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What is the Default IP Address Assigned if IAP DHCP Server hears no DHCPDiscover?

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  • 1.  What is the Default IP Address Assigned if IAP DHCP Server hears no DHCPDiscover?

    Posted Oct 07, 2016 12:15 PM
      |   view attached

    Hello!

     

    I have a single IAP-215 is setup as a standalone AP with a DHCP server (192.168.22.1 pool).

     

    I am have a client that is behaving in a silly way (client issue, not AP issue) where it sometimes does not send out a DHCP Discover.

     

    I have seen in the AP logs that the client successfully authenticates and associates and the client indicates a successful connection.  The client does show up in the AP clients table with an IP address of 192.168.3.1.

     

    I am assuming that the above is just a default IP address that is entered if the DHCP Discover isn't heard at all.  Is this correct? 

     

    Why would we not see an IP address of 0.0.0.0 instead?

     

    We have also seen one client switch from a valid IP address to a 192.168.6.1 address while 192.168.3.1 is in the client table.

     

    One of the ports on the system the AP is connected to is 192.168.3.1 so we ended up with an IP address conflict.  If the 192.168.3.1 is a default, is there any way we can change the default ip address assignment?

     

    What about when a lease time runs out?  Is the client removed from the table or does it get a new dummy IP address?

     

    The first solution is that the vendor needs to fix their client to properly send out a DHCP Discover, but I am trying to understand how the AP is expected to behave in this situation so we can anticipate possible other IP address conflicts.

     

    Regards,

    zummarius

    Attachment(s)

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    aplogs.txt   426 KB 1 version


  • 2.  RE: What is the Default IP Address Assigned if IAP DHCP Server hears no DHCPDiscover?

    Posted Oct 13, 2016 11:41 AM

    Any thoughts/ideas on where the 192.168.3.1 or 192.168.6.1 IP addresses might be coming from?

     

    Is this a default value assigned if a DHCPDiscover/Request/Renew is not heard from the client?  If yes, can this default subnet be specified?

     

    Regards,

    zummarius



  • 3.  RE: What is the Default IP Address Assigned if IAP DHCP Server hears no DHCPDiscover?

    EMPLOYEE
    Posted Oct 13, 2016 12:06 PM

    It is hard to say where it would be coming from.  Typically if a client does not get an ip address you would see 0.0.0.0



  • 4.  RE: What is the Default IP Address Assigned if IAP DHCP Server hears no DHCPDiscover?

    Posted Oct 14, 2016 12:53 PM

    Okay, would the ap logs have any indication?  I have the remote log server dumps (all log settings at "debug") that might indicate where the address is coming from?

     

    Vendor has already fixed the issue on their client, apparently their DHCP stack got stuck in a loop and would never issue the DHCP Discover.  Issues was silly, but glad it's fixed on their end.

    Now just curious about the odd IP address as there is port that already uses the address that got assigned to the client.  It would be helpful to understand in case this happens in the future.



  • 5.  RE: What is the Default IP Address Assigned if IAP DHCP Server hears no DHCPDiscover?
    Best Answer

    EMPLOYEE
    Posted Oct 14, 2016 01:14 PM

    You would turn on user debugging in syslog:

     

    syslog-level debug user-debug

     

     

    Your user debug information should then turn up in syslog. 

     

    You can also edit the SSID and under the security tab, you can enforce DHCP, which would not allow statically addressed clients to join.