Lustre and HPC configuration

I have an HPC cluster with 22 nodes, and one head node as a master running Rocks Cluster OS (which is based on CentOS). The nodes and master communicate with private network (10.10.0.0/16). And we ssh to server with routed public network (192.168.xxx.xxx/24) and this network are not routed to the worker nodes. Now our data has reach it's limit, we can't add anymore disk to the master. Now we want to build a Lustre cluster consisting of 2 OSS and one MDS. My question is... Do we have to connect the Lustre OSS, and MDS to the same network with the HPC nodes (10.10.0.0/16), so that the nodes can mount our new LustreFS as Lustre clients? Or we can just mount the Lustre clients on the master node, and share the Lustre trough NFS for the HPC worker nodes? We will have other Lustre client outside HPC environment, so we will configure the Lustre on 192.168.xxx.xxx/24. Any suggestion?