In this article, we will introduce how PXE boot works.
Demo Environment:
Server 1: DHCP with WDS role IP address: 10.10.10.52
Server 2: WDS role IP address: 10.10.10.2
As this demo is based on a Hyper-V, legacy network adapter is required.
Scenario 1:
DHCP option 60, 66, 67 are not configured in this case.
Figure 1
In figure 1, we can see Frame Number 13, 14, 16, 17 are common DHCP packets during the communication with DHCP server.
And the frame 15 is another DHCP offer from WDS server. This packet contains important message, its own IP address and option 60—PXEClient. With the help of this Option, clients will boot up from server2.
Scenario 2:
If we install the WDS role on the same server with DHCP. DHCP option 60 is required, option 60: PXEClient.
Figure 2
In figure 2, we can see two handshakes. As mentioned in Scenario 1, there are four standard DHCP handshake, one DHCP offer from WDS, and the rests are PXE handshake via client port 68 and server side port 4011. More information about PXE handshake you can refer to this blog:
DHCP & PXE basics
http://blogs.technet.com/b/dominikheinz/archive/2011/03/18/dhcp-amp-pxe-basics.aspx
Worth mentioning here, as long as DHCP option 60 is configured, the client boots from server 1(WDS and DHCP) successfully, even if option 66 and 67 point to the wrong server or boot file.
Common issue
During the deployment we should be careful of the following:
1. Clients locate in a different subnet:
In this case, we should set IP helper on the router to point to WDS server and DHCP server. Port 4011 should be reachable on WDS server. Don’t forget your firewall.
2. PXE No reply from DHCP port 4011:
This error always bothers. We should verify the function on network layer as mentioned above. And if you configured to require administrator approval for unknown computers, you can try the following command:
WDSUTIL /delete-AutoAddDevices /devicetype:approveddevices
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