9800s with DHCP Relay

[mumbles202]

So currently I have a pair of 9800-Ls deployed in HA with a few APs attached.  I have the management interface tagged on vlan 10, which is the only SVI configured.  I have 2 additional vlans defined and I'm able to get dhcp when I have a dhcp server available within the vlan that can answer dhcp requests.  Unfortunately I need to remove the dhcp server from 1 of the vlans so will need to create an additional scope on a Windows dhcp server.  To accomplish this, do I just need to create an SVI for 1 of the 2 L2 vlans previously defined and then add a dhcp server as I would on a 2504 or 3504?  

[Scott Fella]

You can, but why not just use ip helpers on the svi?  That is the most ideal configuration for DHCP.

[balaji.bandi]

why not configure on the VLAN SVI ip helper address ?

interface Vlanxxx
ip address x.x.x.x  255.255.255.0
ip helper-address y.y.y.y

[mumbles202]

I agree ip helpers make the most sense so I will give that a try.  I guess I'm still a little new to the 9800s and haven't found the balance of what should be done in the GUI vs the CLI.  But I'll add an SVI for 1 of the 2 vlans and then point it to the correct server internally and give that a go.  Thanks.

[Scott Fella]

You just have to get use to both the GUI and the CLI.... it's just time that you need.  My thing is be smart with what you do, just because it's there, doesn't mean you should use it.  DHCP proxy has its issues depending on what is serving your DHCP addresses.  I don't have multiple SVI's on the controller, just one that is used from management and wireless management.  

[mumbles202]

Thanks.  At the moment I have the single SVI for management but I'll add a 2nd later today and see if that helps with the dhcp issue after I configure the helpers.  

[Scott Fella]

You should do on change at a time.  Configure the ip helper and see if that helps.  I don't think you need to configure an SVI on the 9800 for DHCP to work.

[mumbles202]

How would I create an ip-helper w/o the SVI?  For example I have the following configuration (vlan 10 is management, dhcp server resides on vlan 1, and clients will be on vlan 25):

vlan 10
 name Wireless_MGMT
!
vlan 20
 name Guest_Wireless
!
vlan 25
 name Staff_Wireless

interface TwoGigabitEthernet0/0/0
 switchport trunk allowed vlan 10,20,25
 switchport mode trunk
 negotiation auto
 no snmp trap link-status

interface Vlan10
 ip address 172.25.10.102 255.255.255.0 secondary
 ip address 172.25.10.101 255.255.255.0
 ip helper-address 172.25.1.25

[Scott Fella]

You are talking about creating an SVI on your L3 switch or router, not the 9800.  Also, be careful with secondary ip address as that has or might cause you issues also.

[marce1000]

                                     >.... I guess I'm still a little new to the 9800s .....
   - You can also and always have a checkup-review of your 9800 controller with the CLI command : show tech wireless , have the output analyzed with :   https://cway.cisco.com/wireless-config-analyzer/    , always advised  , also after configuration changes for instance , 

 M.
  

[mumbles202]

So after all this, we realized there was a problem w/ the upstream dhcp server so I'll be rolling back dhcp to be on the controller for that 1 SSID.  Can I just do this in the CLI like I'd do it on a router/L3 switch or do I need to configure the dhcp server in the GUI?

[Scott Fella]

You can do any configuration on the CLI, you will just need to know the commands and the order of those commands.  That can be found in the configuration guide.