UEFI pxe boot problem from a network

[lebrun78]

In
UEFI Reading the DHCP offer on boot, router ip et subnet mask are wrong. (ip router and subnet mask of the vlan of fog server).

In legacy mode, (same PC, same vlan)
router ip et subnet mask are wrong too. (ip router and subnet mask of the vlan of fog server). But the boot is going on
capturedhcp.txt

[george1421]

@lebrun78 would you upload the entire pcap. I need to see the raw data and not just the packet headers.

[lebrun78]

here is a uefi capture:

capturedhcp.pcap

[george1421]

@lebrun78 Please look at the forum chat (chat bubble at the top of the forum window) for a few questions based on the pcap.

[Sebastian Roth]

@lebrun78 said in UEFI pxe boot problem from a network:

router ip et subnet mask are wrong

I think this is key to the mystery here!

[george1421]

@Sebastian-Roth I agree, also in the pcap it has the bootp pxe boot information (in the header) but not the dhcp pxe boot options (66 & 67). Some target systems look at the ethernet header and others look at the dhcp options to boot.

I didn’t try to figure out the funky subnet mask (255.255.248.0) to make sure all of the subnets defined were in range. I figured everything was close enough it should work.

[lebrun78]

Several vlan:

• 148.60.0.0 255.255.248.0 (148.60.0.0 > 148.60.7.255)
  (fog server vlan 148.60.4.1, dhcp 148.60.4.3 router 148…60.7.254

• 148.60.8.0 255.255.255.0 (148.60.8.0 > 148.60.8.255)
  router 148…60.8.254 no dhcp

• 148.60.10.0 255.255.255.0 (148.60.10.0 > 148.60.10.255)
  dhcp 148.60.10.252 router 148…60.10.254 (vlan with deployment problem)

• 148.60.11.0 255.255.255.0 (148.60.11.0 > 148.60.11.255)
  dhcp 148.60.11.248 router 148…60.11.254

• 148.60.12.0 255.255.255.0 (148.60.12.0 > 148.60.12.255)
  dhcp 148.60.11.252 router 148…60.12.254

• 148.60.13.0 255.255.255.0 (148.60.13.0 > 148.60.13.255)
  dhcp 148.60.13.248 router 148…60.13.254

• 148.60.14.0 255.255.255.0 (148.60.14.0 > 148.60.14.255)
  dhcp 148.60.14.252 router 148…60.14.254

• 148.60.15.0 255.255.255.0 (148.60.15.0 > 148.60.15.255)
  dhcp 148.60.15.109 (its native vlan) router 148…60.15.254

[lebrun78]

@george1421
Here is the capture from fog server, client in uefi mode
uefi.pcap

[george1421]

@lebrun78 Well I’m not sure how to explain this situation but @Sebastian-Roth is spot on.

First the easy part, it appears there are 2 dhcp servers (or configurations) involved here. The reason why I say that is that they are giving different responses to the pxe boot request. If you look at the pcap on the working subnet it responds with dhcp option 12, the not working pcap does not include dhcp option 12. This is only important to show there are different settings for these two pcaps.

Now to the hard part to explain.

On the working subnet
Client IP: 148.60.3.152
Subnet Mask: 255.255.248.0
Gateway: 148.60.7.254
Subnet Range: 148.60.0.1-148.60.7.254

On the not working subnet.
Client IP: 148.60.10.193
Subnet Mask: 255.255.248.0
Gateway: 148.60.7.254
Subnet Range: 148.60.8.1-148.60.15.254

So now to identify the problem. If you look at the not working subnet you will see the gateway IP address is outside of the usable range of the client’s IP address. The gateway address is 148.60.7.254 but the subnet base address is 148.60.8.0. So its not possible for the client to reach the router to get outside of the subnet to connect to the FOG server at 148.60.4.1. At this time the problem is infrastructure related and not FOG.

[lebrun78]

@george1421
“At this time the problem is infrastructure related and not FOG.” I agree.
I don’t understand the boot dhcp response on vlan 10.
The ip configuration is good when loaded !

[Sebastian Roth]

@lebrun78 said in UEFI pxe boot problem from a network:

The ip configuration is good when loaded !

You mean when Windows boots it’s correct?

[george1421]

@lebrun78 said in UEFI pxe boot problem from a network:

I don’t understand the boot dhcp response on vlan 10.

Looking at the dhcp packet from your main dhcp server its giving out the wrong default router address for this subnet. So any computer that uses dhcp should not be able to connect to any device beyond its local subnet. Its impossible since the router its being told to use to leave the local subnet, is on a different subnet to start with.

