User Manual

Rev 1.8.2
Mellanox Technologies
19
For VGT mode, VLANs need to be configured in the installed guest operating system. This procedure
may vary for different operating systems. See your guest operating system manual on VLAN configu-
ration.
In addition, for each new interface created within the virtual machine, at least one packet should be
transmitted. For example:
Create a new interface (e.g., <eth1>) with IP address <ip1>.
To guarantee that a packet is transmitted from the new interface, run:
arping -I <eth1> <ip1> -c 1
• Virtual Switch Configuration
For VST mode, the virtual switch using an InfiniBand uplink needs to be configured. For further
information, see the ESXi Server 3 Configuration Guide and ESXi Server 3 802.1Q VLAN Solutions
documents.
5.2.4 Maximum Transmit Unit (MTU) Configuration
On VMware ESXi Server machines, the MTU is set to 1500 bytes by default. IPoIB supports
larger values and allows Jumbo Frames (JF) traffic up to 4052 bytes on VI3 and 4092 bytes on
vSphere 5. The maximum value of JF supported by the InfiniBand device is:
• 2044 bytes for the InfiniHost III family
• 4052 / 4092 bytes for ConnectX® IB family (vSphere 5)
It is the administrator's responsibility to make sure that all the machines in the network support
and work with the same MTU value. For operating systems other than VMware ESXi Server, the
default value is set to 2044 bytes.
The procedure for changing the MTU may vary, depending on the OS. For example, to change it
to 1500 bytes:
• On Linux - if the IPoIB interface is named ib0, run:
ifconfig ib0 mtu 1500
• On Microsoft® Windows - execute the following steps:
a. Open "Network Connections"
b. Select the IPoIB adapter and right click on it
c. Select "Properties"
d. Press "Configure" and then go to the "Advanced" tab
e. Select the payload MTU size and change it to 1500
f. Make sure that the firmware of the HCAs and the switches supports the MTU you wish to set.
g. Configure your Subnet Manager (SM) to set the MTU value in the configuration file. The SM configuration
for MTU value is per Partition Key (PKey).
For example, to enable 4K MTUs on a default PKey using the OpenSM SM6, log into the Linux
machine (running OpenSM) and perform the following commands:
h. Edit the file:
Running a datagram IPoIB MTU of 4092 requires that the InfiniBand MTU is set to 4k.