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Short bg:

I wanted to host a website on my laptop (192.168.0.102) via apache server. I set up port 8080 and forwarded the port that I was able to access it via 192.168.0.102:8080. Then there was a problem that via my public IP (91.223.224.42) I could not do so. My router has a WAN of 192.168.13.234 (and, btw, I was also able to access the website via 192.168.13.234:8080) and is standing behind a router with an IP of 192.168.30.105. So I called my ISP and they told me, that the last router is their PPPOE router, and so that I will only be able to access my laptop from the outside if I pay for static IP address, because "my current public IP corresponds to PPPOE server and I need the static routing".*

I googled and found out that there are routable and non routable IP addresses, but did not find any explanation relating to my problem, only found definitions of local subnets as 192.168... and public IP, but I already know that. I think I also get what dynamic IP and static IP mean but I am not familiar with PPPOE and why is that so important to get static IP if I am dealing with PPOE.

Thanks in advance!

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  • What is your router model? This doesn't sound like a business Internet connection.
    – Ron Maupin ♦
    Apr 10, 2017 at 11:44
  • it's a tplink something. Just your usual not too expensive router with 2 antennas for wifi
    – user35914
    Apr 11, 2017 at 8:35
  • Unfortunately, questions about home networking and consumer-grade devices are explicitly off-topic here, as are questions about networks you do not control, e.g. your ISP. You can ask about those on Super User, where you should search for CGN, which it appears your ISP is doing. Residential ISPs have a clause in your agreement that prevents you from running servers on your network, so they don't care that CGN prevents that.
    – Ron Maupin ♦
    Apr 11, 2017 at 13:16

4 Answers 4

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What is a “routable” IP?

IP addresses can be divided into several categories.

  • Routable on the public Internet.
  • Routable on private networks but not on the public Internet
  • Not routable at all.

People often say "routable" when they mean "publically routable" and "non-routable" when they mean "not publically routable"

The IANA maintains a list of special purpose IP addresses at https://www.iana.org/assignments/iana-ipv4-special-registry/iana-ipv4-special-registry.xhtml the "forwardable" column tells you whether the addresses can be routed on private networks, the "Globally Reachable" column tells you whether the addresses can be routed on the public Internet.

If it's not on that list then it's most likely a regular publically routable IP.

Note that publically routable doesn't necessarily mean publically routed. Some ISPs (cellular providers in particular) have been known to abuse space that was either unallocated or allocated to companies who chose not to advertise it on the public Internet to give them additional space for addressing devices behind their NATs. This causes problems when the legitimate owners of the IP space later decide to start using it on the public internet.

Probablly the best test is to do what you just did, compare the "WAN" IP address shown by your NAT router to the address shown by a "what is my IP" site.

I think I also get what dynamic IP and static IP mean but I am not familiar with PPPOE and why is that so important to get static IP if I am dealing with PPOE.

PPPOE has little to do with it beyond the fact that the "PPPoE server" is likely the first IP device your traffic hits in your ISPs network.

NAT can be used to translate the addresses on packets to hide multiple clients behind one address. In your case you have two layers of NAT, your local "router" acts as a NAT hiding your private network behind 192.168.13.234 your ISP in turn has a NAT hiding multiple customers behind 91.223.224.42.

If you control the NAT you can "port forward" incoming services through it, but if you don't control the NAT you can't do that. So you can forward stuff through your NAT but it doesn't really help you because you can't forward it through the ISPs NAT to your NAT.

I will only be able to access my laptop from the outside if I pay for static IP address, because "my current public IP corresponds to PPPOE server and I need the static routing".

That is more of a policy thing than a technical thing. Your ISP could offer a "dynamic public IP" option but they have chosen not to. So your choices are a dynamic private IP behind a NAT or a static public IP.

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  • That really clears everything out. Thank You very much, sir :)
    – user35914
    Apr 11, 2017 at 10:11
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All IP addresses are routable, the Internet Protocol was designed for this very purpose.

