Network adapter communication between partitions and the HMC

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After a partition has been started, it uses the network adapter to communicate with the Hardware Management Console (HMC).

Both the HMC and the partition must be configured so they can use the network adapters to communicate with each other. The partition must be configured to identify the HMC (or HMCs) on the network. It is recommended that the network be configured using a Domain Name Service (DNS) server.

You can use either fully qualified host names or short host names to identify partitions and HMCs. However, it is recommended that each partition and HMC be identified using a fully qualified host name, as this identification ensures unique naming of all the partitions and the HMC in the network. Fully qualified host names cannot be more than 100 bytes in length.

The HMC and partitions can also be configured using a short host name, where the domain name is not defined. This is typically done in a private or test network. If the HMC is defined using a short host name, you must perform extra network configuration steps to ensure correct communications between the partitions and the HMC. If you use short host names rather than fully qualified host names, make sure that the short host names are unique and that the mappings to IP addresses are properly specified.

The search order between the local /etc/hosts file and the DNS can be specified using the /etc/netsvc.conf file or /etc/irs.conf file.

The following examples illustrate the scenarios supported:

If you are using DNS and your partition and the HMC are using fully qualified host names, then no additional network configuration is required.
If you are using DNS and your partition is using a short host name, such as partition_1 and the HMC is also using a short host name, such as hmc123, both must be added to the local /etc/hosts file, as shown in the following:
```
  root@partition_1
-> cat /etc/hosts

127.0.0.1 	loopback localhost	

9.3.3.151	partition_1.mydomain.mycompany.com  partition_1
9.3.3.152	hmc123.mydomain.mycompany.com  hmc123
```
Note: You must include the fully qualified host name in addition to the short name when a DNS is present.
If you are not using DNS and your partition is using a fully qualified host name, such as partition_1.mydomain.mycompany.com, and the HMC is also using a fully qualified host name, such as hmc123.mydomain.mycompany.com, both must be added to the local /etc/hosts file, as shown in the following:
```
  root@partition_1.mydomain.mycompany.com
-> cat /etc/hosts

127.0.0.1 	loopback localhost	

9.3.3.151 	partition_1.mydomain.mycompany.com
9.3.3.152	hmc123.mydomain.mycompany.com
```
If you are not using DNS and your partition is using a short host name, such as partition_1 and the HMC is also using a short host name, such as hmc123, both must be added to the local /etc/hosts file, as shown in the following:
```
  root@partition_1
-> cat /etc/hosts

127.0.0.1 	loopback localhost	

9.3.3.151	partition_1
9.3.3.152	hmc123
```
Your HMC is using a short host name, such as hmc123, and you would like to use both a fully qualified host name and a short host name for the HMC. In order for your partition to correctly communicate with the HMC, you must specify the short host name before the fully qualified host name in the partition's /etc/hosts file, as shown in the following:
```
  root@partition_1.mydomain.mycompany.com
-> cat /etc/hosts

127.0.0.1 	loopback localhost

9.3.3.151	partition_1.mydomain.mycompany.com
9.3.3.152	hmc123 hmc123.mydomain.mycompany.com
```