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DHCP configuration on MC for Wireless SSID on Aruba OS 6.5

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  • 1.  DHCP configuration on MC for Wireless SSID on Aruba OS 6.5

    Posted Jan 18, 2022 11:53 AM
    Hi,

    I would like to ask how do we create DHCP for wireless SSID on Mobility Controller? Mobility Controllers currently are on version 6.5.4.
    Do we need to configure ip dhcp helper pointing to the mobility controller? Can the configuration works for branch and local deployment?

    Thanks in advance

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    DarrenPJW
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  • 2.  RE: DHCP configuration on MC for Wireless SSID on Aruba OS 6.5

    EMPLOYEE
    Posted Jan 18, 2022 12:59 PM
    What are you trying to do?  If you are supplying DHCP to your clients, your helper address on your VLAN should point to whatever DHCP server you have..

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    Any opinions expressed here are solely my own and not necessarily that of Hewlett Packard Enterprise or Aruba Networks.
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  • 3.  RE: DHCP configuration on MC for Wireless SSID on Aruba OS 6.5

    Posted Jan 18, 2022 01:15 PM
    Hi Joseph,

    I'm using the Mobility Controller as DHCP server for the wireless clients connecting using the SSID. Can you point to me how to configure this way?

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    DarrenPJW
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  • 4.  RE: DHCP configuration on MC for Wireless SSID on Aruba OS 6.5

    EMPLOYEE
    Posted Jan 18, 2022 02:43 PM
    If you give the mobility controller an ip interface in the VLAN you want to supply dhcp to, you would not need to provide a helper address (since the controller can see the broadcasts).  You would need to configure a dhcp scope (on the controller) in the same VLAN as the ip interface and make sure dhcp is enabled at the controller.

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    Any opinions expressed here are solely my own and not necessarily that of Hewlett Packard Enterprise or Aruba Networks.
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  • 5.  RE: DHCP configuration on MC for Wireless SSID on Aruba OS 6.5

    Posted Jan 18, 2022 03:29 PM
    Hi Joseph,

    If that's the case the IP interface configured in the same VLAN will be used as the gateway for the DHCP subnet? What if the gateway for the VLAN is at other devices, not on the mobility controller? 
    In addition, can the configuration mentioned works for branch deployment as well? 

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    DarrenPJW
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  • 6.  RE: DHCP configuration on MC for Wireless SSID on Aruba OS 6.5

    EMPLOYEE
    Posted Jan 18, 2022 05:19 PM
    Is the gateway for the client traffic another router?
    Does it already have a DHCP server?
    Then just bridge the client traffic from the controller to that VLAN and you are all set (either via a trunk or access port from the controller to the layer 3 switch).

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    Any opinions expressed here are solely my own and not necessarily that of Hewlett Packard Enterprise or Aruba Networks.
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  • 7.  RE: DHCP configuration on MC for Wireless SSID on Aruba OS 6.5

    Posted Jan 18, 2022 11:08 PM

    Hi Joseph,

    Yes, the gateway is on the core switches. However, customer insisted to have the DHCP server on the mobility controller instead. Can it be done? 

    If the gateway is on core switches and the DHCP server will be on the mobility controller, I will just need to configure ip dhcp helper on the gateway pointing it to the mobility controller's IP interface of the VLAN where the client will reside right?



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    DarrenPJW
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  • 8.  RE: DHCP configuration on MC for Wireless SSID on Aruba OS 6.5

    EMPLOYEE
    Posted Jan 19, 2022 06:50 AM
    If the gateway is on the switch, and the controller is trunked to the VLAN, AND has an ip interface on that VLAN, the controller's dhcp server will assign ip addresses on that VLAN.   

    I would say that it is a best practice to have an external DHCP server except for maybe a small guest WLAN.  The need for clustering, and/or redundancy will necessitate an external dhcp server.  That should be done ahead of time to avoid growing pains in the future.  The dhcp scope and reservations on a controller are not synchronized with any other controllers, so if that controller with  the dhcp server is disconnected from the network, no new clients will be able to obtain ip addresses.  Maintaining multiple dhcp servers on controllers with a split scope is an administrative burden and will make troubleshooting much more difficult.

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    Any opinions expressed here are solely my own and not necessarily that of Hewlett Packard Enterprise or Aruba Networks.
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  • 9.  RE: DHCP configuration on MC for Wireless SSID on Aruba OS 6.5

    Posted Jan 20, 2022 12:03 AM
    Hi Joseph,

    Noted. Thanks for the feedback. So is not necessary for me to configure the ip helper on the gateway with the VLAN ip interface on the controller? 
    In regards to the redundancy that you mentioned, the dhcp scope and reservations on the primary controller will not sync across the secondary controller, despite any HA setup in place?

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    DarrenPJW
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  • 10.  RE: DHCP configuration on MC for Wireless SSID on Aruba OS 6.5

    EMPLOYEE
    Posted Jan 20, 2022 08:09 AM
    If the controller has an ip interface in the VLAN and it has a dhcp scope configured, it will distribute ip addresses.

    DHCP scopes and reservations are not synchronized, no.

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    Any opinions expressed here are solely my own and not necessarily that of Hewlett Packard Enterprise or Aruba Networks.
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  • 11.  RE: DHCP configuration on MC for Wireless SSID on Aruba OS 6.5

    MVP
    Posted Jan 19, 2022 07:34 AM
    I do NOT recommend using the DHCP server for clients except, perhaps for extremely small, temporary deployments. the controller DHCP server is just meant for testing environments, not for production use. We do use the controller DHCP server to provide an inner ip address to our Remote APs.

    We found that out the hard way when we used a controller DHCP server for our guest clients. When the controller ran out of resources it took two people working closely together to be able to get things operational again until we moved DHCP to a proper server.

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    Bruce Osborne ACCP ACMP
    Liberty University

    The views expressed here are my personal views and not those of my employer
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