Dynamic IP vs Static IP rates
Why/How are dynamic IPs cheaper than static IPs?
Tried googling about this but all I got are definitions of what dynamic/static IPs are but economically, why though?
For residential connections, wouldn't it be cheaper to just allocate an address and be done with (until the user cancels their subscription or something) rather than dealing with the whole IP pools & recycling addresses shenanigans?
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I live in a tourist area where there is a big difference in users during different times of year and so using dynamic IPs with varying lease times makes sense. During the time when there are fewer users the IP leases are very long and I can keep the same IP for a month or more, but in times of many users the IP leases can be as short as a day or less. This allows the local telecom to make the best use of their IP space.
I'm talking about dsl lines into houses and condos, that are not occupied in a lot of cases for half the year.
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In the dial-up broadband days, you didn't really need a constant internet connection, so IPs would be temporarily assigned and rotated throughout the customer base as needed. So some of the reasoning is historical.
Less overhead needed if you just temporarily assign IPs to customers as needed rather than explicitly linking them to customers 1-to-1.
Gotta sell those sweet perks somehow too! "Only pay $XXX/mo for your PREMIUM, BUSINESS-ready Static IP Address!"
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@Mason Wouldn't it be the other way around though? Give them an IP and just forget about it
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How is rotating customers' IP making the best use of one's IP space though?
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Let' say you have 1000 customers paying a land line phone bill that includes a dsl connection, but only 500 of them are connected at any one time, or for half the year they are not even in their vacation homes. Why would you want to tie up a 1000 IPs, 500 of which are not being used at all ?
A second factor is the telecom covers the whole country, so when it is low season here it is high season in other locations and vise versa so they can move IP blocks around to where they are needed creating smaller or larger pools depending on local demand at that time of year.
If you are seeing it as if 1000 customers are always connected and using their connections why would using dynamic IP leases make sense?
In that case it would not, but that is not how the customer base in my area uses their dsl lines.
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The dynamic IP address for our home never changes. It survives power outages of longer than half a day, and survives separate reboots of the modem and firewall. I am not a conspiracy theorist, but I felt that it had to be giving the ISP some kind of tracking advantage that translates into financial reward. They made it nearly impossible for the average user to change their IP address.
Helpful Hint to Forcibly Change a "Stuck" Home Dynamic IP Address:
To get a new IP address from the ISP's DHCP server, change the MAC address for the WAN port on the firewall/router. Reboot your network devices (modem, firewall/router, etc.) to trigger the change. I discovered that nifty solution while looking at the DHCP side of the problem.
It makes no difference for ISP if they will lookup via IP, MAC, PPPoE login or whatever you use there. You are a conspiracy theorist here ;-)
Maybe they are not running dynamic IPs anymore, maybe you are offline too short (what is your lease time?), maybe your network is grandfathered from some older ISP/network and they have it static in that part. Some run dynamic, some run static, some run both.
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https://lowendspirit.com/uploads/editor/gi/ippw0lcmqowk.png
I will accept the "conspiracy theorist" title for this instance. Let me say that having a consistent IP address that does not change over a period of months (or years) makes it easier for third-party tracking, too. It may not be only related to the local ISP, if you want to "expand the conspiracy." Others have suggested that it is just the way that the ISP's DHCP server operates. I never tried to fingerprint it.
It is definitely a dynamic IP address. The service is sold that way. My firewall/router must go to their DHCP server to get a public IP address. The point is that the ISP's DHCP server always returns the same public IP address for my equipment. Since most customers' equipment rarely changes, they get one IP address that does not change.
As I said above, if you change the MAC address of the WAN port and force a new DHCP request (through rebooting or the firewall's user interface), you will get a completely different IP address. The new IP address will not change as long as you keep using the same new MAC address on the WAN port. As far as I can tell, the IP address is matched to the WAN port's MAC address in some way.
One test that I have not run is where I use one MAC address (1st IP address), change the MAC address to get a new IP address (2nd), use it for a several months, and then change the MAC address back to the original (3rd IP address).
-> My hypothesis is that the 3rd IP address will NOT match the 1st IP address. I believe that if enough time has passed, the original IP address will be reassigned to someone else. I do not have the patience to keep testing to see what that time interval might be.
What I know is that the association between a given MAC address and a recently assigned IP address seems to last a day or more.
For a true static IP address, you must sign up for the much more expensive Business plan.
And that is exactly how dhcp works, and has done for about 30 years.
https://www.rfc-editor.org/rfc/rfc2131
Fair enough. It has been a very long time since I looked at the DHCP RFC. I just pulled the Stevens book off the shelf. It is too old, so it barely mention DHCP (and refers to RFC 1541, now obsolete).
-> Can you point me to a specific paragraph in RFC 2131, to save time?
I can confirm that two ISPs I have behave differently with regards to addressing:
Comcast has around 1-2 hour leases for your IPv4 address provided you do not change your MAC address. This is normal and is how DHCP leases work based on RFC2131.
CenturyLink uses PPPOE so every time it disconnects and reauthenticates I am given a new IPv4 address, because that's typical behavior for PPPOE.
It's all up to the ISP and how their infrastructure is configured and what IP addressing/authentication mechanism they use.
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What exactly are you looking for? You described how a dhcp works pretty accurately in the post above, so I do not really understand what your question is?
I am not ignoring you. Give me a chance to read the RFC carefully, and I will give you a better response. Be patient.
I still think dynamic ip rotation for residential connections is just a money-making scheme tbh....
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The reason for dynamic ip assignment being the most common is probably just because it is the easiest way to do it.
Setup a dhcp infrastructure and everything "just works". Minimal management, you can update or change things like routing, dns servers and gateways and it just propagates by itself to every connected device.
If you had static assignment and still used dhcp, you would loose thousands of ip's every year just because people buy a new router or computer.
If you had static assignment and did not use dhcp, support would be a nightmare. Just imagine the number of calls to the helpdesk from users wondering why their computer cant get online when they plug it in.
And, as many have pointed out, as long as you keep your router or pc connected your ip is most likely more or less static. Most networks run leasetimes at several days, so as long as you stay online you will not get a new ip.
@rcy026 is 100% correct. I started reading RFC 2131 this morning. It did not take long to find the paragraphs that confirm rcy026's assertion. Here are the relevant paragraphs from page 7 of RFC 2131:
"The following list gives design goals specific to the transmission of
the network layer parameters. DHCP must:
o Guarantee that any specific network address will not be in
use by more than one DHCP client at a time,
-> o Retain DHCP client configuration across DHCP client reboot. A
DHCP client should, whenever possible, be assigned the same
configuration parameters (e.g., network address) in response
to each request,
-> o Retain DHCP client configuration across server reboots, and,
whenever possible, a DHCP client should be assigned the same
configuration parameters despite restarts of the DHCP mechanism,
[...]
(Bold emphasis is mine.) Well, that pretty much says it all. You learn something new every day. Thanks to rcy026 for making it plain and clear.
As I said, this is exactly how dhcp works and always has. Everyone with some experience in the field has probably experienced a corrupt dhcp database and know exactly what a pita it is, and how easy it would be to just throw the database away and assign everyone a new address.