Wireless Access

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Traffic Flow From Client to Conteroller

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  • 1.  Traffic Flow From Client to Conteroller

    Posted Dec 02, 2011 07:40 AM

    i have a question regardingh Traffic Flow from Client to Controller , i need to know about IP addresses

    let's assume that a wireless client needs to access internet : Client > AP > Controller > Internet Router 

    *Client to AP : srcip = client , dst ip = AP

    *AP to Controller : encapsulates the above into GRE packet & sends to controller , srcip=AP , dst ip = controller

    *Controller to Internet Router : Controller decapsulates the above packet & send to interner router  , my question is does the controller send the packet a( after depasulation ) with src-ip = original ip ( client )  or with src ip = controller 

     



  • 2.  RE: Traffic Flow From Client to Conteroller
    Best Answer

    EMPLOYEE
    Posted Dec 02, 2011 07:44 AM

    On the user VLAN, if the controller has "ip nat inside" (source nat) on the VLAN, the source ip address will be the controller.  If ip nat inside is not checked on the controller, the source ip address will be the ip address that the user received.

     



  • 3.  RE: Traffic Flow From Client to Conteroller

    Posted Dec 02, 2011 07:53 AM

    Thanks 



  • 4.  RE: Traffic Flow From Client to Conteroller

    Posted Dec 02, 2011 08:01 AM

    So , If i'm using External DHCP Server & the Client sent its DHCP request the below will happen :

    DHCP request ( broacast ) will be sent to AP , AP will encapsulate & sent to Controller  , Controller will decapsulate & i will find itis a brodcast request 

    do i need to configure DHCP Rely on my controller in this case ? if not what will happen after the last step above ?

     

     



  • 5.  RE: Traffic Flow From Client to Conteroller

    Posted Dec 02, 2011 08:06 AM

    The layer-3 interface that the wireless client belongs to needs an IP address and an "ip helper x.x.x.x" statement defined.  When the DHCP broadcast arrives at the VLAN interface where the user belongs on the controller, the ip helper will forward the DHCP request to the address defined by the "ip helper" statement and put it's own VLAN IP address in the request.  That way, when the DHCP server gets the request, it can deteremine what subnet to allocate the address from.



  • 6.  RE: Traffic Flow From Client to Conteroller

    EMPLOYEE
    Posted Dec 02, 2011 08:06 AM

    You do not need to configure a relay or "ip helper-address" on the controller if:

     

    - The default gateway of the client VLAN already has an ip address

    - The DHCP server is on the same VLAN as the client VLAN

    - The controller is providing DHCP server for the client VLAN

     

    If the above 3 are not the case, you need to make sure:

     

    - The controller has an ip interface on that VLAN, AND you put a helper-address on that IP interface pointing to the DHCP server or

    - The controller is bridging traffic to a VLAN that already has a helper address configured or

    - The DHCP server is on the same VLAN as the client.