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DHCP Scope Options for PXE on swtiches RRS feed

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    Hello,

    I am trying to get PXE support for OSD in a sccm 2012 environment.

    WSD resides on the same server as my SCCM 2012 Primary server.

    I currently have one dp with PXE enabled.

    My networking team asked what I needed for PXE support.

    I responded:

    DHCP discover package contains option 60

    DHCP discover uses port 67 UDP

    DHCP Offer uses port 68 UDP

    Server ack from PXE server including options 66 and 67

    Client unicast request for options 66 (boot server) and option 67 (boot file) (port 4011 UDP)

    They responded with what do I need from below

     The above response was from a different job and location. Now they are asking for info on boot file and hostname.  Hostname I would think be the dp or in our case, the sccm primary server.  The boot file, I have no idea

    Thanks so much for your help,

    Mark

    • Edited by Mlhend2002 Friday, January 23, 2015 5:18 PM
    Friday, January 23, 2015 5:11 PM

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    Ok, networking agrees to use IPhelpers, but needs "official documentation" of exactly what to do.  Does anyone have a link that I may give to network to use.  I really do appreciate it.  I never thought I would have to do the network part for them. :(

    Thanks, 

    Mark

    The general gist is that your router interfaces need to relay/forward bootp/dhcp "discover" & "request" to *both* your DHCP and your PXE-enabled DP.
    This will cause the DHCP-client's discover/requests to be relayed to both, but the PXE-enabled DP won't respond to the initial discover/request because it can't issue IP addresses.
    But once the client *does* have an IP address, and it issues a PXE request, the PXE request will be relayed to both, the DHCP server will ignore it but the PXE-enabled DP will process it and offer the NBP and then the TFTP of the boot image etc.

    This is recommended/preferred over using DHCP options 66/67.

    It's recommended in lots of places, but here's a great reference:
    http://blogs.technet.com/b/system_center_configuration_manager_operating_system_deployment_support_blog/archive/2011/10/14/troubleshooting-the-pxe-service-point-and-wds-in-configuration-manager-2007.aspx

    For "official documentation" on how to configure the router, the router manufacturer will help with that.

    Cisco refer to their implementation as "ip helper-address", which is why the feature is often referred to as "iphelpers".

    Don
    (Please take a moment to "Vote as Helpful" and/or "Mark as Answer", where applicable.
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    • Proposed as answer by Daniel JiSun Thursday, January 29, 2015 8:27 AM
    • Marked as answer by Daniel JiSun Monday, February 2, 2015 10:42 AM
    Saturday, January 24, 2015 11:34 AM
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    Hi,

    DHCP option 60 should be enabled when WDS and DHCP on the same server. Since you are not using windows DHCP server, as Jason suggested, just do not use DHCP option. In addition, IP helper should also pointed to PXE server.

    Please remember to mark the replies as answers if they help and unmark them if they provide no help. If you have feedback for TechNet Subscriber Support, contact tnmff@microsoft.com.

    • Proposed as answer by Daniel JiSun Thursday, January 29, 2015 8:27 AM
    • Marked as answer by Daniel JiSun Monday, February 2, 2015 10:42 AM
    Sunday, January 25, 2015 6:11 AM

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    Ultimately, this has nothing to do with ConfigMgr.

    Note though a better answer to the network team would have been that you need iphelpers on the layer 3 devices pointing to the WDS server.

    DHCP scope options can be problematic and generally aren't recommended as the first choice for PXE. Additionally, when you start PXE booting UEFI systems, DHCP scope options become even more problematic.

    Jason | http://blog.configmgrftw.com | @jasonsandys

    • Proposed as answer by Jeff Poling Friday, January 23, 2015 5:49 PM
    Friday, January 23, 2015 5:41 PM
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    Networking response:

    Iphelpers are already defined on the L3 devices to point to the DHCP servers. The SCCM server shouldn’t be giving out DHCP ip addressing, correct? 

    Friday, January 23, 2015 5:59 PM
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    You can have an additional IP helper point to the PXE server as well.  Clients will still get DHCP address from your DHCP server(s) but then boot from the PXE server based on the IP helper for that server.

    Jeff

    Friday, January 23, 2015 6:02 PM
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    Networking response:

    Iphelpers are already defined on the L3 devices to point to the DHCP servers. The SCCM server shouldn’t be giving out DHCP ip addressing, correct? 


    They need to point to the CM server. It's a relay basically.

    John Marcum | Microsoft MVP - Enterprise Client Management
    My blog: System Center Admin | Twitter: @SCCM_Marcum | Linkedin: John Marcum

    Friday, January 23, 2015 6:04 PM
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    From Networking: I can’t point all the DHCP IPhelper addresses to anything but a high-availability appliance as it is setup today, that’s not a good structure.

    Talk about stubborn Network team. Maybe I have to go back to plan A, but don't know what the info on the boot file would be.

    Thanks,

    Mark

    Friday, January 23, 2015 6:35 PM
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    Their exisitng config stays in place.  They just need to add one more IP Helper to point to your PXE server.  They are not changing the IP helpers that exist for DHCP servers.

