Oleksiy Kovyrin

If you have your own home network with two or more computers, you definitely know all of the problems with concurrent access to internet channel. Most annoying problem is bandwidth sharing: when you are trying to use remote ssh connection to some server, and at the same time your wife/brother/friend decided to watch some new and very cool video clip at Google Video or YouTube, your connection will be stalled and you can forget about comfortable work. In this small article I will give you a simple solution for this problem and you will be able to do anything without worrying about traffic sharing problems!

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Sometimes we need to connect two or more geographically distrubuted ethernet networks to one broadcast domain. There can be two different office networks of some company which uses smb protocol partially based on broadcast network messages. Another example of such situation is computer cafes: a couple of computer cafes can provide to users more convinient environment forr playing multiplayer computer games without dedicated servers.

Both sample networks in this article need to have one *nix server for bridging. Our networks can be connected by any possible hardware that provides IP connection between them.

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Some years ago I decided to stop using public mail services and decided to buy my own domain and to setup my own mail server at home to handle all of my email. Work was completed very quickly and I got my own working e-mail server and my own mail domain! Some time there was no problems and I was glad to have an opportunity to have full control over my own mail flow.

But little bit later my ISP decided to make my Internet connection cheaper (for them) and they were assigned private IP address to my home Internet connection (192.168.192.2). As you can predict, from that moment my mail server was not reachable from real world and my mail domain was down.

First available solution was to point my MX record to some real mail server in real Internet and to use fetchmail or something like it ti fetch my email to home server. But this solution was not so flexible, and I decided to take one of IP addresses from IP pool of my employer (I am working for hosting company and company owner approved configuration described here) and to assign it to my home server to make my SMTP server available from real world. “It is impossible”, you can say, “You can not set foreign real IP to interface in PRIVATE network of another ISP!”. Yes, it is true, but using some tricks with Linux policy routing an some tunnelling I can do it! This article is about how it has been done by me.

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