Configuration of dhcp at c9800 wlc

[Leftz]

Hi We can setup dhcp at Policy ----> Advance --->DHCP,  and Configuration ---> vlan SVI to setup ip help address 

What is difference between the two ways? Thanks

[marce1000]

  - Checkout : https://www.cisco.com/c/en/us/products/collateral/wireless/catalyst-9800-series-wireless-controllers/guide-c07-743627.html#DHCPbridgingandDHCPrelay , in any case when configuring the controller it is always advisable to have a configuration healt check with https://cway.cisco.com/wireless-config-analyzer  , that tool needs the output of CLI :  
                                                                                                               show tech wireless , 

 M.

[Leftz]

Thanks for your reply! The second link cannot be opened in our location. The first document talks about configuration on SVI. but it does not talk about configuring dhcp via policy like the below

[marce1000]

  - You may try https://cway.cisco.com/wireless-config-analyzer with other browser (too) , to check that it really is not accessible , because it is a rather useful tool , 

 M.

[Scott Fella]

Don't get too carried away with options.  If you by default use ip helpers on the avi, continue to do that.  Options on the controller like the 9800 is the same as AireOS and it will proxy that request to a DHCP server.  Maybe if you are testing and want to point DHCP to a different server, you can use the option on the controller to do that testing.  Other than that, the preference is to not use that on the controller and define the ip helper on the svi.

If you still have questions, just test it out.  Create a new test said mapped to a new profile and look at the behavior.  Maybe you will prefer to do it one way vs the other.

[Rasika Nayanajith]

Best practice is not to configure DHCP relay on 9800 (configure it on upstream device).

AireOS WLC provide DHCP proxy and 9800 is not. Simply use 9800 L2 device and only have single SVI for wireless management

HTH
Rasika
*** Pls rate all useful responses *** 

[Leftz]

@Rasika Nayanajith 

"Best practice is not to configure DHCP relay on 9800 (configure it on upstream device). "

we can configure ip help address in SVI. do you mean we mean we do not need to configure ip help address in SVI or something else? 

[Scott Fella]

"configure it on upstream device"  Means you configure your ip helper and any other DHCP setting on the SVI.

[Rasika Nayanajith]

For wireless client vlans, you should not define SVI on 9800 WLC. It should only have L2 vlan.

SVI should be on upstream switch/firewall and your helper address should be configured on that upstream device, not on 9800

Hope that makes sense

Rasika
*** Pls rate all useful responses ***

[Leftz]

@Rasika Nayanajith Now i know your meaning. There are two SVI in this system. in upstream switch and in 9800 wlc. you mean setup ip help address in upstream switch for client vlans

How about this way to configure dhcp? Configuration --- Tags & Profile --- Policy --- Advance --- DHCP ---DHCP server ip address

[Rasika Nayanajith · Accepted solution]

Ideally there should not have two SVIs defined (one in 9800 & one in upstream). Recommended approach is only have SVI on your upstream switch and no SVI at all on your 9800.

That eliminate need of IP helper address on 9800 completely.

HTH
Rasika
*** pls rate all useful responses ***

[Leftz]

Thanks Rasika