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Clients don't receive an IP address from DHCP on newly created VLAN

Hi! I just created a new VLAN and DHCP server with firewall rule and clients are not able to get an IP address. My goal is to have my guest WIFI network (and if I can get this working, my IoT network) on a separate VLAN. I've restarted my switch, firewall, and DHCP server, removed and re-created everything a few times but no joy.

My newly created VLAN interface:

My new network IP host:

My newly created DHCP server on the firewall for the new VLAN:

The new firewall rule to allow traffic from the network to the WAN (placed in top position):

I have a Unifi AP connected but have also tried a wired laptop to another dedicated VLAN port on the switch with the same results: can't get an IP address

Thanks for any help!

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  • Hello there,

    Thank you for contacting the Sophos Community.

    I see in your other post you have the same VLAN configured for a different purpose, make sure you are not overlapping the subnets! 


    Emmanuel (EmmoSophos)
    Technical Team Lead, Global Community Support
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  • No this is for a different site. I'm just using the same VLAN 200 for all my sites for guest wifi networks.

  • Hi dsurfer ,

    Tcpdump will help us to find whether the request reaches Firewall or not from the switch

    console> tcpdump interface PortA.200  'port 67 or 68 

    09:12:51.593198 PortA.200, IN: IP > BOOTP/DHCP, Request from 50:22:00:06:00:00, length 300

    If no IN packet is received with the above tcpdumps, we need to confirm from the switch VLAN configuration and VLAN interface are properly set on the switch.

    tcpdump command : 

    tcpdump interface <interface> 'port <port-number>'

    Thanks and Regards

    "Sophos Partner: Infrassist Technologies Pvt Ltd".

    If a post solves your question please use the 'Verify Answer' button.

  • There doesn't seem to be anything when checking:

  • Please share a screenshot of your network topology (router/firewall, switches, clients / servers).
    Is the uplink from switch to firewall correctly tagged / untagged with the said VLAN?

    Also share informations with your interface settings - vlans, ips, ports on the firewall and switch.


    Sophos SG 210 with Sophos XG Home - 19.5 GA

    If a post solves your question please use the 'Verify Answer' button.

  • looks like IP helpers are missing on the switches so the Request does not reach the Firewall. at least not on the VLAN interface.

    Restart the tcpdump for PortA without VLAN 200.

    tcpdump interface PortA  'port 67 or 68 -n

  • Please check with other managed switch, as you have issues with the switch end.

    below is the configuration of the working switch.


    "Sophos Partner: Infrassist Technologies Pvt Ltd".

    If a post solves your question please use the 'Verify Answer' button.

  • So I did get some results when excluding the VLAN from the filtering: 

  • The weird thing is that I have it set up pretty much exactly the same as another one of my sites and it still doesn't work. The same Sophos firewall system, same Datto switch manufacturer. All trunk ports on switch are tagged. I've tested this with a physically attached laptop and right now I'm testing it with a virtual machine (PC) on a Hyper-v server (which I did at my other site to confirm it worked). The VM network port is untagged as it should be.

    Pretty much the Sophos firewall connects the Datto switch, for that uplink port the VLAN is tagged, then I've tagged the port that goes to my Hyper-v server. Also I tagged the port that goes to the Unifi AP as well.

  • I've also now removed the Datto switch from the equation, and put a different switch, a Dell switch at the front. I tagged the trunk/uplink port to the firewall and untagged port 2 as a VLAN access port for VLAN 200, and plugged my laptop in again, and still no IP address from DHCP.