LinuxQuestions.org
Latest LQ Deal: Latest LQ Deals
Go Back   LinuxQuestions.org > Forums > Linux Forums > Linux - Networking
User Name
Password
Linux - Networking This forum is for any issue related to networks or networking.
Routing, network cards, OSI, etc. Anything is fair game.

Notices


Reply
  Search this Thread
Old 09-07-2016, 12:13 AM   #1
MrCervelo
LQ Newbie
 
Registered: Sep 2016
Posts: 2

Rep: Reputation: Disabled
Intermittent Network issue from Centos 6/7 to Debian - Not Physical Network


Hi All

I hope that this is the right area for this question. I'm experiencing a weird network issue with Centos 6 and 7. I am trying to connect to a Debian machine running Jira and Nagios via http and ssh and it times out. But, this is not a physical network issue as other machines (Windows) can connect to the same device with no issues. Additionally, if I run a VM (Windows 10) on the same machine, it works with no issues, and VMs running Centos 6 on Windows 10 host are experiencing the same timeout/connectivity issues.

To add even more fun to the mix, the problem is intermittent. Myself and another employee have been comparing notes, and sometimes it will work for him and not for me, and vice versa but more often than not, it will not work for either of us.

Ping and Telnet (even to port 22 and 80) work without an issue, but telnet, curl etc are all intermittent (reliably so, they all work, or they all fail).

Through another server, I was able to ssh to the destination server and I performed a tcpdump locally and on the server while I tried to ssh to it. The results were unexpected. Both showed traffic, so the data is getting through, but only the very first packet, after that both dumps show "TCP Retransmission".

I'm running out of ideas here, so any assistance is appreciated.
 
Old 09-08-2016, 08:40 AM   #2
MensaWater
LQ Guru
 
Registered: May 2005
Location: Atlanta Georgia USA
Distribution: Redhat (RHEL), CentOS, Fedora, CoreOS, Debian, FreeBSD, HP-UX, Solaris, SCO
Posts: 7,831
Blog Entries: 15

Rep: Reputation: 1669Reputation: 1669Reputation: 1669Reputation: 1669Reputation: 1669Reputation: 1669Reputation: 1669Reputation: 1669Reputation: 1669Reputation: 1669Reputation: 1669
Is it possible you have more than one machine inadvertently using the same IP?

How many NICs on the source CentOS system are configured? What is the default route set to when you look at "netstat -rn"? What is in your /etc/sysconfig/network-scripts/ifcfg-<nic> files?

CentOS6/7 use Network Manager so there may be things setup in the ifcfg files that are different as compared to what CentOS5 used.
 
Old 09-08-2016, 05:37 PM   #3
MrCervelo
LQ Newbie
 
Registered: Sep 2016
Posts: 2

Original Poster
Rep: Reputation: Disabled
Quote:
Originally Posted by MensaWater View Post
Is it possible you have more than one machine inadvertently using the same IP?
Unlikely, the issue is affecting multiple machines and it only seems to affect this particular device. I can bypass the issue by using an SSH tunnel to another device that then connects on port 80. I shouldn't be able to tunnel if I have an IP address conflict.

Quote:
Originally Posted by MensaWater View Post
How many NICs on the source CentOS system are configured?
I have 2 but other users only have a single NIC. However, only one NIC is actually connected to the network.

Quote:
Originally Posted by MensaWater View Post
What is the default route set to when you look at "netstat -rn"?
Code:
netstat -rn
Kernel IP routing table
Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface
0.0.0.0         192.168.111.22  0.0.0.0         UG        0 0          0 enp4s5
192.168.111.0   0.0.0.0         255.255.255.0   U         0 0          0 enp4s5
192.168.122.0   0.0.0.0         255.255.255.0   U         0 0          0 virbr0
Quote:
Originally Posted by MensaWater View Post
What is in your /etc/sysconfig/network-scripts/ifcfg-<nic> files?
Code:
cat /etc/sysconfig/network-scripts/ifcfg-enp4s5 
TYPE="Ethernet"
BOOTPROTO="dhcp"
DEFROUTE="yes"
IPV4_FAILURE_FATAL="no"
IPV6INIT=no
IPV6_AUTOCONF="yes"
IPV6_DEFROUTE="yes"
IPV6_PEERDNS="yes"
IPV6_PEERROUTES="yes"
IPV6_FAILURE_FATAL="no"
NAME="enp4s5"
UUID="23a26e53-1f0a-4548-a2b8-a29277f1cef2"
DEVICE="enp4s5"
ONBOOT="yes"
DNS1=192.168.111.22
DNS2=8.8.8.8
PEERDNS=no
PEERROUTES=yes
Thanks for thinking about this. It was less problematic yesterday but still affecting myself and another heavy user of this system.
 
  


Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is Off
HTML code is Off



Similar Threads
Thread Thread Starter Forum Replies Last Post
Issue with network on centos 7 sysmicuser Linux - Newbie 4 07-02-2016 02:51 AM
Network Namespaces - how to connect namespace to physical network circumventing VPN cricketbat Linux - Networking 1 01-03-2016 08:06 AM
CentOS 6 - KVM - Physical host losing network connectivity after Bridge configuration gkulkarni Linux - Virtualization and Cloud 10 10-27-2013 05:41 PM
HP Network Printer Issue on CentOS 5.3 x86_64 GenePoole59 Linux - Software 1 07-01-2011 11:50 AM
Network issue KVM host centos michaelux Linux - Virtualization and Cloud 3 06-06-2010 12:51 AM

LinuxQuestions.org > Forums > Linux Forums > Linux - Networking

All times are GMT -5. The time now is 08:32 AM.

Main Menu
Advertisement
My LQ
Write for LQ
LinuxQuestions.org is looking for people interested in writing Editorials, Articles, Reviews, and more. If you'd like to contribute content, let us know.
Main Menu
Syndicate
RSS1  Latest Threads
RSS1  LQ News
Twitter: @linuxquestions
Open Source Consulting | Domain Registration