Serious latency over SSH: CentOS 6.3 VNC is fine, no visible I/O bottlenecks

Question

This is not an issue about logging in via SSH, this is a lag during typing input and receiving output while connected to a server via SSH. I tested the speed of the commands using the time command and see that they are running normally but that input to and output from the terminal is lagging. VNC is fast. Pinging remote servers from this server shows normal response times. SSH sessions to other machines from my machine seem fine. openssh-server 5.3p1-84.1.el6

The fact that VNC is fast should be enough, but for info, RAM is fine, no swapping is occurring, CPU usage is low, ethtool shows network at 1 Gigabit.

I should mention that this is a virtual machine running on KVM, so when I connect to VNC, I actually connect to the host at port 5905. — , Apr 17 '13 at 18:35

score 1 · Answer 1 · answered Apr 18 '13 at 14:56

1

I am a knucklehead! I had duplicate MAC addresses on another VM. Changing the MAC to be unique instantly resolved the issue.

answered Apr 18 '13 at 14:56

Good to know. Next time should use arping – maxxvw Apr 19 '13 at 16:13

score 0 · Accepted Answer · answered Apr 17 '13 at 18:01

0

You should at your lost packets rate via a ping command. Ssh doesn't like it at all

answered Apr 17 '13 at 18:01

maxxvw

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There are no dropped packets or errors showing up in ifconfig. – Apr 17 '13 at 18:08
I was not talking about that but lost ones when you ping your server – maxxvw Apr 17 '13 at 19:53
You were right, pings are getting dropped when I ping this server. How do I resolve? – Apr 18 '13 at 12:50
You should delete question... – maxxvw Apr 18 '13 at 19:00
I can't delete it because it has answers. – Apr 18 '13 at 21:13
I dont want to accept my own answer, but the issue was dupe MAC address. – Apr 19 '13 at 15:28

Serious latency over SSH: CentOS 6.3 VNC is fine, no visible I/O bottlenecks

2 Answers2