Sophos XG Firewall Windows DHCP Server not getting IP Addresses

I recently setup Sophos XG Firewall in my Home Lab and setup vlans, firewall rules, DHCP relays to point to my Windows DHCP Server, etc. The whole 9 yards. After I had everything working, I decided to add in the rest of my VLANS and create relays so they all worked without a hitch. After doing this, something that should not have effected other already working VLANs, nothing was getting DHCP addresses. Not even ones that was working.

I spent MANY hours trying to figure out why. I tried changing all of my firewall rules to any-any, etc. Nothing was working. After looing in the logs, I noticed this:

I was getting a block by the firewall rule 0 on Appliance Access as Denied. But why? A – it shouldn’t be a firewall rule blocking it because I put in an Any-Any rule. I tried changing everything. But it came down to one.. simple.. thing.. Here is my setup so you can understand the issue.

The Setup

  • VLAN 110 – 192.168.0.0/24 – Networking equipment
    • Sophos XG Firewall – IP 192.168.0.5
  • VLAN 111 – 192.168.1.0/24 – Servers
    • Windows AD/DNS/DHCP Server – 192.168.1.10
  • VLAN 112 – 192.168.2.0/24 Clients (No IP address)
    • Laptop
    • Cellphone

In Sophos, Windows DHCP, I setup DHCP subnets for all three vlans. Then in Sophos, I setup a DHCP relay just the Clients VLAN.

It worked! I was getting IP addresses assigned to the Clients.

The Issue

Then I decided to setup VLANs for every subnet and made quite a few other changes to get it to that perfect lab I was hoping for. I looked up and noticed all my Chromecasts was saying they couldn’t get an IP. I checked and sure enough, it was no longer dishing out IP addresses.

The Resolution

After much trial and error, I found that the fact I put a DHCP relay on the subnet the DHCP server was on, it was causing all the DHCP requests to fail.

Someone may have a better understanding of it and can explain better in the comments, but what my assumption is, when the DHCP request goes out, it gets blasted to the entire vlan to find a DHCP server by blasting out to port 67/68 UDP in search of a DHCP server. The gateway at 192.168.2.1 forwards this to the 192.168.1.0/24 vlan and it receives the blast on that subnet for the response, and blasts that back out to the requesting vlan.

If you put in a DHCP relay on the same subet as the DHCP server, then when it tries to “blast” the response back, the gateway takes that requests and tries to re-blast it in the same subnet. This causes a malformed loop and causes the request to fail. Thus removing the DHCP relay on the VLAN the DHCP server is in should fix this.

Please let me know if you have a better understanding of the cause or if this helps you!

Creating Rooms in Office 365 Exchange Online and Add To Rooms List

The title above is quite long, but exactly to the point – I found myself unsure how to add a resource room in Office 365 for Exchange online because it was set up by previous employees and hadn’t been done since then. Then I needed to add it to the Rooms List. I will walk you through my process of how I created a room and added it to a room list. This was also done in a hybrid environment (Exchange Online and Exchange 2013).

Create User Account

The first step is to create a regular AD user account. I created it in Active Directory User and Computers. You will not need to know the password, so set it to something crazy long and forget it. Be sure to set the password to never expires. And after all of this is said and done, we will disable the account for security.

I filled out Display Name, Telephone Number and Password Never Expires. Continue reading “Creating Rooms in Office 365 Exchange Online and Add To Rooms List”

Nothing happens when Compacting VHD in Hyper-V

For the past couple days now, I have been trying to compact a couple virtual machine hard drives VHDX via Hyper-V Manager. One of them worked without a hitch, however the other one I would go to Hyper-V manager, click edit disk and follow the normal procedures, but when I clicked finish, the box would just go away without it ever actually changing the size. I found a fix around this using a one line PowerShell command!

Continue reading “Nothing happens when Compacting VHD in Hyper-V”