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Is it possible to use PPP (pppd) to create a network bridge between two subnets? That is, connect two segments of the same network, tunneling Ethernet frames, rather than IP packets?

As I understand, PPP is basically a fancy mechanism for sending data packets/frames over a serial line, so it seems it should be possible to use it for any kind of packets/frames.

To expand my question: I have a standard, home, local network which has a subnet like 192.168.1.0/24 with a router that runs a DHCP server. I'd like to connect another machine via PPP to this network so that it becomes a part of the subnet, for example:

  • It can request and get a DHCP address from the server.
  • It can access .local addresses in the network.

For this I'd like to create a network bridge using PPP over a serial line between this machine and another machine that is already in the network. I know how to create a bridge between interfaces in these machines, but not how to set up PPP to transfer Ethernet frames between them, if that's possible.

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  • Any reason why PPP? You can definitely do this with a VPN and L2TP. Are you using something other than IP?
    – Appleoddity
    Oct 16, 2017 at 2:06
  • @Appleoddity It doesn't have to be PPP, and I'm using IP. But I'd like to understand various options, both theoretical and practical, to get better comprehension of how networking works in detail. VPN seems to be too high level. I'll look into L2TP, thanks for the pointer.
    – Petr
    Oct 16, 2017 at 6:54
  • Understandably then, your request isn't super clear on what your end goal is. It's hard to give you precise answers when you don't have a specific topology and end goal in mind. This type of question isn't well suited to the question/answer format here. L2TP is VPN technology.
    – Appleoddity
    Oct 16, 2017 at 14:48
  • @Appleoddity I understand, and I extended my question with more precise description of my goal. I hope it's better now, if not, I'll appreciate any further pointers how to improve it.
    – Petr
    Oct 16, 2017 at 19:21
  • It is much better. But, just because I don't like to assume things - where is the computer you want to connect to your network located? Is it out on the internet somewhere? It does sound like you are describing a VPN scenario. One technology of which is PPTP, which might be what you are asking about? The last time I used PPP to connect a computer to another network like you describe I was using a 56k baud modem on Win 3.1.
    – Appleoddity
    Oct 16, 2017 at 19:27

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connect two segments of the same network, tunneling Ethernet frames, rather than IP packets?

I do not believe so, at least not directly(without a VPN or other additional encapsulation).

As I understand, PPP is basically a fancy mechanism for sending data packets/frames over a serial line.

Yes, but largely OSI layer 3 packet types that would normally go a layer above OSI layer 2(like Ethernet) frames, not raw Ethernet frames directly. There are corresponding PPP protocol numbers IP/IPX/IPv6/..., but not Ethernet.

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