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Old 12-05-2017, 01:08 PM   #1
cmdrkyle
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Multiple CentOS office servers get no return TCP packets when sending to hosted CentOS server


Hello,

I have 3 CentOS severs that I have tried in our Orlando, Florida office that get connection timeouts to our hosted dedicated CentOS server in Tampa, Florida. UDP works and TCP packets get received, but are either dropped or no return message sent. I'm in Michigan so a few tests aren't super easy. I have SSH access to all machines. Hosted machine has cPanel. Our other offices can connect just fine. Multiple ports affected, including: 80, 21, 22, 3306.

I've tried about a hundred things and I'll try to list some here. Thanks!

- Rebooted all servers
- Took office server out from behind hardware firewall and turned off software firewall on hosted server
- Changed public IP address for office by switching to backup ISP
- Changed firewall to more standard 1400 MTU
- Wireshark shows sftp packet arrives, and a TCP Retransmission seconds later
- Windows computers on the same network work
- The hosted server can connect to the office server (opposite direction)
- traceroute works, tcptraceroute stops at the hosted server
- Can send data with nc over udp, but not tcp
- Can connected to other hosted server at same provider
- SELinux is not running
- Tried with multiple FQDNs and multiple IPs that the server has

Any thoughts or ideas would be greatly apreciated! Thanks!

Last edited by cmdrkyle; 12-05-2017 at 04:16 PM. Reason: spelling
 
Old 12-05-2017, 03:29 PM   #2
cmdrkyle
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To update this, one of the 3 computers can now connect for reasons unknown. I haven't changed anything on that machine. I disabled the cPHulk Brute Force Protection and turned it back on. That shouldn't have made a difference though or it should have fixed it for all 3.
 
Old 12-05-2017, 09:37 PM   #3
frankbell
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Is it possible that the firewalls are disallowing incoming ICMP requests (that is, set not to respond to pings)?

See man icmp for more.
 
Old 12-06-2017, 09:55 AM   #4
cmdrkyle
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Quote:
Originally Posted by frankbell View Post
Is it possible that the firewalls are disallowing incoming ICMP requests (that is, set not to respond to pings)?

See man icmp for more.
Pings and traceroute is getting through, TCP traceroute is not though (or really getting received, but dropped or no reply)

Thanks!
 
  


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