Lubuntu 16.10 ESXi 6.5 extreme network performance problems

[itmv2]

I've had a Lubuntu 16.10 server running as a guest VM on an ESXi 6.5 (free edition) host for a couple of weeks. Until last night it was running fine, but today it is having major problems with both inbound and outbound network connections:
- Timeouts accessing web resources on both LAN and WAN (e.g. BBC website or Logitech Media Server web GUI running on the LAN). Internal sites can sometimes be accessed, but not for long. External sites pretty much always time out
- No inbound connections possible to VNC server or mediawiki site on the Lubuntu machine from other machines on the LAN (was working fine until this morning). The mediawiki site is up and running, and can be accessed from the Lubuntu machine itself. I did fleetingly manage to access a couple of pages from the mediawiki site from another machine on the LAN, but then it stopped responding, so it seems to be a performance rather than connectivity issue (and it was connecting fine until this morning)

- Unable to download software packages in Synaptic package manager - the installer virtually hangs trying to download a package.

There is one other VM running on the same ESXi host - a Windows machine. This has absolutely no network issues (inbound or outbound), so I assume that the networking hardware is fine on the host. I've tried shutting down the other VM but it didn't help. I've also tried rebooting the router/gateway and the Lubuntu server.

I originally had the network interface configured as E1000. I've tried changing it to VMXNET 3 but it made no difference.

Can anyone advise on how I can diagnose this issue? I'm an ESXi and Linux novice so please bear with me!

Last edited by ianmanning; 19 Minutes Ago at 10:59 AM.

[montythreecard]

Ok, first of all, do not, DO NOT use the VMXNET 3 network card driver if you are running the current release of ESXi.  There is some weird bug in the newest versions (right up to the current release, build 7388607), that freezes when pulling data down from the network card (See bug 191201 – Randomly freezes due to VMXNET3 ).    For all VMs until this bug is addressed, use the e1000 driver for Ubuntu VMs, and the e1000e driver for Windows 8, 8.1, and Windows 10 VMs.
Then check your /etc/network/interfaces file to make sure any cards match the ports if you change the driver.  (Full disclosure, we run Ubuntu, not Lubuntu).  Ubuntu 16 changed the assignments from eth0 and eth1 to ens numbers that change DEPENDING ON THE DRIVER/MAC ADDRESS YOU ARE USING.  So, if you switched drivers, go into the console ssh client, and do "ip link" and see what address the card(s) are living at, and adjust the interfaces file accordingly.  For example, our configuration looks like this:

auto ens36

iface ens36 inet static

        address INTERNAL IP HERE

        netmask 255.255.255.0

        gateway PATH TO GATEWAY

        dns-nameservers 8.8.8.8 8.8.4.4

For the e1000 driver.  This is changed from the VMXNET 3 address, ens160 or ens192 (for example). 

You can also check your actual network connectivity by turning on the ESXi SSH client in the host (Host->Actions->Services->Enable Secure Shell SSH), and checking your connectivity there by SSHing in, and trying to connect to the 'net, and downloading a file > about 10MB.  Remember to turn it off when you are done, or reboot ESXi afterward.  If you can download fine there, then it is the virtual networking that is an issue (and probably the driver/assignments).

Good luck!