About RAC add Node on 11.2.0.3

 Dear All,

There are 2 nodes of 11.2.0.3 PSU6 in RAC on AIX for now. And we are going to add 2 more nodes into the RAC. 

But we got some concern on that :

1, the new nodes' machines are located next to the existed two, that means the new two machines have to use a different switcher which next to the old one on private network .

even if the network team could create a vlan for the new ones, but it is normal for private IP uesage? Is the cache in network would affect the private network?

2,if the existed two nodes is 11.2.0.3 PSU6, is that possible that the new 2 installed with 11.2.0.3 PSU9 ? I mean that  whether  11.2.0.3 PSU9 nodes  could add into 11.2.0.3 PSU6 RAC?