Concept behind IP Network Addressing in crs installation, rac

As yesterday i was installation CRS and i got stuck on Network Configuration Screen, where i have to fill the Public, Virtual & Private network IPs... i was getting following error i.e.

You must enter unique values for the public node name, the private node name and the virtual hostname for all nodes in the cluster. The name, YOUR-HOSTNAME , that you entered is being used by more than once for the same node.

AND

The virtual hostname(s), YOUR-HOSTNAME, you have specified appears to be already assigned to another system on the network. Please ensure that the virtual hostname(s) that you use for each of the nodes in the cluster are not in use currently.

after reading the ORACLE official documentation and testing the provided machine's configuration i found that, my installation server had name resolution problem, firstly our DNS was resolving hostname on wrong IP and later when they changed it to resolve from /etc/hosts it was unable to resolve from this file...anyhow later with investigation i was able to give a brief idea that how CRS IP Network Configuration should look like, its simple ! here it is:

Concept:

You should have three IPs/Hostname i.e.

1. Public Hostname/IP (Physical Interface):
Public Hostname should register in DNS or /etc/hosts file and should be accessible i.e. one can ping it.

2. VIP Hostname/IP(Logical Interface):
VIP Hostname/IP should register in DNS or /etc/hosts file and should NOT be accessible i.e. one CANNOT ping it.

NOTE: in case of IPMP VIP should be LOGICAL interface.

3. Private Hostname/IP(Physical Interface):
Private Hostname should register in DNS or /etc/hosts file and should be accessible i.e. one can ping it.

cheers

group.dba does not exist, projmod error

Gabi asked me to help her in configuring Oracle 11g new RAC servers, she was getting errors on kernel parameters configuration in Solaris 10. According to my own written RAC pre installation guide on Solaris 10, i was deceived by ORACLE's official documentation they didn't mentioned about "projadd" so when she was trying to execute projmod command to set kernel parameters, she was getting error "group.dba does not exist".

after realizing that there is of course some steps messing i consult uncle google ;) and found a post , where i found the missing block i.e. projadd command, in fact we need to first add a project only then after we can projmod (modify) it. here is the command:

#projadd -U oracle -K "project.max-shm-memory=(priv,10G,deny)" group.dba

cheers