Different Frame Size For Subnets On The Same Interface

Hello,

I have a customer with a 3-node Isilon cluster. It has two pools on different subnets on the same network interfaces. "Client_Subnet" is uses for Windows CIFS Clients. "NFS_Subnet" is used for vSphere NFS Datastores. Both subnets use the same 10gigE interfaces. Cluster is on OneFS 7.1.1

Subnet #1

Name: Client_Subnet

Subnet: 192.168.1.0

Netmask: 255.255.255.0

MTU: 1500

Gateway 192.168.1.254

with pool

Client_Pool

IP-Range: 192.168.1.11 - 192.168.1.13

Access Zone: System

Pool Members: 10gige-agg1 (Node 1-3)

Subnet #2

Name: NFS_Subnet

Subnet: 192.168.2.0

Netmask: 255.255.255.0

MTU: 1500

with pool

Client_Pool

IP-Range: 192.168.2.11 - 192.168.2.13

Access Zone: System

Pool Members: 10gige-agg1 (Node 1-3)

The customer wants to use jumbo frames on the NFS subnet. Regarding to Isilon OneFS CLI Administration Guide MTU can be modified on a subnet base using "isi networks modify".

When trying to set the MTU for "NFS_Subnet" to 9000 I get the following errors:

isilon1-rv-1# isi networks modify subnet --name=NFS_Subnet --mtu=9000

Modifying subnet 'NFS_Subnet':

!! modify subnet command failed: The following interface would be

!! assigned to subnets with conflicting MTUs: 1:10gige-agg-1.  Use the

!! --force option to override this warning. Configuration will not be

!! saved.

How is ist possible to run two different subnets on the same interfaces, one running with MTU 9000 and the other with MTU 1500?

Best regards

Robert Spiess