Change of DNS Server for ESX Hosts ?

[TonyJK]

Our network administrator is going to change the IP Address of DNS Server. In this way, we are going to change the corresponding ones in ESX Hosts.

We would like to know

1) Can we change the DNS Server on running ESX hosts without entering maintenance mode ?

2) In what circumstances the ESX Hosts will make use of the DNS Servers ?

3) From memory, we should add all ESX hosts IP addresses in the hosts file in Service Console, where is that hosts file located at ?

Thanks

[athlon_crazy]

1) Can but new setting will only take effect after you reboot the system

2) Example when you mount any ip storage via fqdn instead ip address & etc

3) Not necessary when you have valid & workable DNS server but it's good as a backup or second option when your DNS server down.

vcbMC-1.0.6 Beta

vcbMC-1.0.7 Lite

[kopper27]

I can add name resolution (DNS) is pretty important when you have HA configured...

[bulletprooffool]

Tony, you can add more DNS servers, without removing the old ones.

Restart the management network on the host will reset the resolution - you do not require a reboot.

I'd suggest adding the new DNS on each host before the admin makes the change, then once the change has been made, remove tyhe old entries.

It is worth finding out if your adnmin can have both IPs allocated to the DNS server for a short while to make the transisiotn neater and easier and less risky.

[TonyJK]

Does "Restart the management network" mean running the "service mgmt-vmware restart" command at the Service Console ?

Thanks again

[Jain · Accepted solution]

Tony,

use "service network restart " command to restart network service

Also remember that -

HA highly dependant on DNS, HA wont work without proper DNS configuration. ESX servers and vCenter server should be able to resolve name(FQDN)/IPs in both direction to get HA work.

[TomHowarth]

HA highly dependant on DNS, HA wont work without proper DNS configuration. ESX servers and vCenter server should be able to resolve name(FQDN)/IPs in both direction to get HA work

Your statement is not entirely true, HA is highly dependent on standardised naming, there is no requirement for DNS, DNS just makes it eaiser to setup as there is a single location. Correctly configured Host files work just as well. I have worked in locations where there is no DNS, and host file configuration works fine

If you found this or any other answer useful please consider the use of the Helpful or correct buttons to award points

Tom Howarth VCP / vExpert

VMware Communities User Moderator

Blog: www.planetvm.net

Contributing author on "[VMware vSphere and Virtual Infrastructure Security: Securing ESX and the Virtual Environment|http://www.amazon.co.uk/VMware-VSphere-Virtual-Infrastructure-Security/dp/0137158009/ref=sr_1_1?ie=UTF8&s=books&qid=1256146240&sr=1-1]”. Currently available on roughcuts

[TonyJK]

Dear Tom,

Many thanks for your advice.

Unfortunately, I have already used up my "Helpful" and "Correct" buttons.

Thanks again,

Tony

[Jain]

Thanks Tom for the comments,

if we setup host-file with Hostnames of all ESXs & vSphere server is that enough to function HA ? no FQDN required ?

[TomHowarth]

Yes it is, I have used it many times, also remember that vCenter needs to be in the host files on each Host server too

If you found this or any other answer useful please consider the use of the Helpful or correct buttons to award points

Tom Howarth VCP / vExpert

VMware Communities User Moderator

Blog: www.planetvm.net

Contributing author on "[VMware vSphere and Virtual Infrastructure Security: Securing ESX and the Virtual Environment|http://www.amazon.co.uk/VMware-VSphere-Virtual-Infrastructure-Security/dp/0137158009/ref=sr_1_1?ie=UTF8&s=books&qid=1256146240&sr=1-1]”. Currently available on roughcuts

[msuvanto]

Now what would be even more interesting for me is to know how to change it for 60 hosts via a script?

[Troy_Clavell]

have a look at this thread

http://communities.vmware.com/thread/213132