But not all of them are routed everywhere

There's a bunch of network that were assigned for specific purposes and that are not routed on the public Internet

The 2 most common type of IP addresses you will heard off are commonly called public IP addresses and private IP addresses

  • a public IP address is a "normal" IP address which has not been assigned for special purpose. Those addresses are routable on the public Internet.

  • a private IP address is defined by rfc1918

Those addresses are :

 10.0.0.0        -   10.255.255.255  (10/8 prefix)
 172.16.0.0      -   172.31.255.255  (172.16/12 prefix)
 192.168.0.0     -   192.168.255.255 (192.168/16 prefix)

Anyone can use those addresses in private network, but due to this, those addresses are no longer unique and so cannot be routed on the Internet. Any decent Internet Service Provider will drop packets that have such address as source or destination.
But in private LAN, those addresses are routed, within the company network or even between different companies that have (private) cross connectivity.

There's other type of reserved addresses that are not public nor private, for example loopback addresses , 127.0.0.0/8 cannot be routed at all, even on private networks, or multicast addresses, 224.0.0.0/4 which, in theory, could be routed on the Internet, but practically is not routed, since it was not really designed for a worldwide internet.

You will find all reserved IP addresses on the Wikipedia page Reserved IP addresses, or as pointed out by RonMaupin you'll find a more technical but more accurate and with appropriate official reference source at the IANA IPv4 Special-Purpose Address Registry page

Concerning static IP and PPoE, those are 2 different things.
PPPoE is widely found in ADSL connection (but not only); ADSL specifically is a bad fit to host services (which is why you need a fixed IP) because the "A" stand for "Asymmetric". I.E. the upload speed is much lower than the download speed.

So it's uncommon to have fixed IP on an ADSL / PPPoE connection but it's perfectly possible (if your ISP is willing to provide it).

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  • 2
    I like the IANA IPv4 Special-Purpose Address Registry that describes the different ranges, including if a range is global or routable.
    – Ron Maupin ♦
    Apr 10, 2017 at 15:11
  • Thanks, that also helps. Didn't know about this ADSL feature :)
    – user35914
    Apr 11, 2017 at 10:15
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192.168.0.0 this is a private range , that means traffic coming from this IP

range will not be routed to the internet. It's reserved to the private network

use , along with (172.16.0.0) and (10.0.0.0) ranges . so when you see those ranges you

should know you are in a private network.

Dynamic IP changes every time you router rebooted . So people can't access your

website . what You need is an static IP , which will remain the same .

Static IP comes with extra charge , you can discuss the cost with your

ISP presenter .

Finally , there is a lot of free or paid hosting Services you can use to host

your website .

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  • I'm sorry, perhaps, I didn't express myself correct enough. I know all of that. I also know, that, I should be able to access to my PC via Public IP and it doesn't matter if it's dynamic or static. I know that dynamic changes and I have to keep track of that. But still, I should be able to access it. So I do not understand how static number would change anything related to the network settings, it would only bring more convenience that I wouldn't have to keep track of constantly changing IP.
    – user35914
    Apr 11, 2017 at 8:42
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It is a basic concept. The IP that ISP provided may have been 'Shared' among different clients. As ISP advised, you need to buy/rend a static IP from ISP. Routeable IPs are public IPs on the internet. You need to NAT your private IP to public IP so the website can be reachable from the internet. As for now, you only seem to access on intranet i.e locally defined private IP.

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  • Wow, if ISP really uses one public IP for several clients and I am just one of them, then it all makes sense! That's a brilliant answer, thanks.
    – user35914
    Apr 11, 2017 at 8:44
  • Yes. By shared, I meant local users on private subnet are natting (PAT mostly) towards ISP IP and they are connecting from single IP with different ports. Port size is defined by 16 bits.
    – Muneeb Ali
    Apr 13, 2017 at 8:14
  • ISP use different architecture allowing tenants or subscribers to user public internet which may result in complexities. The concept is simple to solve your issue. I hope you resolve your issue.
    – Muneeb Ali
    Apr 13, 2017 at 8:16