    Jeff

    Friday, January 23, 2015 6:49 PM
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    Ok, networking agrees to use IPhelpers, but needs "official documentation" of exactly what to do.  Does anyone have a link that I may give to network to use.  I really do appreciate it.  I never thought I would have to do the network part for them. :(

    Thanks, 

    Mark

    Friday, January 23, 2015 7:46 PM
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    As mentioned, PXE really has nothing to do with ConfigMgr or Microsoft even. It's a NIC and network task. Thus, you'll need to go hunt up official network documentation for your network vendor. There are various documents from Microsoft recommending things to do, but ultimately, as mentioned, it's a network configuration and thus specific to your network gear. I'm not familiar with Cisco documentation anymore (assuming that's your vendor) so I can't provide anything there.

    To address some of the other comments above, protocol wise, DHCP and PXE use the exact same protocol. Requests sent by the NIC, called DHCP Discover have a single flag difference that say I want a DHCP server or I want a PXE server. Your WDS server does not provide ip addresses at all. Thus, as indicated by Jeff, you need *additional* iphelpers added to provide PXE functionality across subnets. Existing iphelpers used for DHCP are not affected in any way.

    As for your network team, well, honestly, that's par for the course.

    Jason | http://blog.configmgrftw.com | @jasonsandys

    Friday, January 23, 2015 8:23 PM
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    Ok, networking agrees to use IPhelpers, but needs "official documentation" of exactly what to do.  Does anyone have a link that I may give to network to use.  I really do appreciate it.  I never thought I would have to do the network part for them. :(

    Thanks, 

    Mark

    The general gist is that your router interfaces need to relay/forward bootp/dhcp "discover" & "request" to *both* your DHCP and your PXE-enabled DP.
    This will cause the DHCP-client's discover/requests to be relayed to both, but the PXE-enabled DP won't respond to the initial discover/request because it can't issue IP addresses.
    But once the client *does* have an IP address, and it issues a PXE request, the PXE request will be relayed to both, the DHCP server will ignore it but the PXE-enabled DP will process it and offer the NBP and then the TFTP of the boot image etc.

    This is recommended/preferred over using DHCP options 66/67.

    It's recommended in lots of places, but here's a great reference:
    http://blogs.technet.com/b/system_center_configuration_manager_operating_system_deployment_support_blog/archive/2011/10/14/troubleshooting-the-pxe-service-point-and-wds-in-configuration-manager-2007.aspx

    For "official documentation" on how to configure the router, the router manufacturer will help with that.

    Cisco refer to their implementation as "ip helper-address", which is why the feature is often referred to as "iphelpers".

    Don
    (Please take a moment to "Vote as Helpful" and/or "Mark as Answer", where applicable.
    This helps the community, keeps the forums tidy, and recognises useful contributions. Thanks!)

    • Proposed as answer by Daniel JiSun Thursday, January 29, 2015 8:27 AM
    • Marked as answer by Daniel JiSun Monday, February 2, 2015 10:42 AM
    Saturday, January 24, 2015 11:34 AM
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    As the guys say the configuration is vendor specific but it's the same configuration for DHCP and PXE

    Here is an example from a Cisco device:

    interface Vlan10 

       ip address 172.16.112.254 255.255.255.0

       ip helper-address 172.16.1.1

    End


    This allows clients booting in 172.16.112.0/24 subnet to find the WDS server (172.16.1.1).

    Gerry Hampson | Blog: www.gerryhampsoncm.blogspot.ie | LinkedIn: Gerry Hampson | Twitter: @gerryhampson

    Saturday, January 24, 2015 1:53 PM
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    Actually let's go one step further and make it really simple for your colleagues.

    interface Vlan10

       ip address 172.16.112.254 255.255.255.0

       ip helper-address 172.16.1.1

       ip helper-address 172.16.1.2

    End

    This allows clients booting in 172.16.112.0/24 subnet to find the WDS server (172.16.1.1) and the DHCP server (172.16.1.2). The IP Helpers do not interfere with each other as explained by Jason above. You will have to carry out this configuration in each VLAN in which you require PXE booting.

    Gerry Hampson | Blog: www.gerryhampsoncm.blogspot.ie | LinkedIn: Gerry Hampson | Twitter: @gerryhampson

    Saturday, January 24, 2015 2:17 PM
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    Hi,

    DHCP option 60 should be enabled when WDS and DHCP on the same server. Since you are not using windows DHCP server, as Jason suggested, just do not use DHCP option. In addition, IP helper should also pointed to PXE server.

    Please remember to mark the replies as answers if they help and unmark them if they provide no help. If you have feedback for TechNet Subscriber Support, contact tnmff@microsoft.com.

    • Proposed as answer by Daniel JiSun Thursday, January 29, 2015 8:27 AM
    • Marked as answer by Daniel JiSun Monday, February 2, 2015 10:42 AM
    Sunday, January 25, 2015 6:11 AM