Identifying primary DHCP service for Guest network

Hello experts,

I am at a site and they use cisco WLC 5500 wireless controller and they have defined all the SSIDs , one of the SSID is the guest and I am checking the interface defined and it is clearly showing that it is on VLAN 50 the IP of the interface is given, plus the gateway which is same as the primary DHCP 10.20.10.1.

I checked the core switch and there is VLAN 50 but just the vlan is defined but there is no SVI for vlan 50 and there are no DHCP services on the core, I checked the Microsoft servers and I do not see the scope for vlan 50. I am wondering how the clients are getting a dhcp IP when they access the guest SSID. I can not find this gateway or primary DHCP 10.20.10.1

This client also uses cisco ISE, I have access to the cisco ISE but it uses different IP and I do have access to it but I am not getting clarity on this network, Any suggestions on how to find this dhcp server or service will be great help.
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SR ZakNetwork Solutions Asked:
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JustInCaseCommented:
Recommended designed for guest VLAN is to terminate it on DMZ firewall, check there.
Other solution - check ARP of default gateway on host and trace default gateway MAC address through switch ports to find out where it is located.
Iamthecreator OMIT Admin/EE Solution GuideCommented:
Is it not the management IP address of the Cisco controller?
Benjamin Van DitmarsSr Network EngineerCommented:
sounds like an interface on the firewall where this interface lives.

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Andy BartkiewiczNetwork AnalystCommented:
The controller itself could be setup as a DHCP server
SR ZakNetwork Solutions Author Commented:
the guest dhcp scope is defined in the firewall. I figured it out , many thanks.
JustInCaseCommented:
You're welcome.
Benjamin Van DitmarsSr Network EngineerCommented:
Always Welcome on EE
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