Network Performance Issues on Windows 7 – Troubleshooting Guide

networkingrdcsshwindows 7

One of my machines has started to get serious networking issues. This all started to happen suddenly although I am not aware of any specific changes made to the machine. It is running Windows 7.

Some of the symptoms that was not a problem before:

ssh into the machine rarely works and when it does it might stop after some minute
rdesktop to this machine shows similar symptoms as ssh, if you manage to get in it freezes after a short time, but usually you do not get in at all.
nmap shows: Note: Host seems down. If it is really up, but blocking our ping probes, try -PN. This worked fine before.

However connecting with vnc has no problems at all.

Googling around I have tried some tips, none working so far such as turning off RDC (remote differential compression), turning off firewall, turning off antivirus, turning off network auto tuning.

How can I find out what the problem is ?

Best Answer

Before you say "network" let's understand what LAYER you're talking about here.

If it's truly a "networking" problem its going to be layer 3 and below.

So... check the following:

Layer 1: Frayed or kinked cable? If you have a managed switch can you see any physical errors on the port utilized by the client? Is the NIC linking at half or full duplex, 10 or 100 or 1000?

Layer 2: Thrown on Wireshark and lookout for any duplicate MAC addresses jibber jabbering back and forth.

Layer 3: Is it receiving a valid address not shared by any other peer on the network?

As for the OS itself... check the usual culprits:

3rd party and OS firewalls fighting each other.
Protocols you're not using yet, like IPv6, uncheck it.
bad DNS configuration
Did you set the connected "network" as Work/Home or Public?

Troubleshoot some more.

Related Solutions

Ssh hangs on “Last login” line

Login using ssh -vvv and see what debug info shows up. This is odd in that the last login line is usually after the ssh session is setup. Also check your /var/log/{messages,auth,daemon} and whatever else is relevant.

Are your drives full? Is something unexpected going on with configuration? I know you didn't change it, but maybe something was compromised?

Ubuntu – SSH by key incredibly slow

Do you have the same troubles by password authentication, or this is really related to key authentication?

You client may provide proper DNS resolution, but it is your server which will try anyway to perform a reverse-lookup from your IP address; this may explain the delay, as @kasperd says. But from experience, this does not exceed a few seconds.

Does SSH succeeds in authentication finally? If so, it really looks like a DNS problem. Try if your configuration/administrator permits so adding your IP/hostname into the server's /etc/hosts. This will bypass the DNS resolution on server side. If you won't configure your DNS to provide proper reverse-lookup on server side for the client, useDNS no is, as @kasperd says, to be put on the /etc/ssh/sshd_config of the server.

If your administrator won't do this, there is nothing more your can do.

EDIT: There is absolutely no way KDE/Unity or any desktop manager could result in this slowdown. I would be amazingly surprised this is the case. However, the fact you need to provide ssh-add to use your keys is interesting. This command is used to make your authentication agent to remember the passphrases you tipped for your keys. To specify key to be used, either do it by command line, or in your ~/.ssh/config file:

# in your command line:
ssh -i /path/to/your/private/key user@host

# or in your /home/$user/.ssh/config file:
# (on command line later, simply use ssh user@host or ssh host if
# user locally and remotely are the same
Host $myhost
    IdentityFile /path/to/your/private/key
    IdentitiesOnly yes

Best Answer

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Ssh hangs on “Last login” line

Ubuntu – SSH by key incredibly slow

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