Static IP

RBJ2

Junior Member
Apr 21, 2017
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I notice for some yrs now my home IP has stayed the same but I don't pay nor ask for a static IP. I remember a company where I used to work paid the ISP more for a static address. I guess they stay the same nowdays for most folks but are not garaunteed to do so unless you pay extra ?
 

Gryz

Golden Member
Aug 28, 2010
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Dynamically assigned addresses from public address space only make sense for devices/customers that are temporarily connected to the Internet. In other words: dialup users.

If you have a fiber-connection, a DSL-line or cable, your home-router is connected to the Internet permanently. This means your home-router constantly needs an IP-address. Why give you a temporal one ? It only makes it a lot harder to track which user has which IP-address at a given time. (In most countries, ISPs are obliged by law to keep track). You're not gonna save on IP-addresses, if you give temporal IP-addresses to customers that are permanently connected. So I think a lot of ISPs world-wide just give their residential users a static IP-address.

My ISP even gives us a webpage where we can assign a DNS name to our IP-address. That way you can always do ssh or use http to a fixed domainname, to get to your home-network. Very convenient. Because of this, I remember my home-router's domain-name, not it's IP-address. But I think that my IP-address has been the same now for 15+ years. I'm not paying anything extra.

ISPs that want to charge you extra for a static IP-address are evil muney-grabbing bastards.
Let me guess, your ISP is in the US ?
 
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mxnerd

Diamond Member
Jul 6, 2007
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I believe Charter give residential customer a dynamic IP. But it has a very long lease time, probably several days.

So if your modem is not down for several days, you basically will get a static IP.

My experience is it seems that Charter will rotate customer's IP range from time to time, probably every half year.

I'm in California, but right now if I check my IP through IPchicken.com, my name is like xxx.xxx.xxx.xxx.dhcp.unas.mo.charter.com, that's weird, which should be in Missouri, but if I do tracert test, I'm still in California. But my IP might rotate back to xxx.xxx.xxx.xxx.dhcp.unas.ca.charter.com someday.

Every time when they are rotating the IP ranges, I'll have trouble getting online. It usually happens in weekend though.
 
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VirtualLarry

No Lifer
Aug 25, 2001
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You're not gonna save on IP-addresses, if you give temporal IP-addresses to customers that are permanently connected. So I think a lot of ISPs world-wide just give their residential users a static IP-address.
...and you would be wrong.

You are not accounting for administrative overhead, for assigning and re-numbering static IP, if your IP allocation block for your ISP gets bumped by your number registrar.
 

ch33zw1z

Lifer
Nov 4, 2004
35,271
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...and you would be wrong.

You are not accounting for administrative overhead, for assigning and re-numbering static IP, if your IP allocation block for your ISP gets bumped by your number registrar.
It is less labor intensive to allocate dynamically. My Comcast connection is DHCP, it's rare I cycle my modem, but it still renews the IP like every 3 days or something.

Gryz is correct that some isp's use this as a way to add a cost to static IP allocation, but it's reflective of the labor overhead like you note.
 

Gryz

Golden Member
Aug 28, 2010
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...and you would be wrong.
Not sure what you mean.
Of course there is value in the fact that you keep extra flexibility when you don't promise your customers anything.
But at the same time, if you re-assign ip-addresses often, you need to keep track of the assignment.
Also, ip-addresses are not identifiers. They are locators. You get the ip-address that tells the Internet *where* you are located (topographically). Not *who* you are (identifier). Even inside an ISP's network, ip-addresses have topographical meaning. You can't (or shouldn't) just re-assign ip-addresses just like that.

You are not accounting for administrative overhead, for assigning and re-numbering static IP, if your IP allocation block for your ISP gets bumped by your number registrar.
The administrative overhead is there anyway. But that's somewhere stored in your subscriber-management database. ISPs need to keep track who uses what ip-address anyway.

What does this mean ?
"your IP allocation block for your ISP gets bumped by your number registrar." ?
Address allocations by a registrar to an ISP (or an enterprise) are indefinite. You get the ip-prefix, you kinda own it. A registar will not ask you to give ip-addresses back. (Unless they were ipv4, and you weren't using them for a long period of time). A registar will not suddenly change the prefix you received earlier.
 

Gryz

Golden Member
Aug 28, 2010
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It is less labor intensive to allocate dynamically.
I don't think it matters.

Residential ISPs use a particular type of routers to connect their DSLAMs, their fiber-concentrators, their cell-phone networks, and their CMTSes (cable) to their network. Those routers are called BNG (Broadband (or Border) Network Gateway) or BRAS (Broadband Remote Access Server). An important piece of software on those is called "Subscriber Management". That is software that talks to a large database in the data-center that keeps track of all customers, their ip-addresses, when they are logged in or connected, the network-speed they paid for, the remaining amount of data your can download, etc. Radius and Diameter are protocols to talk to such databases. There can be tens of thousands, up to 100k subscribers connected to a single router. All the management of customers (=subscribers) is automated. It really doesn't make much difference to give customers dynamic or static ip-addresses.
 

Red Squirrel

No Lifer
May 24, 2003
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When I had ADSL I used to practically always have the same IP unless my router remained offline for a very long time which never happens. It was nice since I have a couple things on my web server that are setup so only my IP can access, for extra security.

Now that I'm on fibre their setup is different. DHCP lease is set to like 10 minutes. One little blip in the network connection and I get a new IP. Worse is they don't actually offer static IPs. I would pay for one if I could, but they don't even offer it.

As far as how they are allocated, often times it's by MAC address so you would still set your equipment to DHCP if you had a static. Though sometimes they give you the info (IP, subnet mask, etc) and you enter it yourself. DHCP is probably less error prone though, less chance of a customer making a mistake and mucking up the network. I've seen it... Things get fun if the customer accidentally puts the default gateway IP as their static IP.
 

Ichinisan

Lifer
Oct 9, 2002
28,298
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It's "quasi-static" around here. The IP goes back into the pool of available addresses if your router doesn't renew it before it expires. If the ISP's DNS sees the same MAC ID requesting an IP address, it will try to assign the same one if it's still available.
 

MtnMan

Diamond Member
Jul 27, 2004
7,387
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Yea, that's how DHCP works, it hands out the same IP to a MAC address it knows.

Devices in your home probably get the same IP every time they are booted, from the DHCP server running in your router.

Test it out, change the MAC of your routers WAN side (typically called cloning) and reboot everything and you will be assigned a different IP.
 
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