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is DHCP Client ip address 0.0.0.0 or 169.254.x.y ?

    Question

  • hi al

    in 70-642 R2 self-paced training kit , on page 256 we see that dhcp client ip address is always stated and shown as 0.0.0.0

    but as we know, dhcp client if havn't been able to contact dhcp server , assign itself from APIPA Range ( 169.254.x.y /16 )

    so why it's ip address is always shown as 0.0.0.0 in this book ?

    thanks 

    Wednesday, October 19, 2011 3:53 AM

Answers

  • Hi,

    APIPA is a DHCP failover mechanism. With APIPA, DHCP clients can obtain IP addresses when DHCP servers are nonfunctional. APIPA exists in all popular versions of Windows except Windows NT. When a DHCP server fails, APIPA allocates addresses in the private range 169.254.0.1 to 169.254.255.254. Clients verify their address is unique on the LAN using ARP. When the DHCP server is again able to service requests, clients update their addresses automatically.

    In APIPA, all devices use the default network mask 255.255.0.0 and all reside on the same subnet.

    APIPA is enabled on all DHCP clients in Windows unless the computer's Registry is modified to disable it. APIPA can be enabled on individual network adapters.

    I do not have copy of the 70-642 R2 self-paced training kit but I think its a typing mistake, it should be APIPA.

    Hope this helps.

    Regards,
    Abhijit Waikar.
    -------------------------------
    MCSA|MCSA:Messaging|MCTS|MCITP:SA
    My Blog: http://abhijitw.wordpress.com
    This posting is provided AS IS with no warranties, and confers no rights.

    Wednesday, October 19, 2011 4:07 AM

All replies

  • Hi,

    APIPA is a DHCP failover mechanism. With APIPA, DHCP clients can obtain IP addresses when DHCP servers are nonfunctional. APIPA exists in all popular versions of Windows except Windows NT. When a DHCP server fails, APIPA allocates addresses in the private range 169.254.0.1 to 169.254.255.254. Clients verify their address is unique on the LAN using ARP. When the DHCP server is again able to service requests, clients update their addresses automatically.

    In APIPA, all devices use the default network mask 255.255.0.0 and all reside on the same subnet.

    APIPA is enabled on all DHCP clients in Windows unless the computer's Registry is modified to disable it. APIPA can be enabled on individual network adapters.

    I do not have copy of the 70-642 R2 self-paced training kit but I think its a typing mistake, it should be APIPA.

    Hope this helps.

    Regards,
    Abhijit Waikar.
    -------------------------------
    MCSA|MCSA:Messaging|MCTS|MCITP:SA
    My Blog: http://abhijitw.wordpress.com
    This posting is provided AS IS with no warranties, and confers no rights.

    Wednesday, October 19, 2011 4:07 AM
  • hi al

    in 70-642 R2 self-paced training kit , on page 256 we see that dhcp client ip address is always stated and shown as 0.0.0.0

    but as we know, dhcp client if havn't been able to contact dhcp server , assign itself from APIPA Range ( 169.254.x.y /16 )

    so why it's ip address is always shown as 0.0.0.0 in this book ?

    thanks 

    When First  client communicate  with DHCP server have addres 0.0.0.0 than if client is set to get DHCP address but DHCP is OFF he get 169.254.x.y/16
    Wednesday, October 19, 2011 7:53 AM