WLC CAPWAP join with DNS name resolution option

[vinod rathore]

Hello Everyone,

I'm running 2504 and 1700 series of APs across locations. If i would like to use DNS name resolution "Cisco-capwap-controller.domainname" method. the challange is - each location is having saperate 2504 and if i put dns record for "cisco-capwap-controller" at each location with its respective controller IP, its gonna meshup as all the DNS across locations are syncing its database.

i.e.

Site A WLC - 10.10.1.1

Site B WLC - 10.20.1.1

Site B WLC - 10.30.1.1 

then how to set it up ?

Thanks in advance !!

[Sandeep Choudhary · Accepted solution]

if you have this problem then why dont u use any other method.

lIke:

1. dhcp option 43

2. AP and WLC in same subnet(layer 3 - broadacst)

3. with IP helper function

more info: http://www.cisco.com/c/en/us/support/docs/wireless-mobility/wireless-lan-wlan/70333-lap-registration.html

Regards

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[vinod rathore]

Hello Sandeep, 

You're correct, currently i'm using IP helper-address function.

Just curious to know if i wish to go for DNS option could it be implemented in my scenario.

Thanks for input..

[Sandeep Choudhary]

Hi Vindo,

Normally you can bundle multiple WLC IP to a single DNS name. in other words You can add multiple entries for the same host name in the DNS.

You create four entries for same name for all your controllers. If one is not reachable by the AP then the other one will be tried.

From this link:http://www.cisco.com/c/en/us/support/docs/wireless/4400-series-wireless-lan-controllers/107606-dns-wlc-config.html

"When an AP receives an IP address and DNS information from a DHCP server, it contacts the DNS to resolve CISCO-LWAPP-CONTROLLER.localdomain. When the DNS sends a list of controller IP addresses, the AP sends discovery requests to the controllers."

My recommnadation is to use DHCP option 43 or ip helper command to join AP to wlc.

Regards

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[vinod rathore]

Sandeep,

Yes, i had created multiple entry for "CISCO-LWAPP-CONTROLLER.localdomain" 

on site A DNS -  10.10.1.1-CISCO-LWAPP-CONTROLLER.localdomain

on site B DNS -  10.20.1.1-CISCO-LWAPP-CONTROLLER.localdomain

on site C DNS -  10.30.1.1-CISCO-LWAPP-CONTROLLER.localdomain

As i mentioned above all DNS replicate its database to each other and keep its identical across domain.

now each DNS has 3 entry for "CISCO-LWAPP-CONTROLLER.localdomain"

in this case DNS may respond with remote site WLC IP though local site WLC is UP.

(Site A DNS may respond with 10.10.1.1 or 10.20.1.1 or 10.30.1.1) 

[vinod rathore]

In this case my Site A access-point may join Site B or Site C WLC though it shoudn't be until local WLC is down.

[Sandeep Choudhary]

Yes that correct.

What you can do is, manually conifgure each AP with there resptcive location WLC IP and name as primary. Otherwise as u said APs from Site B will joing to site A.

Regards

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[Scott Fella]

Like Sandeep mentioned, you need to provide the high availability information for the primary, secondary and or tertiary on each AP. This will tell the AP the WLC it needs use for each priority. 

DNS and all the other methods is just to perform the initial join and might be easier for you to just use one WLC for that piece so that you know if a new AP comes online that the AP should always come up on that controller. The issue again will be when the AP has downloaded the image and reboots, that's when the AP already knows that WLC and all the others in the same mobility group. Then the AP will come up on one of the three WLC's.  Since all three sites are in different locations, each WLC should have a different mobility and RF group name. Now you don't have to go around and change this now, just wanted to explain why you would have it different especially with new AP's that join.

-Scott

[vinod rathore]

Yeah, for intial join process i'm using ip helper-address and its eficiently working well in my case. Once my AP get joins to WLC i'm pushing primary, secondary and teriary WLC's config to APs.

While exploring DNS option in my case i found dfficult to implement.

It seems it would completly depends on which IP DNS serves to AP CAPWAP join request. 

As we can't change hardcoded "cisco-capwap-controller.localdomain"

[Sandeep Choudhary]

Exactly..... this is the only correct procedure.

My recommandation is to use DHCp option 43 for each site.

Regards

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