This is a heads up on an issue I ran into some time ago upgrading to VMware ESXi 4.0 Update 1 on an IBM System x3850.  Granted, it’s an aging hardware platform and fast becoming a dated issue, nonetheless this information may help someone out of a late night or weekend fiasco.

Shortly after the upgrade, VMs began experiencing intermittent losses in network connectivity.  Tied to the problem, the following error was revealed in the ESXi log files:

WARNING: LinNet: netdev_watchdog: NETDEV WATCHDOG: vmnic7: transmit timed out

The root cause turned out to be a known issue with the e1000e driver on ESXi 4.0u1 and the IBM x3850.  The issue is documented well in VMware KB Article 1010313 (Intel 82571 NICs intermittently lose connectivity with ESX 4.x).  The KB article was updated last April and appears to still be giving VMware fits as it has spread to vSphere 4.1.  According to the KB article:

This issue may occur if the Message Signaled Interrupt (MSI) mode is enabled for the e1000e driver and this mode is not supported in a server platform. This driver supports these three interrupt modes:

• 0.Legacy
• 1.MSI
• 2.MSI-X

ESX 4.0 added support for Message Signaled Interrupts in network and storage drivers. The default interrupt mode for the e1000e driver under ESX 4.x is MSI (1).

The workaround according to the KB article is to configure the e1000e driver to use Legacy (0) Interrupt mode (thus disabling MSI mode) by performing the following:

1. Open a console to the ESX or ESXi host.
2. To configure the e1000e module option IntMode and use Legacy (0) interrupts for a 4-port NIC, run the command:
   • esxcfg-module -s IntMode=0,0,0,0 e1000e
   • Note: A mode number must be specified for each NIC port. In case of 2 quad port NICs, specify the mode 0 for all 8 ports with the command:esxcfg-module -s IntMode=0,0,0,0,0,0,0,0 e1000e
3. On ESX host, run this command to rebuild initrd:
   • esxcfg-boot -b
   • Note: This step is not applicable to ESXi hosts.
4. Reboot the ESX/ESXi host for the changes to take effect.

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