ident and see if that helps...

On RedHat try this...

/etc/rc.d/init.d/identd stop
Stopping identd:   OK  ]

Helped on my system!!

Robert
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Author Comment

by:nikitin
ID: 6183388
Sorry Robert, stopping ident didn't work :(
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by:sudarshan1975
ID: 6184516
from my client machines they are not able to go to some ftp sites, why is this. iam using samba on my linux redhat7.0 server.
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by:The--Captain
ID: 6189654
nikitin: believe me - FTP is completely stubborn about DNS - I'm resonably certain that adding entries to /etc/hosts will not fix the FTP delay problem.

If you want to send me the IP address of the client (the machine that is seeing the delays) via email to jon@unixgroup.com, I will set up an in-addr.arpa zone on my nameserver that resolves that IP (or fails quickly <chuckle>) so you can see if DNS is your problem...

If you decide to do that, please include a valid email address so I can send you the IP of the nameserver to use.

-Jon

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by:The--Captain
ID: 6268571
nikitin - and the final solution was...?

A comment or explanation would be greatly appreciated.

Thanks,
-Jon

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