Identifying issues
There is a problem with name resolution if any of these tests fail. ESX/ESXi hosts 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 that you delete the file
/etc/FT_HOSTS (or
/etc/opt/vmware/aam/FT_HOSTS and
/var/run/vmware/aam/FT_HOSTS ) on all affected ESX/ESXi hosts.
- Verify that all ESX/ESXi hosts can ping each other by short name. All ESX/ESXi hosts 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).
- Verify that all ESX/ESXi hosts can nslookup each other.
Use nslookup (reverse IP address lookup) to verify that the appropriate name is 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
- Verify that all ESX/ESXi hosts can reverse nslookup each other.
Use nslookup (forward IP address lookup) to verify that the appropriate IP address is 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
- Verify that the DNS server has both an A Record (Address Record) and a C NAME record (Canonical name record) configured for each ESX/ESXi hosts.
Additional checks for VMware High Availability (HA) environments - ESX/ESXi 3.x and 4.x Only
Perform these additional checks for VMware High Availability environments with ESX/ESXi versions 3.x and 4.x (this does not apply to ESXi 5.0):
- Verify that the reported host name is in lowercase when you run:
[root@esx-server-1 /]# hostname
[root@esx-server-1 /]# hostname -s
- Verify that all host names in /etc/hosts are in lowercase.
- Verify that the search domain in /etc/resolv.conf is in lowercase.
- Verify that the host name in /etc/sysconfig/network is a fully qualified domain name, and is lowercase.
- Verify that the host name in /etc/vmware/esx.conf is a fully qualified domain name, and is lowercase.
- If your ESX/ESXi hosts are registered in DNS, verify that your system host name is lowercase and the record is a A name. Run this command to ensure the FQDN is resolvable and all lowercase:
nslookup short_hostname
- Verify that all primary Service Consoles in the VMware HA cluster have the same name.
- Verify that all primary Service Consoles are in the same IP subnet.
Note: If a VMotion VMkernel port is on the same vSwitch as the primary Service Console, or if a host has multiple Service Consoles, see
Incompatible HA Networks appearing when attempting to configure HA (High Availability) (1006541).
Configuring hosts files on ESX/ESXi
The hosts file on the ESX host is located at
/etc/hosts .
Open the file for editing using a text editor such as
nano or
vi .
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
Notes:
- 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/ESXi hosts in the cluster.
- There must be an entry for every ESX/ESXi host 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.
Note: This issue has been resolved in vCenter 2.5 U3 and above. For more information, see VMware HA Can Be Configured on a Cluster Regardless of the Letter Case of the ESX Server Host Names in the Resolved Issues section of the VirtualCenter 2.5 Update 3 Release Notes.