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Old 04-22-2013, 02:57 AM   #1
sunnysthakur
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Remote Linux server not accessible from same gateway after somedays


Hello,

We are working on Client's remote server and accessing the same from putty from our office.
Now from last 1 month we are facing an issue of inaccessibility of servers from same gateway we configured on our Desktop.

However some machines are accessing the same remote server from same gateway some are not and having error "Server unexpectedly closed network connection"

Then user switched to another gateway which we have as backup. But after some days again remote server stop accessible from this new gateway.

We have Gateways on Linux servers.

I am not able to figure out this issue and need help on the same.

Thanks in advance...
 
Old 04-22-2013, 10:33 AM   #2
Sigg3.net
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Are you using SSH to access the machines? What GNU/Linux OS is there on the remote machine(s) and gateways?
It's a little hard to troubleshoot without specifics
 
Old 04-23-2013, 12:49 AM   #3
lleb
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when you say gateway are you referring to your local router or are you talking something different.

ex:

IP: 192.168.1.100
subnet: 255.255.255.0
gateway: 192.168.1.1 were this is your local router facing the outside world performing your local NAT.

on the remote system you are connecting to are you running any form of firewall, IP filtering, or SELinux?

these are in addition to what Sigg3.net asked.
 
Old 04-25-2013, 04:49 AM   #4
sunnysthakur
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Yes i am usinf ssh to access the remote machine and CentOS 6.x OS is running on the remote server. I also check the logs on the remote machine [Access this from other machine as this is accessible from some machines only] and didn't find any thing related to this issue, traceroute to my gateway is working fine from the remote machine.
 
Old 04-25-2013, 04:52 AM   #5
sunnysthakur
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Yes i am referring to my local gateway and we have setup a NAT to access the internet from this server with in the office.

Currently i checked and firewall/Selinux linux is disabled on remote server.

Any other way to figure this out that this issue is from our end or remote end.
 
Old 04-25-2013, 03:25 PM   #6
Sigg3.net
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Can other machines at the same site as the CentOS server ssh into it when you cannot from your site?

But since traceroute to your gateway from the CentOS server works fine _when_ this is happening (??) it would probably be some problem with your gateway and/or the Windows machine (I infer Windows, since you use Putty). Is it a custom gateway or off-the-shelf hardware?

Putty itself is pretty bulletproof. Have you added it to Windows' own security hoops (firewall, AV software whitelist etc)?
 
Old 04-25-2013, 03:53 PM   #7
u2013
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Quote:
Originally Posted by sunnysthakur View Post
Yes i am referring to my local gateway and we have setup a NAT to access the internet from this server with in the office.

Currently i checked and firewall/Selinux linux is disabled on remote server.

Any other way to figure this out that this issue is from our end or remote end.
UPDATE 1.
Oops. I read the word "somedays" as "sundays" and did not read completely. I guess i need to enlarge the font more. I removed my post since your gateway is via linux server, which I assume the linux is setup as a router.

UPDATE 2.
Is it possible you are having an IPA conflict?
Meaning, that at one point or another one machine gets assigned (dynamic) or is assigned (static) the IPA that another machine has? If so, then what you describe could happen I believe.

Last edited by u2013; 04-25-2013 at 04:06 PM. Reason: misunderstood.
 
Old 04-26-2013, 12:10 AM   #8
chrism01
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One possibility is eg fail2ban running on the remote.
If it gets hit too often, it'll block the incoming IP.

Another is pam_tally for too many failed logins (maybe).

There could be a rogue process trying to connect, causing one or other of the above.
 
  


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