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The question is simple. I have multiple DSL connections. Suppose that I have a server with a single network card. Would be any problems to use a LAN switch to connect DSL modems to the server? How does server associate ISP user/passwords with the proper DSL line? Is this setup safe and stable?

Thank you.

user2798081
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Generally speaking, that kind of setup might work, depending on PPPoE client and server implementation.

When client wants to connect to DSL access concentrator, it first sends PPPoE Active Discovery Initiation broadcast packet, which in case you have multiple DSL modems connected to LAN (L2) switch will reach all your service providers. The packet contains required server/service name, and although it will reach all connected concentrators, they can decide (based on packet data) if they will respond with PPPoE Active Discovery Offer packet, which in return contains server information (MAC address, concentrator/service name).

Once the client has recived offer(s), if the PPPoE client implementation supports it, it could pick only the exact one it intended to contact in the first place and continue with the rest of the stages, communicating only with the one concentarator (based on receives MAC address).

Dusan Bajic
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  • Thanks. Actually, I set this up with two connections of independent service providers and it did worked. I just want to make sure that if I can rely on this configuration with more DSL lines in a production environment. – user2798081 Oct 18 '15 at 07:35
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    Nevertheless, I recommend to use L2 switch supporting 802.1q VLANs and putting each PPPoE carrier into a dedicated VLAN. This is a standard technique of using such swtich to "multiply ports" on the router, called "router-on-a-stick". – Nikita Kipriyanov Sep 26 '21 at 19:32