Client wont boot via PXE and WDS [Resolved]

Question

So the past couple of weeks I've been trying to get our WDS running again. The person who set the WDS up doesn't work here anymore and very little is documented about it. I managed to get the majority of the problems out of the way that I had on the server itself, now I'm trying to boot a client over PXE but I keep running into errors with several DHCP Setups I came across on Google and Technet.

We use cloud managed Meraki switches and have a VLAN set up on the switch the client is hooked up on (specifialy for PXE Boots). The WDS and DHCP Server are in the same subnet/VLAN but in a different one than the client. The WDS is a Windows 2012R2 and the client is a DELL Optiplex 790.

The way the VLAN for the client was setup originaly it ran a DHCP with the Nameservers specified and DHCP Options enabled (boot server, boot file and option 60 set to PXEClient (String)). Using this setup the client got an IP from the DHCP but then returned the PXE-E55 error that he did not get a reply from the proxy DHCP on port 4011. I tried several other things like removing option 60 but there it doesn't even give me an error code, it just shows the IP, Mask, DHCP and Gateway, says "TFTP." and then just exits the boot agent. I even updated the BIOS just to be sure that it wasn't an issue.

By now my basic knowledge is used up and none of the solutions I found on the web helped.

Does anyone have any tips or expirience with similar problems who could get me on the right track to narrow down the problem?

Thank you all in advance!

EDIT: Okay since I'm new to this network and the job, I just found out that the DHCP is on the switch and per VLAN we have a DHCP each. Meaning that the WDS has it's own DHCP it's comunicating with, as well as the PXE Client has it's own DHCP to comunicate with. But WDS and DHCP are not on the same server.

Solution

A PXE environment can have 2 basic layouts.

1. A single DHCP server providing both IPs and PXE info
2. A DHCP server providing IPs and a proxyDHCP on a different PC providing "only" PXE info on a complementary DHCP transaction on port 4011.

Despite the implemented scenario if client and DHCP/proxyDHCP servers are located in different networks the intermediate routing gear must have the DHCP relay capabilities (IP Helpers) "ON" in order to forward the otherwise blocked DHCP broadcast traffic.

For really knowing what's going on just run a traffic capture with Wiershark and follow the very simple DORA (DISCOVER-OFFER-REQUEST-ACK) DHCP traffic sequence.

Comments

[Admin]

proxyDHCP and DHCP relay (AKA IP Helper) are two completely different animals; please read.

[Admin]

you are still lost. IP relay capabilities cannot be "configured" on proxyDHCP services. A DHCP relay is in charge of forwarding DHCP broadcast traffic from one to another network (this service is usually provided by routing gear). A proxyDHCP is a DHCP server that does not provide IPs; it provides PXE info, "only" to PXE clients. A proxyDHCP is the non-intrusive way to offer PXE services when you are not able to alter your already in-place DHCP infrastructure.

[Admin]

Okay since I'm new to this network and the job, I just found out that the DHCP is on the switch and per VLAN we have a DHCP each. Meaning that the WDS has it's own DHCP it's comunicating with, as well as the PXE Client has it's own DHCP to comunicate with. But WDS and DHCP are not on the same server.

[Admin]

you must confirm you have only one DHCP server per segment providing IPs and set WDS as proxyDHCP providing only PXE info (TFTP server IP and name of the NBP) but no IPs

[LM31]

So the WDS, when on a different server from the DHCP, should use the DORA sequence with the client too?

[Pat]

if you have an external DCP server only providing IPs then "someone else" must provide the proxyDHCP services bringing the PXE info to the client also using a DORA sequence. i.e the WDS server