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Identifying issues with and setting up name resolution on ESX Server

Symptoms

  • Unable to configure VMware High Availability (HA)
  • Configuring VMware HA fails at about 97% completion
  • Reconfiguring VMware HA fails
  • Adding an ESX host to a cluster fails
  • Enabling VMware HA in a cluster fails
  • The following errors are generated when attempting to configure VMware HA:
    • An error occurred during configuration of the HA agent on the host
    • HA agent on <ESX> in cluster <cluster> in <Datacenter> has an error
    • cmd addnode failed for primary node:/opt/vmware/aam/bin/ft_startup failed

  • Host fails to remediate or exit Maintenance Mode. The following errors appear:

    Operation timed out

    In VirtualCenter (Tasks view) you see the messages:

    There are errors during the remediation operation
    Failed to find host

Purpose

The errors listed in the Symptoms section are generated as a result of name resolution issues.
 
This article guides you through identifying issues with name resolution which can seriously impact the normal operation of ESX, particularly in HA clustered environments. The article also details correctly configuring host files when there is no DNS server in the environment or if the DNS server is incorrectly configured.

Resolution

Identifying issues

There is a problem with name resolution if any of the following tests fail. ESX Servers must be able to find each other by: 
  • IP address
  • Short Name
  • Fully Qualified Domain Name (FQDN)
If an issue with name resolution has been identified it must be resolved either on the DNS server or by using hosts files.
 
Note: After making any changes to DNS or hosts files ensure you delete the file /etc/FT_HOSTS (or /etc/opt/vmware/aam/FT_HOSTS ) on all ESX Servers affected.
 
  1. Verify that all ESX Servers can ping each other by short name. All ESX Servers in the environment must be able to ping each other by using short name only. For more information, see Testing network connectivity with the Ping command (1003486) .

  2. Verify that all ESX Servers can nslookup each other.

    Use nslookup to verify that the right name is being associated to a particular IP address.

    For example:

    [root@esx-server-1 /]# nslookup 192.168.0.5
    Server:  192.168.0.7
    Address: 192.168.0.7#53

    5.0.168.192.in-addr.arpa name = esx-server-2.domain.com.

  3. Verify that all ESX Servers can reverse nslookup each other.

    Use nslookup to verify that the right IP address is being associated to a particular name.

    For example:

    [root@esx-server-1 /]# nslookup esx-server-2
    Server:  192.168.0.7
    Address: 192.168.0.7#53

    Name: esx-server-2.domain.com
    Address: 192.168.0.5

Additional checks for VMware High Availability (HA) environments

 The following are additional checks for VMware High Availability environments:

  1. Verify that the reported host name is in lowercase when you run:

    [root@esx-server-1 /]# hostname
    [root@esx-server-1 /]# hostname –s

  2. Verify that all host names in /etc/hosts  are in lowercase.
  3. Verify that search domain in /etc/resolv.conf is in lowercase.
  4. Verify that the host name in /etc/sysconfig/network is a fully qualified domain name, and is lowercase.
  5. Verify that the host name in /etc/vmware/esx.conf is a fully qualified domain name, and is lowercase.
  6. If your ESX hosts are registered in DNS, verify that your system host name is lowercase. Run the following command to ensure the FQDN is resolvable and all lowercase:

    nslookup <short hostname>

  7. Verify that all primary Service Consoles in the VMware HA cluster have the same name.
  8. Verify that all primary Service Consoles are in the same IP subnet.

Note: If a VMotion VMkernel port is on same vSwitch as the primary Service Console, or if a host has multiple Service Consoles, refer to After installation or upgrade to VirtualCenter 2.5.0 Update 2 an Incompatible HA Networks error is generated (1006541) .

Configuring hosts files on ESX Server

The hosts file on the ESX Server host is located at /etc/hosts
 
Open the file for editing using a text editor such as nano or vi .
 
Below is an example hosts file.
 
# Do not remove the following line, or various programs
# that require network functionality will fail.
127.0.0.1                localhost.localdomain         localhost
 
# Any line beginning with a pound sign is a comment and will not be read.
192.168.0.5              esx-server-1.domain.com       esx-server-1
192.168.0.6              esx-server-2.domain.com       esx-server-2
 
# The VMware Virtual Center Server must also have an entry here
192.168.0.20             virtualcenter.domain.com      virtualcenter

Note: localhost must always be present in the hosts file. Do not modify or remove the entry for localhost.
  • The hosts file must be identical on all ESX Servers in the cluster.
  • There must be an entry for every ESX Server in the cluster.
  • Every host must have an IP address, Fully Qualified Domain Name (FQDN), and short name.
  • The hosts file is case sensitive. Be sure to use lowercase throughout the environment.

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Actions
  • KB Article: 1003735
  • Updated: Mar 13, 2009
  • Products:
    VMware ESX
  • Product Versions:
    VMware ESX 3.0.x
    VMware ESX 3.5.x