Internal DHCP issue when WAN1 has gone down.

[SimonWW]

Hi I am new to this forum.

I have seen issues whereby I have a DHCP server running on an internal interface that functions as expected and feeding IP addresses to internal clients. The problem is that if you lose internet connectivity via WAN1 for instance, you will have issues with clients trying to get DHCP off the internal interface / DHCP server binding to that internal  interface. 

I did a "diag debug app dhcps -1" and I can see incoming requests to the FG60d in my case with the firewall seemingly giving out DHCP addresses. Also any client reservations appear to get issued off the firewall OK yet the client PC / Phone etc will not get the IP allocation. 

This manifests itself on all types of client. I am part wondering if it has something to do with the microsoft NCSI connectivity check deciding  that if it can't get to the internet it will not keep the DHCP client address. Same happens with android clients.

I would have expected the client to keep the allocation even though there is no internet upstream connectivity.

I have seen this on other FG series firewalls and only manifests itself when upstream internet connectivity is lost.

Anyone seen this behavior? Really annoying when you can't manage you own firewall via a DHCP client. I have to assign a static IP to manage the firewall.

Thanks,

Simon