Use a static IP address with PPPoE

I've got an access point with OpenWrt which is connected to an ADSL modem in bridge mode. PPPoE is therefore handled by the access point and it works fine. I'd like to know if it's possible to use a static IP address in this configuration. I don't see anything about it in the wiki.

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A static IP address for what? Your access point*, for your internal network? That is the default, and by default it's 192.168.1.1.

*) In this context, this is your router.

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No. For my WAN connection. The PPPoE server seems to hand me an IP address/gateway/mask. I'd like to know if it's possible to use a different IP address/gateway/mask.

The ISP controls what public IP you have and that is the only one you can use.

Some may offer a "static" service where they reserve an IP for you so you always get the same one, but you usually have to pay extra for that.

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I know that there is nothing that technically stops me from trying to use another IP address (which doesn't mean I will get connectivity to the Internet) and I would like to do that.

Why would you do that? At best it won't work, and at worst you could disrupt someone else's service.

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PPPoE is not designed for the client to set an IP of its own choosing, like it is possible with DHCP, and the IP is always provided by the upstream PPP server - that is the way client and server interact over PPP.

In the relationship with the ISP your node can only be the client.

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Thanks for your thoughtful answers.

If someone can please assist me with the question I asked, I'm all ears.

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Does it mean PPPoE uses modified PPP, since PPP allows the sender of the Configure-Request to state which IP-address is desired?

  This Configuration Option provides a way to negotiate the IP
  address to be used on the local end of the link.  It allows the
  sender of the Configure-Request to state which IP-address is
  desired, or to request that the peer provide the information.  The
  peer can provide this information by NAKing the option, and
  returning a valid IP-address.

https://tools.ietf.org/html/rfc1332#section-3

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The PPP stack is being leveraged but PPPoE transforms the P2P nature into a S2C relationship since multiple hosts can connect to a point of service over a single physical connection.

PPPoE is used foremost as authentication mechanism with the the ISP's DSLAM -> ATM that hosts the Access Concentrator.

LCP forms part of the PPP stack and provides the protocol wrapper for:

  • authentication
  • compression
  • sanitisation

Secondly NCP | IPCP as part of the PPP stack configure the client's IPv4 address and DNS servers.

No, at worst one can be arrested and prosecuted and/or sued. This is a crime in the US and other jurisdictions.

So, most likely, the OP's asking us to provide technical details that violate the Community Guidelines.

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That sounds like inferring some sort of a veiled malicious intent whilst the use case is not explicitly stated by the OP. Whatever the use case it might be entirely begin, same as it could be malicious.

Supposedly

has been responded to fair and square. Whether that will prevent the OP from trying to do otherwise

is perhaps the OP's sole prerogative and inherent risk - depending on the judiciary and ToS applicable for the OP.

The guidelines stating

You may not post descriptions of, links to, or methods for stealing someone’s intellectual property (software, video, audio, images), or for breaking any other law.

Nobody participating in this thread has attempted such thing. It is not even clear whether trying to set a static IP from the PPPoE client side would account as such.

I didn't intend to reply again until someone actually answered my question, but really, suggesting that I'm just trying to DoS someone's connection? If you can't answer my question please ignore it altogether instead of calling me a criminal.

Nobody did so. All there has been a consideration of a potential violation of forum community guidelines, whether warranted is a different matter.

Nobody suggested as such either


Your question has been answered but apparently not to your liking. Insisting that it has to be feasible does not make it come true.

Some years back some router distros indeed provided such feature which led to potential IP hijacking a/o DoS attacks on the ISP's Access Concentrator.

The PPPoE client code implementation in OpenWrt does not provide such option however. If you do not trust that you may peruse the OpenWrt source code.


Unfortunately you did not state whether you want to assign a publicly routable IP or a private one, which makes a difference, as it is not clear what you want to achieve.

Unless you purchased a publicly routable IP (block) any such IP is the property of its proprietor and latter's prerogative to utilise whichever way, as in leasing it to a (subscriber) peer and not for the peer to attempt otherwise.

