HP XC System Software Administration Guide Version 3.0

7. Network Administration
This chapter addresses the following network topics:
• Network Address Translation Administration (page 77)
• Network Time Protocol Service (page 78)
Network Address Translation Administration
Network Address Translation (NAT) is administered on the head node only when one or two nodes are
configured with the external role as NAT servers. When three or more nodes (other than the head node)
are configured as NAT servers, these nodes relieve the head node of NAT duty. You establish the external
role assignment when you configure the HP XC system using the cluster_config utility.
When nodes are configured as NAT clients, the default gateways are established. Each NAT client has two
gateways: a primary gateway and a secondary gateway.
Figure 7-1. illustrates a system with two NAT servers (n4 and n8) and six NAT client nodes (n[1-3,5-7]).
The primary and secondary gateways for each NAT client are shown.
Figure 7-1. NAT Administration Example NAT Administration Example
Figure 7-1. shows how the gateway assignments alternate between NAT servers n4 and n8 to ensure a
distributed load on the NAT servers.
These alternate assignments are useful if either of the NAT servers fails. All the NAT clients can access the
remaining NAT server through the working default gateway route.
When the failed NAT server returns to service, some NAT clients will resume using it.
To improve the distribution of NAT server usage between the NAT clients, issue the service
default_gateway reset command on each NAT client node. For the system shown in Figure 7-1., the
following command line issues this service command to all the NAT clients:
# pdsh -a -x n[9,4,8] service default_gateway reset
Network Address Translation Administration 77