Hosts file configuration for successful CA Performance Management Suite installation
Article ID: 32020
Updated On:
Products
Issue/Introduction
Description:
When installing the IM Suite, if the hosts file is not configured properly to accommodate for possible DNS problems it will cause functional issues with the product.
Environment
Release: IMDAGG99000-2.5-Infrastructure Management-Data Aggregator
Component:
Resolution
The IM suite requires that the hosts files on the various servers involved, the Data Repository, the Data Aggregator, the Data Collector and the CA Performance Center (CAPC) servers, be configured properly for correct functionality.
The hosts file involved is found in the /etc directory of Linux systems the IM suite is installed on.
A default file would look like this:
[root@HOSTNAME etc]# more hosts
# Do not remove the following line, or various programs
# that require network functionality will fail.
127.0.0.1 localhost.localdomain localhost
::1 localhost6.localdomain6 localhost6
Regardless of the successful function of DNS in the network, a properly configured hosts file contains both the short Host Name and FQDN Host Name of a server, not just the short Host Name. That might work while DNS is properly functioning. But it raises the risk that the IM suite will go down if DNS has problems since the servers will no longer be able to successfully communicate with each other due to possibly failing DNS resolution queries.
To alleviate this, to ensure that even in the presence of DNS network problems in the environment, that the IM product suite of servers continue to communicate and function correctly, the hosts file should appear as follows in this example.
Lets assume we have four servers with the following Host Names:
Data Repository = DRHost.ca.com = IP 10.10.10.2
Data Aggregator = DAHost.ca.com = IP 10.10.10.3
Data Collector = DCHost.ca.com = IP 10.10.10.4
CAPC = CAPCHost.ca.com = IP 10.10.10.5
While not all systems will talk to each other, like the DC doesn't talk directly to the DR, it is often easiest to add the same entries to all four hosts files on the four systems to ensure successful communications between the systems. In this scenario, each servers hosts file should at a minimum look like:
[root@HOSTNAME etc]# more hosts
# Do not remove the following line, or various programs
# that require network functionality will fail.
127.0.0.1 localhost.localdomain localhost
::1 localhost6.localdomain6 localhost6#
#
10.10.10.2 DRHost.ca.com DRHost
10.10.10.3 DAHost.ca.com DAHost
10.10.10.4 DCHost.ca.com DCHost
10.10.10.5 CAPCHost.ca.com CAPCHost
Please also note that a common mistake is to configure the hosts file as follows, using MY-Host.ca.com as the host name, and 1.2.3.4 as the IP address in the following examples.
[root@HOSTNAME etc]# more hosts
# Do not remove the following line, or various programs
# that require network functionality will fail.
127.0.0.1 MY-Host.ca.com MY-Host localhost.localdomain localhost
::1 localhost6.localdomain6 localhost6
The problem here has to do with the association to the loopback IP address in the first line to the host name. While the host would be accessable, it would return the loopback as the IP for the host instead of the real IP. It would also not be successful in being queried via DNS with its host name as that is not present in the hosts file associated to the IP address which it should be.
Another common error in setting up the hosts file is seen in the following example.
[root@HOSTNAME etc]# more hosts
# Do not remove the following line, or various programs
# that require network functionality will fail.
127.0.0.1 MY-Host.ca.com MY-Host localhost.localdomain localhost
::1 localhost6.localdomain6 localhost6
10.2.3.4 MY-Host.ca.com MY-Host
In this case while the host would be successfully queried via DNS, in the CAPC UI reference to the host would end up showing an IP of 127.0.0.1 instead of the real IP.
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