I have my modem configured for bridge mode. I get one IPv4 for my router and one goes to my server for public access. If I static assigned these IPv4 address would I keep them as long as no one else ended up with them?

How does DHCP work from the ISP side. I assume it is just like any other DHCP server?

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3 Answers 3


Yes: it's normal DHCP as far as you are concerned. They might have different server software with different provisioning tools. You just have to stick to what the DHCP protocol provides you. That includes only using the IP addresses you get for as long as the lease time is and refreshing that lease before it expires.

Just statically configuring an address and not getting/extending the lease with DHCP will not work. It might work if what you configure matches a still active DHCP lease but it will stop working once that lease exires.

  • 2
    To expand on how the address might stop working when the lease expires, ISP equipment is often configured to block traffic from addresses that weren't assigned by DHCP. For example, Cisco's IP Source Guard will block the use of addresses that aren't assigned by DHCP.
    – jda
    Jul 25, 2015 at 22:30

The IP address you are assigned by your ISP may change over time. You should be able to contact your provider and ask for a static IP address. They may charge you more though...


Depending on the type of ISP (COMCAST/others) and business or residential. My IP at home haven't been changed 2 months now. The IP at the office changes every 48 hours (Comcast wanted $$$ =) ).

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