Wireless Access

when provisioning an AP I always wonder about this section:

Master Discovery

( ) Use AP Discovery Protocol  

( ) Host Controller IP Address [     ]   Master Controller IP Address/DNS name [     ]

( ) Host Controller Name       [     ]   Master Controller IP Address/DNS name [     ]

it defaults to Host Controller Name with only aruba-master filled in I believe.

what exactly is the effect of these fields here? is Host equal to Local? is there any reason not to just keep using ADP? why would you enter the name or IP?

aruba-master is the default, and it puts aruba-master in front of any domain suffix it gets through dhcp and tries to resolve it, and find the controller.  The host controller name will put the DNS name, without the suffix of the master controller, if you wanted.

If you want to set a fixed ip address you would only go to the second Master Controller ip address/DNS name on the right and put in the ip address.

totally clear.

but what is the use of the host controller fields? is it just another name for local controller or is it something more?

The host controller sets the "serverip" variable in the flash of an AP.  On an AP, you can automatically allow it to discover a controller via DNS, DHCP Option or ADP (broadcast/multicast).  If you set it statically, you can set the "master" variable, or the "serverip" variable or even both to find the controller.  The "host controller" portion of the GUI sets the "serverip" variable.  If both are "master" and "serverip" are set:

"On the AP, the other end of the GRE tunnel is specified by the IP address configured variable values (in descending order of priority) <master>, <servername>, and <serverip>. If these variable are left to default values, the AP uses DNS to look up aruba-master to discover the IP address of the controller. "

Why are both of these variables available?  Way back in the day, it was required to point an AP at a local switch to terminate his GRE or IPSEC tunnel and upgrade its firmware (serverip variable), but still let the AP know who his master controller is to send statistics to.  You no longer have to set both variables manually, so just setting the master variable is all that is needed.  The paragraph above describes what is done if both variables are still set from back in the past.

thank you cjoseph for this clear explanation.

Hi,

Sorry to resurrect an old thread but I just want some clarifiation on these settings.

So we have under the master discovery settings the option to either use AP Discovery or:

Master switch IP / DNS name & TFTP server

OR

Host Switch Name & Master switch ip /dns name

What is the best practive when completing this and what are the benefits of one over the other?

Thanks

Above are the defaults, which basically will leverage any automatic discovery method available (recommended).  Besides "Use AP Discovery Protocol", every other option changes the discovery method to use a specific host or ip address to discover the master controller or to upgrade the AP code via tftp.

For example, if I wanted to use aruba2-master.domain.com instead of aruba-master.domain.com to discover the master controller, I would change the host controller name to "aruba2-master".  That would append any domain provided dhcp to aruba2-master to locate the master controller.

The master controller/ip address/dns name parameter takes an fqdn so I could accomplish the same thing by putting "aruba2-master.domain.com" or an ip address into that parameter to accomplish the same thing.

Long story short, those parameters are rarely changed from the defaults, because it would require provisioning APs or groups of the same model APs individually to accomplish this.  It is much easier to just do a DHCP option to influence behavior despite what the DNS server returns.

Thanks for the reply but I do not quite follow.

In terms of configuring this for failover, what is the prefferred option. 

Is it better to use DNS or just specify the IP of the controller?  

Is it also better to use the IP or DNS of the Virtual IP rather than the primary controller?

These parameters should not be changed.  The failover parameters are configured within the HA profile and/or the LMS/Backup LMS-ip profile on the controller.  The parameters above are used when the AP is cold-started and should not be changed.

I know but the issue we have is that some of the APs have been configured using the master Ip & tftp settings, some have been configured using the host name & master IP setting and some are using AP discovery.

I would like to standardise this for the APs if possible.

Change them back to the defaults in the screenshot and they should all rely on your default discovery method (DNS or DHCP option).

If this is a large-scale change, I would consult your local Aruba SE, an Aruba reseller or Aruba TAC before you make that change.  There is little reason to change those parameters from the defaults except in limited circumstances.

This is the query I have what should the "default" discovery method be (DNS or DHCP?) and how do I change between both which method I want to use?

My post here:  http://community.arubanetworks.com/t5/Wireless-Access/master-discovery-automatic-host-or-master-controller/m-p/375268/highlight/true#M77808 has the screenshot of how it should be by default.  It should not be changed from that.  If you simply configure "aruba-master" in your DNS server to point to the ip address of your master controller or the VRRP between your master and backup master, you should be done...  The APs will come up, resolve aruba-master.yourdomain.com and get the correct configuration for their AP-Group, including HA and/or LMS-IP settings.  Those HA and LMS-ip settings will then determine where the APs go from there.  Again, the settings in the screenshot are what the APs will look for when they are cold booted and the majority of users use the DNS method, because it is easy to do for the enterprise.