ftp sometimes doesn't work

[Fern H2O]

Hello All,

Here's the Overview. I have 2 Itanium servers, 11.23, production. 95% of times everything works good, but sometimes outgoing ftp from these servers do not work. I was alerted of this issue and while outgoing ftp doesn't work, incoming ftp connections do work. But after a couple of mins, everything goes back to normal.

I don't see anything weird in syslog..
Does anyone have an idea of what's going on??

[Fern H2O]

Just in case, here's what happens. Lets say hostnameA is the one in question here...

hostnameA: ftp to hostnameB... just hangs
hostnameB: ftp to hostnameA... works

[Michael Steele_2]

hi

Do you have a 'ftp' proxy server? Are you going through a fire wall? I believe 'ftp' uses both ports 20 and 21, one for data transfer and the other for control.

Next time you see the problem, test the ports.

telnet ip 20
telnet ip 21

You should see a CONNECTION ESTABLISH message. This is your verification that all is well.

If the telnet hangs forever, then the port is blocked.

And of course, try both the hostname and the ip address when testing, in order to verify the DNS resolver.

[Tingli]

Apart from network, how about the disk i/o in the receiving side?

[Fern H2O]

Thanks Michael for your response but I think you misunderstood my problem.

ServerA isn't able to ftp anywhere
but every other server is able to ftp TO ServerA.

So basically every server can connect to ServerA using ftp w/o a problem.
But Server A cannot ftp elsewhere.

Now, like I said this isn't a constant problem but it has happened twice today for about a 5 mins period. Usually ServerA has no problem ftp'ing to wherever. but in some cases it seems like it hangs..

Firewall isn't an issue, since all the servers are on the same network.

And I don't think its a network issue, since everything else keep running status quo.

[Fern H2O]

Also,

I don't think its possible to telnet to ftp-data port 20... only 21..

[Michael Steele_2]

Hi

If you refer to this link you'll see that ftp uses both 20 and 21.

http://www.iana.org/assignments/port-numbers

Why don't you check you services file and inetd.conf file and see if its turned off? Also verify the ftp arguements in inetd.conf to be the same as the other boxes.

[Fern H2O]

When its having this issue it doesn't matter what server i try to ftp to... it just seems to hang...

[Michael Steele_2]

A) "...ServerA isn't able to ftp anywhere
but every other server is able to ftp TO ServerA...."

B) "...So basically every server can connect to ServerA using ftp w/o a problem.
But Server A cannot ftp elsewhere...."

C) Which you just posted "... When its having this issue it doesn't matter what server i try to ftp to... it just seems to hang..."

You are contradicting yourself and the problem and need to focus.

If it is affecting every server then it is probably a firewall issue and your port is blocked!!!

-but-

That it only happens for 5 minutes at a time suggests a big file transfer that in the giga bytes size that you should be able to cross reference the time stamp with.

Does your business make any cron auto exectued file transfers?

Are your sys admins syncing up with a remote site, perhaps with Oracle database log files?

[Fern H2O]

Hello,

Thanks for the feedback Michael.

It seems the issue only arises when mem usage is 100% and swap is really high.

And i noticed that when ftp looks like it hangs, if I wait about a minute it would work. So, it seems its a lack of resource issue.

Thanks anyways,