WLC Catalyst 9800L HA question

[jjtech]

Hi,

I am replacing an old WLC with 2 new Cisco Catalyst 9800L Wireless Lan Controllers with HA.

I have 2 questions please that I need your experts input on:

• Before doing the HA redundancy configuration (RP+RMI), what configuration specific to the standby WLC should I do on it only? Hostname, Management IP, SSH access, needed VLANs? Will everything else be taken from from the Active WLC?
• What should be done from the access points perspective to make sure they will actually use the backup WLC in case of failure? I will be using option 43 on the DHCP server to make sure the APs know where to register. Should I specify only the wireless management interface IP address of the Active WLC in option 43 ? Will this IP be assumed by the backup WLC in case of failure?

I know these may be basic questions, however I am new to the High Availability setup with Cisco WLC, and I couldn't find the needed details in the Cisco documentation.

Thanks,

[MHM Cisco World · Accepted solution]

• Before doing the HA redundancy configuration (RP+RMI), what configuration specific to the standby WLC should I do on it only? Hostname, Management IP, SSH access, needed VLANs? Will everything else be taken from from the Active WLC? Yes correct' only these config need other config is done in active later and bulk sync to standy 
• What should be done from the access points perspective to make sure they will actually use the backup WLC in case of failure? I will be using option 43 on the DHCP server to make sure the APs know where to register. Should I specify only the wireless management interface IP address of the Active WLC in option 43 ? Will this IP be assumed by the backup WLC in case of failure? No need anything from AP' the AP see only one wlc IP and use it' when active failed this IP is move from active (old) to standby (new active).

MHM

[jjtech]

Thank you for the reply.

So for option 43 I use the IP address of the wireless management interface on the Active WLC ? I mean there are no dedicated separate virtual IP (similarly to the virtual IP used in the HSRP concept for example) ?

[MHM Cisco World]

No op43 will be only IP of active wlc.

wlc HA dont like hsrp which use VIP of hsrp group as GW in dhcp.

MHM

[Rich R]

It operates like a switch stack or cluster - so the HA-SSO pair only has the one single name and IP address which you use.

[ammahend]

Correct.

[balaji.bandi]

Most of the configuration required on Main WLC only, Standby need only basic config, so most configuration sync from Primary

have you checked below :

https://www.cisco.com/c/en/us/support/docs/wireless/catalyst-9800-series-wireless-controllers/213915-configure-catalyst-9800-wireless-control.html

[jjtech]

Thank you Balaji, the article is helpful, but they didn't give much details about the access point side of the configuration.

[balaji.bandi]

You mean access point onboarding : Cisco have each section that is for HA setup.,

there are many documents available - how you can join the AP to WLC and deploy other parameters :

example guide below :

https://www.cisco.com/c/dam/en/us/td/docs/wireless/controller/9800/17-4/deployment-guide/c9800-webui-dg.pdf

good blog :

https://mrncciew.com/category/ap-registration/

[Rich R]

From the access point point-of-view it looks like a single WLC.

[marce1000]

 - FYI : https://www.cisco.com/c/en/us/support/docs/wireless/catalyst-9800-series-wireless-controllers/213915-configure-catalyst-9800-wireless-control.html
     For further consistency checks after intended configuration is finished use CLI command show tech wireless (on the primary) and feed the output into : Wireless Config Analyzer

 M.

[marce1000]

 >....What should be done from the access points perspective to make sure they will actually use the backup WLC in case of failure?
                            Nothing , once the HA is operational , all of that is automatic 

 - FYI : https://www.cisco.com/c/en/us/support/docs/wireless/catalyst-9800-series-wireless-controllers/213915-configure-catalyst-9800-wireless-control.html
     For further consistency checks after intended configuration is finished use CLI command show tech wireless (on the primary) and feed the output into : Wireless Config Analyzer

 M.