Private Interconnect: Should any nodes other than RAC nodes have one?

Question

The contractors that set up our four-node production 10g RAC (and a standalone development server) also assigned private interconnect addresses to 2 Apache/ApEx servers and a standalone development database server.
There are service names in the tnsnames.ora on all servers in our infrastructure referencing these private interconnects- even the non-rac member servers. The nics on these servers are not bound for failover with the nics bound to the public/VIP addresses. These nics are isolated on their own switch.
Could this configuration be related to lost heartbeats or voting disk errors? We experience rac node expulsions and even arbitrary bounces (reboots!) of all the rac nodes.

Answer 1

I do not have access to the contractors. . . .can only look at what they have left behind and try to figure out their intention. . .
I am reading the Ault/Tumha book Oracle 10g Grid and Real Application Clusters and looking through our own settings and config files and learning srvctl and crsctl commands from their examples. Also googling and OTN searching through the library full of documentation. . .
I still have yet to figure out if the private interconnect spoken about so frequently in cluster configuration documents are the binding to the set of node.vip address specifications in the tnsnames.ora (bound the the first eth adaptor along with the public ip addresses for the nodes) or the binding on the second eth adaptor to the node.prv addresses not found in the local pfile, in the tnsnames.ora, or the listener.ora (but found at the operating system level in the ifconfig). If the node.prv addresses are not the private interconnect then can anyone tell me that they are for?