Cannot SSH into a VMWare Guest.

Posted on by Arun PC

Note:- This article is technical.May not be useful for people NOT working with virtual machines

Scenario

The Host machine runs Vmware Server on Linux and the guest also runs Linux virtual machine.

Problem Summary
When trying to ssh from the Host Linux box into the guest Linux box, it just stays with the command and fails to execute or throw an error.It just remains like this.

ssh user@192.168.X.Y
<nothing happens after this.No error thrown>

The logs(/var/log/ssh or /var/log/auth.log) also doesnt show anything useful.

Test
Host machine can ssh into other machines in the network.

Host machine cannot ssh into any Vms it carries.

Host machine can PING to all Vms aswell as the other machines on the network.

Diagnosis
The problem is with the ethernet card settings. We need to tune the ethernet card settings with a tool called ethtool.(see MAN ethtool pages for various options).

By executing the below given command we disable some kernel modules like Rx checksum and scatter gather which solves the problem.

ethtool -K eth0 sg off rx off tx off tso off

Hope some of you found it useful.

Thanks,

Arun.PC

Published by Arun PC

Father of two beautiful children, husband to a patient wife. Loves good a book, a pint of beer and good tech. Follow me https://twitter.com/arun_p_c

8 thoughts on “Cannot SSH into a VMWare Guest.”

  1. Thanks a bunch. I had narrowed the problem down to an interaction of the VMWare and the kernel’s networking code. Your ethtool command resolved the problem perfectly.

    Here’s a virtual beer/coffee 🙂

    Rob

    1. Open your device manager, open your properties for your NIC, select the advanced tab and turn off all instances of checksum offloading. This will have the same effect.

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