Dell EMC S4048T-switch MTU Sizes – Configure Jumbo Frames for NIC cards in the Linux-based Dell EMC vSAN Ready Node OS servers.

Summary –

We were doing the implementation of DELL HCI in large organization. Started implementation of Dell EMC vSAN ready node. Dell’s Server were connected with Dell Switch S4048T. Physically we have 5 node and two Dell switch.

Now Problem is that while installing VCenter in one of the node and then other node to move in cluster where Vcenter installed. However, after some time VCenter is not responding. We went through the usual troubleshooting routine and discussed with our superior team whether it was either a problem with the ESX hosts (running latest update ESX 6.7) or something to do with the network configuration.

We have set Jumbo frame at both side Switch and Server side. We have set 9000 MTU sixe in both side.

Problem identified during the ping from server.

Solution Work –

Server – Dell EMC VSAN Ready Node R740xd

Switch – Dell Networking S4048T-ON

Perform the following steps, for all the NIC cards in the VSAN NODE OS system-


  1. Run the ifconfig command to get the NIC information.
  2. Depending on the OS, run the command:
Operating System Command
RHEL/CentOS Edit /etc/sysconfig/network-scripts/ifcfg- <NIC_NAME>
SLES Edit /etc/sysconfig/network/ifcfg-<NIC_NAME>
  • Add parameter mtu=9000 to the file.
  • To apply the changes, type: service network restart
  • Execute ifconfig again to verify that the settings was changed.
  • To test the command,

$ping –M do –s 8972 <DESTINATION_IP_ADDRESS> 

If MTU setting is correct then you were able to ping otherwise not if MY mismatch.

However, in our case we are not able to ping on frame size 9872 because JUMBO frame was mismatch. We have set 9000 MTU at both side switch and Server. You can set 9000 MTU at server side but have to set higher MTU at switch side.

MTU calculate as 9*1024 = 9216.

Login in DELL SWITCH 4048T and set the MTU on connected interface.

console# configure

console(config)# interface range ethernet all  (Take you interface name which was connected with node)

console(config-if)# mtu 9216

console(config-if)# exit

console(config)# exit

console# copy running-config startup-config

console# exit

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