The ways to configure dhcp in 9800

[interfacedy]

Hi In catalyst 9800 wlc, there are two ways that I know to configure dhcp for wifi user. One is to configure dhcp server ip address in policy. Second is to add ip help-address in its vlan. However, I notice Guest wifi can work well, but the two ways of dhcp configuration do not exist in the WLC. My question is how dhcp work without dhcp configuration in the wlc? Maybe there is another way to work for dhcp? Thank you

[ammahend]

The 2 ways you described are both ways of configuring IP helper address, what you are doing by this configuration is changing DHCP broadcast message to unicast and sending it to specific server.

If you do not configure either IP helper on WLC, then DHCP broadcast will remain broadcast as if passes through WLC and will flood everywhere broadcast boundary of interface the SSID is mapped to and will reach your upstream switch where the WLC is connected and on that switch's Guest VLAN SVI most likely you have IP helper address configured and that's how Guest is getting an IP.

hope this helps.

[balaji.bandi]

Check there is internal and external, how it can be configured here :

https://www.cisco.com/c/en/us/td/docs/wireless/controller/9800/config-guide/b_wl_16_10_cg/dhcp-for-wlans.html