ftp/telnet fails, then starts working again

[Sheri Gearhart]

Has anyone experienced the anomaly where ftp and telnet will stop working for a period of time then start working again?

There are no errors in the ftp servers logs, nor the ftp clients logs.

[Jordan Bean]

Please explain what you mean by "fail". Are connection attempts refused? Do they timeout? If connections are made, how far along the session do they typically go?

[Jordan Bean]

Also, are home directories accessed via NFS? Are you using DNS and/or NIS? If so, how well do these perform?

[Ray Brewer]

Are you attempting to ftp/telnet through a firewall? Also can you ping the affected server consistantly?

[Mihails Nikitins]

The answer is 'it depends'. FTP and Telnet are just high level network services, there may be 1000 reasons for problems. First, invsetigate if FTP and Telnet clients have instant connectivity to the server (ping may be a good test). Secondly, look at the server side (e.g. try 'telnet 127.0.0.1' on the server). From your post it is unclear what really fails. Do your sessions freeze or you just cannot establish new connections?

BR,
Mihails

[Sheri Gearhart]

When attempting to ftp to the client, there is no connection made. The ftp server states "trying".

The ftp client can be pinged.
Can ftp from the server but not to the server.

Logins are local or NIS with NFS home directories. Either behaves the same.

It is as if the port was "hung".
NPTY parameter setting is 500.

[Dirk Wiedemann]

Hello Sheri,

I had the same problem too times long time ago.
In the first case a co-worker used my ip adress for a other system which was not always up and running so if searched for the reason a while. Try another ip for your client.
In the second case I have cloned two HP-UX server in the same subnet with the same ignite tape. Surely I have changed the IP adresses of both systems to valid adresses but I didn't know that the mac-adress of the lan adapter is configured in the concerning configuration file and so I had two systems in one subnet with the same MAC-adress. *DOH*

hope this helps
Dirk

[harry d brown jr]

Sheri,

Like Dirk said, it sounds like duplicate IP's. The next time this happens, see if you can PING the host you are trying to ftp TO. Also, check your syslog log.

live free or die
harry

[Mihails Nikitins]

Some more troubleshooting ideas to think about.

Client systems having problem

- Are they the same all the time?
- Does ftp server deny _all_ ftp client connections (try to connect from some additional systems you haven't tried before) ?

FTP server

- Do you see any time correlation (e.g. problems happen at constant time, or last certain time)
- Do you see any higher system load when problems happen?
- Do you have appropriate patches installed?

Duplicate IP also may be an issue...

BR,
Mihail

[Sheri Gearhart]

Syslog shows no error messages on either the ftp server or ftp client.

I have now turned on inetd logging.

The IP addresses are NOT duplicate IPs.
I have verified this.

The server can be pinged.
In fact, you can log in to the server with rexec which uses inetd daemon.

[Kellogg Unix Team]

Are you using IPv6 ? I observed similar behaviour while installing wu-ftp on a solaris box with IPv6 turned on. Is the server HP or Sun ? :-)

...Manjeet

[Rory R Hammond]

I have seen similar problems. But I had clues in the syslog.
But your syslogd.conf file might be configured differntly.

npty is not the only setting to look at.
nstrpty was the culprit on 10.2
nstrtel was the culprit on
11.11i

He is test to try.
At one site, my nstrtel was set at the default of 60.

"who |wc" showed 58 login.

I recursively telneted to localhost, until I reached that limit.
I bet your logins are failing at peak times of the day, when you have reached you kernel limits

[Sheri Gearhart]

I am using IPV4 on all systems (Solaris or HP).

This server is an HP Superdome w/ 11i.

Rory, thanks for the info.
nstrtel = 200
nstrpty = 60

[Shannon Petry]

First, check for a machine with duplicate IP's and macs.
arp -a from a client which can not connect, and look at this compared to the output of lanscan for MACS.
For duplicate IP's check the network logs with
netfmt /var/adm/nettl.LOG00 |more

Next, check resolution on the client side. A while back I had a bunch of window$ users who were not able to connect to my SUN nor any HP's. There was a misconfigured WINS server, and DHCP server causing all kinds of problems.


Lastly is check networking equipment to make sure that equipment is not failing/overloading.

Regards,
Shannon