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I'm having trouble wrapping my head around how LAN to WAN and vice versa works. To give an example that might be helpful. On a given network, you use a domain's WAN to remote into their term server from which point you can access the rest of the network devices on that domain. I understand this conceptually to some degree, but I'd appreciate some further insight on this. A visual illustration of how this works, would be helpful. Thanks.

xpkiro
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    I think the context you are providing is too complicated for developing an initial understanding and feeling of comfort. Just start with this thought. On the Internet, every network is connected, so from any one networks perspective, The LAN is always that network, and the WAN is always **Everywhere** else. LAN and WAN are just like "Left" and "Right". understanding them requires an understanding of who the directions are in relation to, and what direction they are facing at that second. – Frank Thomas Sep 16 '15 at 16:53
  • Judging by your use of the terminology, I'd say you are lacking some fundamental understandings oyu should know before trying to figure out how they interact. Start with these to get a grasp on what a LAN and WAN are defined as: LAN: https://en.wikipedia.org/wiki/Local_area_network, WAN: https://en.wikipedia.org/wiki/Wide_area_network – Ƭᴇcʜιᴇ007 Sep 16 '15 at 16:55
  • When speaking of home routers, there is a definite LAN and definite WAN interface, but that comes from a bunch of assumptions about how the device is used, for what purpose, etc. For instance, your home routers WAN port is connected to the ISPs LAN. but the ISP has a WAN as well, and so does every upstream provider they utilize. – Frank Thomas Sep 16 '15 at 16:55
  • Related SU question/answers: [What is the real difference between LAN and WAN?](http://superuser.com/questions/326939/what-is-the-real-difference-between-lan-and-wan) – Ƭᴇcʜιᴇ007 Sep 16 '15 at 16:56
  • Thanks to all for the feedback. I am getting a better grasp on how lan to wan works. An example of something that confused me at a site I worked on is as follows - The company used a company for their ISP (we'll call them Xomcast) and from Xomcast's router an ethernet cable went into another router (we'll call it Tonicwall). The ethernet port was plugged into the wan port on the Tonicwall. This provided the connectivity of their other network devices. I don't understand how LAN to WAN works in this situation. I would think the devices are all on a LAN and should be going to a WAN? – xpkiro Sep 16 '15 at 17:07
  • Sorry if that's confusing. – xpkiro Sep 16 '15 at 17:12
  • You're confused because the routers/firewalls in question erroneously mark/refer to a certain port as "WAN", when that port doesn't have to be a 'WAN' at all. WAN and LAN are concepts that depend on context. In reality there's no real difference between routing traffic travelling "LAN to WAN" and "LAN to another LAN". Similar to Uploading vs. Downloading, where it's the exact same thing happening, but what you call it depends on which end your on, and which way the data is being transferred. – Ƭᴇcʜιᴇ007 Sep 16 '15 at 17:38
  • In the old days, the Telco's would reffer to to point at which the telco's hardware stopped, and the customers hardware started the `demarc`. Essentially, they were responsible for everything outside the demarc, and the customer was responible for everything inside it. The way you are using the term WAN is essentially the same way they used demarc, and that usage is quite common these days, but its always from the context of a specific LAN. – Frank Thomas Sep 16 '15 at 20:20

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Imagine that you live in your own house in some small remote village. Your front door is a router. Your own rooms are on the inside (the "LAN" side), and the rest of the world is outside (the "WAN" side). Now think about your driveway. You can again go two ways – towards your home ("LAN") or drive out towards the rest of the world ("WAN"). The town itself has one, maybe two roads going "outside". (However, once you get to the larger cities, they're all interconnected somehow, with many routes in various directions, and there is no single "WAN" path anymore.)

It's a poor analogy, but maybe it'll get the point across – the internet actually seems quite similar to me: There isn't necessarily a clear line between "belonging to LAN" and "belonging to WAN". The router merely shuffles packets between arbitrary interfaces.

Instead, in this situation, "LAN" and "WAN" are just names describing the port function. You're at the "end" of a connection, and your routers are configured for the typical asymmetric routing, where one interface receives a connection from the "outside", and that connection is provided to the LAN.

Often the "WAN" interface also runs a DHCP client to obtain its own IP address from the ISP, while the "LAN" interfaces run a DHCP server to provide IP addresses to connected devices.

(In contrast, a core/backbone router would have a more-or-less symmetric configuration, with many routes through all interfaces – not receiving/providing a connection, but joining parts of the internet together.)

u1686_grawity
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