If instead you want the WAN interface however to be reachable via a private IP that can be done via

ip a a <ip address/prefix> dev pppoe-wan


Is entirely unrelated to PPPoE anyway but being advertised/broadcasted by the ISP in their WAN-side routing announcement. You may manipulate the routing table with userland, e.g. iproute2

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There is "PPP unnumbered" support anyway.

The borrowed IP address will be shared as local IP address by the PPP daemon and no other local IP will be accepted from the peer in the IPCP negotiation

So it is technically possible. But I already knew that. Indeed years ago I had an ADSL router (I don't remember which, but it had the vanilla ISP firmware, nothing fancy) which allowed me to set a static IP address for my PPPoE connection.

I trust you! But I didn't get this answer at first. Just that I didn't know what I was talking about, or that I could be trying to DoS or that I would end up DoSing someone. I don't believe the wording of my posts warranted such answers.

I was wondering about this, since ip addr seems to show what looks like a gateway, in this case the gateway of my ISP's CG-NAT server:

21: pppoe-wan: <POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP> mtu 1492 qdisc hfsc state UNKNOWN group default qlen 3
    link/ppp
    inet 100.66.163.26 peer 100.66.0.1/32 scope global pppoe-wan
       valid_lft forever preferred_lft forever

The route command does indeed show 100.66.0.1 to be the default gateway.

Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
default         100.66.0.1      0.0.0.0         UG    0      0        0 pppoe-wan
100.66.0.1      *               255.255.255.255 UH    0      0        0 pppoe-wan
192.168.1.0     *               255.255.255.0   U     0      0        0 eth1
192.168.255.0   *               255.255.255.0   U     0      0        0 br-lan

I assume I could just alter those IP addresses (IP and gateway) using ip commands, since OpenWrt does not have builtin options to do so?

Thank you for your time.

Partially correct. Mainly, you don't have to have malicious intent to violate a ToS by controlling/using an unpurchased IP. It comes from experience that most people:

  • are not familiar with communications as it relates to the border relationship with our carrier
    • of those, a super majority are not aware Laws and Regulations exist about things like this

I respectfully disagree:


you may connect multiple computers/devices within a single home to your modem and/or router to access the Service through a single Verizon-issued IP address

~ Verizon ToS

You may not configure the Service or any related equipment to access or use a static IP address or use any protocol other than DHCP unless you are subject to a Service plan that expressly permits you to do so.

~ Comcast ToS

Almost all ToS'es I've seen state that one cannot use more service, or a method of service different than: purchased/authorized/assigned/provisioned/allocated; or in a manner that can disrupt other users or the carrier, or another carrier/their users. YMMV. And depending on country, it may be the relevant postal or telephone laws applying instead!

So, to be clear, all the OP needs to do is inform us in further chat (he can also ignore, their choice):

  • they live somewhere it's allowed; or
  • connected to an ISP where it's allowed.

Given the connection is PPPoE, that is highly unlikely. BTW, no one has stopped the OP from responding, kind sir. I only noted @mk24's consequences aren't the worst that could happen to most people who may read this thread.

:+1:

Agreed...but it's our responsibility to follow the Guidelines as individuals; I can only suggest someone else does so. The same with the [possibly applicable] law.

:open_mouth:

As many people have commented already, using a static IP is generally a bad idea (be it technical, legal, or just ethical in that it could mess up someone else’s connection).

That said, why do you want a static ip? If it is for setting up a server/service, would a dynamic dns solution work for your needs? As long as you have a publicly routable IP address and assuming such services do not violate your isp’s TOS, this would be an easy option.

If you actually need a static ip for any other reason, reach out to your isp to find out what they can offer and how they would implement it.

(post withdrawn by author, will be automatically deleted in 24 hours unless flagged)

Stop trolling.

I'll quote you:

I partially agree; and realize why I believe your post was off the one topic. I'll be flagging it.

Not sure where your issue with me is stemming from, but let's stick to the static IP on a carrier's PPPoE thing. If you disagree it's wrong, ignore me and help him. I want to know before I assist.