Question

Can jumbo frames (MTU 9000) be configured on a HMC?

Cause

 

RMC communications between the HMC and LPARs using jumbo frames is failing.

 

Answer

 

The 7042 series of HMCs do come with Gigabit Ethernet adapters that do support jumbo frames.  You will need and HMC code level of v7r3.5 or later to get support for jumbo frames.  

If AIX LPARs are using jumbo frames on their network interface that communicate via RMC with the HMC then jumbo frames would need to be configured on the HMC for applications such as dynamic logical partitioning (DLPAR) and partition mobility (LPM) to work properly.  The command to change the HMC's public network interface is chhmc.  Following is an example.

chhmc -c network -s modify -i eth1 --jumboframe on

Note: example above is for configuring eth1.  Use the appropriate adapter interface when configuring your HMC.

netstat -in is used to verify if MTU size changed from 1500 to 9000.

The network (routers and switches) between the HMC and the LPAR will also need to be configured to support Jumbo frames if RMC is to work properly.