HP XC System Software Administration Guide Version 4.0

Improved Availability Is Not in Effect
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. By default,
each NAT client has a single gateway. If a NAT server fails, however, the NAT client loses
connectivity.
You can configure a system for multiple gateways to lessen the possibility of loss of connectivity,
but the system may have performance problems. External access from NAT clients using UDP
has been shown to work well, however. Use the following procedure to create a NAT client
configuration with multiple default gateways.
1. Ensure that all available software patches for this release have been applied to the system.
2. Use the dbsysparams command to modify the value of NAT_GATEWAYS from single to
multiple:
# /opt/hptc/sbin/dbsysparams "NAT_GATEWAYS"
NAT_GATEWAYS: single
# /opt/hptc/sbin/dbsysparams -s "NAT_GATEWAYS" "multiple"
3. Use the dbsysparams command to verify the results:
# /opt/hptc/sbin/dbsysparams "NAT_GATEWAYS"
NAT_GATEWAYS: multiple
4. Rerun the nconfig and cconfig commands to create the /etc/init.d/
default_gateway file on each node so that the file contains multiple default gateway
definitions:
# pdsh -a "service nconfig nconfigure"
# pdsh -a "service nconfig nrestart"
When multiple NAT gateways are used, the NAT configuration code creates logical pairs of NAT
servers from the usable NAT servers for the client as a way to coordinate clients and servers.
During NAT client configuration, the /etc/init.d/default_gateway script is created on
each NAT client. This script contains the calls to add the default gateways for the client; this is
how the NAT client identifies which NAT server is assigned to it.
The following kernel values in the /etc/init.d/default_gateway script control how
frequently the route table is rewritten and reevaluated:
sysctl net/ipv4/route/gc_timeout=10 > /dev/null
sysctl net/ipv4/route/secret_interval=10 > /dev/null
Clients reevaluate their routes on a regular basis, balancing the usage between the NAT servers;
thus, a particular client could be using either of the two NAT servers at any particular time. Use
the traceroute command to determine which of the NAT servers configured in the /etc/
init.d/default_gateway script serves a given client at a given time.
9.2 Network Time Protocol Service
By default, the head node acts as the primary Network Time Protocol (NTP) internal server for
all other nodes in an HP XC system. Other nodes are NTP clients of the head node.
You can specify where the NTP server obtains its time reference during the initial configuration
of the HP XC system; up to three external time servers are accepted if the internal server is
connected to an external network. You can also specify the internal server's clock as the time
reference instead.
If you encounter a clock synchronization problem, examine the /etc/ntp.conf file on the
internal server and the /etc/ntp.conf file on the node that is experiencing the problem.
You can restart the NTP service (ntpd) with the following command:
# service ntpd restart
132 Network Administration