Hi,  For the question 1 you can change it through GUI --> Cluster Management --> Network configuration or through isi network modify command line.  Question 2, not sure to understand. You can add, remove, change node configuration and IP settings at any time. You can add nodes and scale your cluster from 3 nodes to 144 nodes.  Question 3, for IP internal you can choose any IP, it's internal [IMAGE] Example below : In a subnet, YES you can use for example, *.*.*.56 and *.*.*.97.  Question 4, For internal you can't use DHCP adresse because it's Infiniband switch, not plug on the network. Internal communication only. For External, you have to define a Range of IP but IP's could be like in your example.You can also use VLAN ID in a subnet.  Hope it'll help,
1. What if i have already given internal and external IP address for a node. How to change it later? When I login to a node, I am not sure what is the command to reconfigure the IP settings.  2. Is it possible if I create two separate nodes at two different time with different external and internal ip addresses. Can I add them into a single cluster later?  3. In doc, it ask me to give IP range for internal and external Ip addresses. What if the available IP addresses are not in sequence. How to give them discrete ip addresses (for example, *.*.*.56 and *.*.*.97)?  4. Can I give DHCP IPs for internal and external IP addresses? Can I make Isilon to choose the IP addresses by himself from the available vLAN?
Few questions regarding configuring Isilon at ESX