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I enabled gufw with it's default settings, deny incoming, allow outgoing. I haven't noticed any problems with usability, but I was told that I have to allow incoming UDP traffic from port 68. Do I really need DHCP as a normal user? And if so, do I have to allow incoming traffic from port 68 for proper functionality? What would happen if I didn't?

Finally, if I do have to allow incoming UDP traffic from port 68, would I be able to specify it to only allow traffic from say 192.168.1.1? Or would that still effect the functionality?

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    If you are not having any problems, then don't make any changes.
    – user535733
    Commented Dec 30, 2019 at 0:12

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If your IP is dynamically allocated, then you need DHCP. Ports 67 and 68 are used to talk to the Router/Server that assigns the IP address. These addresses have leases that expire. If you aren't communicating on port 67/68 after being assigned an IP, it could be expired early. If it expires early or naturally, you'll lose your internet. Port 67/68 is used to keep track of this, which is important if multiple computers are being assigned addresses.

The default dynamic DHCP address ranges are 192.168.1.100 to 192.168.1.149. Other 192.168.. addresses, on both sides of the dynamic range, could be assigned as static, and if so, you could probably block ports 67/68 after you've been assigned an IP address. Why bother? If you are running a firewall, than that alone will block the minimum abuse that can occur on those ports, so blocking them is pointless. ... Unless you care that a server knows when your computer has its internet connected.

If you control the Router/Server/WIFI hot-spot, you can disable DHCP and use a static IP address.

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  • “The default dynamic DHCP address ranges are 192.168.1.100 to 192.168.1.149.” Where is this specified? AFAIK it depends on the router vendor.
    – Melebius
    Commented Jan 16, 2020 at 13:08

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