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Windol
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DHCP Issues on Port 4 Despite Normal EoIP Operation

Wed Apr 09, 2025 6:07 am

Hello,

I’m encountering a problem with my current MikroTik router configuration. I have two routers connected to a cloud server via a Wireguard VPN. Both routers also have an EoIP tunnel configured. Here is my setup:
  • Client Router:
    • Connected to the cloud server through Wireguard.
    • An EoIP interface is configured and added to a bridge that runs the DHCP server (for instance, managing the 192.168.1.0/24 network).
  • Central Router:
    • Also connected to the cloud server via Wireguard.
    • Has an EoIP tunnel configured to connect with the client router’s EoIP interface.
    • The EoIP interface is added to a bridge along with physical port 4.
    • The objective is for any device that connects to port 4 to receive an IP address from the DHCP server located on the client router.
Issue:
While the EoIP tunnel establishes and operates normally, devices connected to port 4 on the central router are not obtaining an IP address. I have verified that both the Wireguard VPN and the EoIP tunnel are functioning as expected, leading me to suspect that DHCP broadcast traffic might not be properly traversing the EoIP tunnel, or that there is another configuration issue (possibly related to firewall or NAT settings) interfering with DHCP requests.

Additional Details:
  • RouterOS version in use: 7.17.2
  • The EoIP tunnel is configured with an appropriate MTU adjustment (around 1400) to accommodate encapsulation overhead.
Could anyone provide guidance, troubleshooting tips, or potential configuration adjustments to resolve this issue? Any help to ensure that DHCP broadcast packets successfully pass through the EoIP tunnel to the client router’s DHCP server would be greatly appreciated.

Thank you in advance.
 
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anav
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Re: DHCP Issues on Port 4 Despite Normal EoIP Operation

Wed Apr 09, 2025 11:28 pm

Can you post your latest config on both routers.
/export file=anynameyouwish ( minus router serial number, any public WANIP info, keys. )
 
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sindy
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Re: DHCP Issues on Port 4 Despite Normal EoIP Operation

Wed Apr 09, 2025 11:35 pm

Is the central router a physical one or is it a virtual one running on some virtualisation platform? A common behavior of virtualisation platforms is that they block traffic to/from MAC addresses other than the one of the virtual NIC, so the virtual machine cannot act as a bridge. This is considered a security feature and can be changed in most cases. But if that was the case, it should block all traffic that would otherwise pass through the EoIP, not just the DHCP one.