You should contact your infrastructure staff and ask they to confirm the dhcp settings are correct for this subnet. If I had to guess, I would think they just copied the settings from the subnet where your FOG server is and pasted them into the vlan 10 subnet configuration and missed the router value. But that is only a guess made from 6600km away.

[lebrun78]

@Sebastian-Roth
Yes ipconfig is good.

[lebrun78]

@george1421
I’m the infrastructure manager, the dhcpd.conf is the one in the first post …

[george1421]

@lebrun78 I’m going to have to look into this, but I have to ask the question why does the dhcp servers have two different IP addresses? Those each are listed in the pcaps.

[lebrun78]

This post is deleted!

[lebrun78]

@george1421

Yes, we don’t have dhcp relay, the dhcp server have several virtual network interface, one on each vlan.

[george1421]

@lebrun78 I can’t see from the config how/why its sending out the wrong router address unless something in include "/etc/dhcp/vip.conf"; is doing it.

Wait, there is something strange going on here. Look at the base address and the subnet mask as defined.

subnet 148.60.10.0 netmask 255.255.255.0 {
##########################################
option domain-name-servers 148.60.15.109,148.60.15.106 ;
option domain-name "istic.univ-rennes1.fr" ;
option routers 148.60.10.254 ;
option subnet-mask 255.255.255.0 ;
default-lease-time 600 ;
max-lease-time 1200 ;

group {
# On commente les deux lignes suivantes pour éviter le menu de Fog
        next-server 148.60.4.1;

But look at the pcap what the client is being told.

As you see in the picture the client is being told that its subnet mask is 255.255.248.0, but your config files says 255.255.255.0. The client is being told the router is 148.60.7.254 but your config file says 148.60.10.254.

So I’ll ask you the same question again in a different way. Is dhcp server 148.60.10.252 and 148.60.4.3 the same computer? If it is do you have 2 different instances of isc-dhcp server running, where each instance is bound to a different network interface? Something is strange with the 148.60.10.252 dhcp server.

[lebrun78]

@george1421

So I’ll ask you the same question again in a different way. Is dhcp server 148.60.10.252 and 148.60.4.3 the same computer?
YES
I have only one dhcpd.conf file, sone only one instance of dhcp

Here is what I get on the same machine on vlan 148.60.10.0/24 when windows is loaded:

It’s crazy, no ?

[lebrun78]

I have made 2 boot on the windows machine, UEFi pxe boot and hard drive boot.
I get this logs in my dhcp server:

Apr  6 09:46:02 sybille2 dhcpd: PXEClient:Arch:00007:UNDI:003016
Apr  6 09:46:02 sybille2 dhcpd: DHCPDISCOVER from 10:65:30:83:5c:4b via em2.10
Apr  6 09:46:03 sybille2 dhcpd: DHCPOFFER on 148.60.10.198 to 10:65:30:83:5c:4b via em2.10
Apr  6 09:46:05 sybille2 dhcpd: PXEClient:Arch:00007:UNDI:003016
Apr  6 09:46:05 sybille2 dhcpd: DHCPREQUEST for 148.60.10.198 (148.60.10.252) from 10:65:30:83:5c:4b via em2.10
Apr  6 09:46:05 sybille2 dhcpd: DHCPACK on 148.60.10.198 to 10:65:30:83:5c:4b via em2.10
Apr  6 09:46:41 sybille2 dhcpd: MSFT 5.0
Apr  6 09:46:41 sybille2 dhcpd: DHCPDISCOVER from 10:65:30:83:5c:4b via em2.10
Apr  6 09:46:42 sybille2 dhcpd: DHCPOFFER on 148.60.10.190 to 10:65:30:83:5c:4b (MININT-S9D1BSU) via em2.10
Apr  6 09:46:42 sybille2 dhcpd: MSFT 5.0
Apr  6 09:46:42 sybille2 dhcpd: DHCPREQUEST for 148.60.10.190 (148.60.10.252) from 10:65:30:83:5c:4b (MININT-S9D1BSU) via em2.10
Apr  6 09:46:42 sybille2 dhcpd: DHCPACK on 148.60.10.190 to 10:65:30:83:5c:4b (MININT-S9D1BSU) via em2.10
Apr  6 09:46:42 sybille2 dhcpd: Unable to add forward map from MININT-S9D1BSU.istic.univ-rennes1.fr to 148.60.10.190: not found

The same machine gets to differents IP, 148.60.10.190 and 148.60.10.198 at 09:46:03 (pxe booot) and at 09:46:40