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I'm using VirtualBox on Windows 8.1 (host) to run Ubuntu 13.10 as a guest.

Yesterday, I was able to log in using SSH/SFTP/FTP from the host to the guest without any problems, it was really fast.

A few days ago, I uninstalled some apps and installed a few updates on windows (the host) and I am now having troubles when I try to connect by SSH or FTP. The first request takes about 5 or 10 seconds. Any idea why this would be happening?

I've tried a few things already: - Re-install VirtualBox - Disable Firewall on both, host and guest. - Disable Dinwdows Defender.

Using Filezilla in Debug mode:

Status: Connecting to
Trace:  Going to execute "C:\Program Files (x86)\FileZilla FTP Client\fzsftp.exe"
Response:   fzSftp started
Trace:  CSftpControlSocket::ConnectParseResponse(fzSftp started)
Trace:  CSftpControlSocket::SendNextCommand()
Trace:  CSftpControlSocket::ConnectSend()
Command:    open "" 22
Trace:  Looking up host ""
Trace:  Connecting to port 22
Trace:  Server version: SSH-2.0-OpenSSH_6.2p2 Ubuntu-6ubuntu0.1
Trace:  Using SSH protocol version 2
Trace:  We claim version: SSH-2.0-PuTTY_Local:_Aug__7_2013_21:25:06
Trace:  Doing Diffie-Hellman group exchange
Trace:  Doing Diffie-Hellman key exchange with hash SHA-256
Trace:  Host key fingerprint is:
Trace:  ssh-rsa 2048 a6:28:76:90:89:f5:94:21:a1:44:f7:ac:53:d1:6d:07
Trace:  Initialised AES-256 SDCTR client->server encryption
Trace:  Initialised HMAC-SHA1 client->server MAC algorithm
Trace:  Initialised AES-256 SDCTR server->client encryption
Trace:  Initialised HMAC-SHA1 server->client MAC algorithm
Command:    Pass: ********
Trace:  Sent password
Trace:  Access granted
Trace:  Opened channel for session
Trace:  Started a shell/command
Status: Connected to
Trace:  CSftpControlSocket::ConnectParseResponse()
Trace:  CSftpControlSocket::ResetOperation(0)
Trace:  CControlSocket::ResetOperation(0)
Trace:  CFileZillaEnginePrivate::ResetOperation(0)
Status: Retrieving directory listing...
Trace:  CSftpControlSocket::SendNextCommand()
Trace:  CSftpControlSocket::ChangeDirSend()
Command:    pwd
Response:   Current directory is: "/home/marco"
Trace:  CSftpControlSocket::ResetOperation(0)
Trace:  CControlSocket::ResetOperation(0)
Trace:  CSftpControlSocket::ParseSubcommandResult(0)
Trace:  CSftpControlSocket::ListSubcommandResult()
Trace:    state = 1
Trace:  CSftpControlSocket::ResetOperation(0)
Trace:  CControlSocket::ResetOperation(0)
Status: Directory listing successful
Trace:  CFileZillaEnginePrivate::ResetOperation(0)

It gets stuck at this line for about 3 seconds; sometimes 5...

Trace:  Initialised HMAC-SHA1 server->client MAC algorithm


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You can use -vv option in ssh, which will show you the background processes while doing ssh. You will get to know the cause of slower performance, by looking at where the connection attempt going slower! Example: ssh -vv user@ – Uvais Ibrahim Feb 13 '14 at 4:34
@UvaisIbrahim thank you for checking in. I edited the question and included a log. I hope it helps. – Marco Florian Feb 20 '14 at 4:40
related to… – Kevin Panko Feb 24 '14 at 22:44
up vote 3 down vote accepted

I found out that it was a delay caused by the DNS lookup. I had to disable it:

Edit /etc/ssh/sshd_config and disable the property UseDNS:

UseDNS no
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