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Diagnosing network corruption
Some network card models require firmware upgrades from the vendor to work reliably under load, or when
certain optimizations are turned on. If you are seeing corrupted traffic to VMs, then you should first try to obtain
the latest recommended firmware from your vendor and apply a BIOS update.
If the problem still persists, then you can use the CLI to disable receive / transmit offload optimizations on the
physical interface.
Warning:
Disabling receive / transmit offload optimizations can result in a performance loss and / or
increased CPU usage.
First, determine the UUID of the physical interface. You can filter on the device field as follows:
xe pif-list device=eth0
Next, set the following parameter on the PIF to disable TX offload:
xe pif-param-set uuid=<pif_uuid> other-config:ethtool-tx=off
Finally, re-plug the PIF or reboot the host for the change to take effect.
Recovering from a bad network configuration
In some cases it is possible to render networking unusable by creating an incorrect configuration. This is
particularly true when attempting to make network configuration changes on a member XenServer host.
If a loss of networking occurs, the following notes may be useful in recovering and regaining network connectivity:
• Citrix recommends that you ensure networking configuration is set up correctly before creating a resource
pool, as it is usually easier to recover from a bad configuration in a non-pooled state.
• You can run the host-management-reconfigure command from any host in the pool. This is because you specify
the PIF UUID for the NIC that you want to affect.
• The host-management-disable command affects the XenServer host on which it is run so it is not suitable for
use on one host in a pool to change the configuration of another. Run this command directly on the console
of the XenServer host to be affected, or use the xe -s, -u, and -pw remote connection options.
• When the xapi service starts, it applies configurations to the primary management interface first. The name
of the primary management interface is saved in the /etc/xensource-inventory file. In extreme cases,
you can stop the xapi service by running service xapi stop at the console, edit the inventory file to set the
primary management interface to a safe default, and then ensure that the ifcfg files in /etc/sysconfig/
network-scripts have correct configurations for a minimal network configuration (including one interface
and one bridge; for example, eth0 on the xenbr0 bridge).