Boot Server and DHCP server on the same system.

Document ID : KB000027520
Last Modified Date : 14/02/2018
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Summary:                              

When a DHCP server and a Boot Server are running on the same machine, then the DHCP server uses the port 67. After having received a DHCP discover from the PXE client, a DHCP offer will be send by the DHCP server to the PXE client.

But the Boot Server cannot use port 67 and does not send an additional DHCP offer with the PXE Boot Server information to the PXE client. So the PXE client does not receive the necessary PXE boot information.

 

Environment:                                              

CA Client Automation - All Versions

 

Instructions:

This problem can be solved when the DHCP offer of the DHCP server contains additionally the PXE boot information of the Boot Server.
The DHCP offer of the DHCP server must contain
  1. option 60:

  2. option 43: with the suboptions 6, 8, 9, 10, 71
After the PXE client has received an ip address from the DHCP server, the PXE client should send a DHCP Request to the specified Boot Server
(in option 43:Suboption 8: PXE boot servers) to get the boot image file name.

example: DHCP offer

    Option 53: DHCP Message Type = DHCP Offer 
    Option 54: Server Identifier = 192.168.111.131 
    Option 60: Vendor class identifier = "PXEClient" 
    Option 97: UUID/GUID-based Client Identifier (17 bytes) 
    Option 43: Vendor-Specific Information (PXEClient) 
        Suboption 6: PXE discovery control = 2 
        Suboption 8: PXE boot servers (7 bytes) 
        Suboption 9: PXE boot menu (38 bytes) 
        Suboption 10: PXE menu prompt (24 bytes) 
        Suboption 71: PXE boot item (4 bytes) 
        End PXEClient option 
    End Option 
    option 43 in detail: 
    2b 55 06 01 02 08 07 00 07 01 c0 a8 6f 83 09   +U..........o.. 
    26 00 07 23 43 41 2d 55 6e 69 63 65 6e 74 65 72  &..#CA-Unicenter 
    20 4d 61 6e 61 67 65 64 50 43 20 42 6f 6f 74 20   ManagedPC Boot 
    53 65 72 76 65 72 00 0a 18 00 50 72 65 73 73 20  Server....Press 
    46 38 20 74 6f 20 76 69 65 77 20 6d 65 6e 75 00  F8 to view menu. 
    2e 47 04 00 08 00 00 ff                          .G...... 

(in this example c0 a8 6f 83 is the ip address of the SD boot server.)

NOTE:

  • The Detail of option 43 above shows the complete hex string of the option. When defining the value of option 43 do not include the first 2 bytes (2b 55) as these are added by the DHCP server. (2b is the descriptor for option 43 and 55 is the length).

  • the DHCP offer should not contain option 67: boot file name

  • Option 60 is not a standard option and must be manually added using netsh.exe
    Adding DHCP option 60 to Windows 2000 or higher DHCP server:
    1. Open a command window (select START->RUN->CMD)

    2. Type netsh

    3. Type dhcp

    4. Type server \\servername *OR* server ip_address

    5. You should then see a command prompt that says: dhcp server>

    6. Type add optiondef 60 PXEClient STRING 0 comment=option added for PXE support

    7. Type set optionvalue 60 STRING PXEClient

    8. To confirm everything has been set correctly, type show optionvalue all)