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I've been working with LANs using Ubuntu for some time now. So I have 2 office locations, each with their own Ubuntu servers. Now we need to link them and we have been provided with a leased line. In summary,

  • Each server works fine within their LAN
  • Each network has its own Internet connection (not relevant I think)
  • Each LAN can ping the remote router. i.e., Office A allows to ping router A and vice versa.

But I cannot go beyond the router in the remote office. For example, from offcie A, I can ping the router of office B but NOT the server of that office.

Am I missing something? Please advise what needs to be done.

Each machine has a static IP.

Thanks! enter image description here

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  • Do you have NAT properly configured on both of your "DSL leased line routers"? This is important to ensure that the ip addresses in one site are visible to all of the machines at the other site.
    – MGodby
    Sep 8, 2014 at 11:58
  • Do the routers create a (transparent) VPN?
    – Jan
    Sep 8, 2014 at 12:05
  • @MGodby How would I know if NAT is properly configured? Does it mean anything if I can ping each router from the remote location?
    – itsols
    Sep 8, 2014 at 12:07
  • @Jan I'm a little lost about this. What is a transparent VPN and how do I find out if I have it?
    – itsols
    Sep 8, 2014 at 12:08
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    i.e., your DSL leased line routers need to advertise to each other any ip addresses behind them that you would need to reach from the other site. By default, the line routers are probably only presenting their own primary ip addresses to each other.
    – MGodby
    Sep 8, 2014 at 12:24

2 Answers 2

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The router needs to know to which server it has to forward requests to. You now have one server in each location, but that doesn't matter for the router. So you need to configure port forwarding. In the router you can set which port has to be forwarded to which machine or IP address. That machine has to accept that traffic, so you may need to configure the firewall of the server.

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  • I'm quite ignorant when it comes to WANs. I haven't touched anything on the routers as they've been given to us 'all-configured' (I presume) by the phone company. Since I can ping the remote router doesn't it mean that things are supposed to be in order?
    – itsols
    Sep 8, 2014 at 12:13
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    You ping the router, which you can consider as a computer in itself. That you can ping only lets you know that the router is responding to ping, nothing more. The router is dumb. It only knows what you tell it to do. You need to tell it to route the specific traffic to the server.
    – SPRBRN
    Sep 8, 2014 at 13:28
  • Yup, that makes sense. Let me check out the routers. Thanks!
    – itsols
    Sep 8, 2014 at 13:53
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There are many possibilities how you could set this up, none of which are trivial. Among others, you could

  • setup a site-to-site VPN
  • setup NAT

VPNs have the advantage of providing encrypted communication channels, which is highly recommended these days. They are somewhat difficult to setup for a rookie, but once in place, they work transparently.

NAT is a bit easier to configure, but wouldn't secure the communication (ie. if the protocol is unencrypted then the network data may be read by the telcos).

In any case, you need to know

  • about networking
  • how to operate the routers given to you by the telco
  • the link is going to be used (VoIP, HTTP, SMB, ...?)
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  • Thank you for your answer. If I were to use the NAT path towards implementing this, what steps would I need to follow? Do you have a tutorial link for this?
    – itsols
    Sep 8, 2014 at 12:48
  • BTW, I'm keen on two things. One is that each server should be able to access the other's Postgres DB. I know how to configure that part but not the part of getting each server to communicate - at least respond to a ping. The second objective is that I want to run a client program on one network so that the other server's DB is used. Again, I'll work using the IPs for connection.
    – itsols
    Sep 8, 2014 at 12:50
  • Once you have a VPN ready, the offices communicate transparently. My advice: Get help of a network professional
    – Jan
    Sep 8, 2014 at 12:55

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