Anchor Guest controller and DHCP configuration

[alex.roth]

I checked the cisco documentation about the DHCP configuration but I´m not 100%sure which DHCP server address I must use.

I  used as example the scope 10.240.97.0/24 for our Guest Users. In this range are the DHCP scope and the Guest interface configured. For the management I used as example the range 10.240.96.0/24.Now I configured our Guest WLC and I insert on the Guest interface as Primary DHCP address the Guest interface address. After I applied I got the message I can´t use this DHCP address. Now I checked the cisco and found following description:

“If DHCP services are to be implemented locally on the anchor controller, populate the primary DHCP server field with the management IP address of the controller"

Means it now I must insert as the IP for the Primary DHCP Server on the Guest interface  the IP from the management

Interface and the controller will then forward the traffic to the internal DHCP scope on the Guest subnet and wil sent it back ?
( DHCP proxy is on the Guest WLC  enabled ) .

Thanks

Al

[Mats Nilson · Accepted solution]

You must use the WLC's management IP as the DHCP server if you want to use the internal DHCP server.

[Saravanan Lakshmanan · Accepted solution]

For Anchor you can use either internal or external dhcp server.

Means it now I must insert as the IP for the Primary DHCP Server on the Guest interface  the IP from the management

Interface and the controller will then forward the traffic to the internal DHCP scope on the Guest subnet and wil sent it back ?

Yes. WLC forwards the unicast dhcp req to management ip for guest interface. All cpu generated traffic by default uses management interface as source address i.e., snmp, radius, ping...

Is your question whether you need routing between guest and management interface.

No, routing is not required in this case bcoz the interface residing on WLC's management. Also for proxy it uses the virtual ip address for dhcp instead of actual dhcp ip. And only wireless client can get ip from WLC's internal dhcp server.

If you're using dhcp proxy on wlc and having external dhcp server on different vlan then yes you need routing between the two vlans.