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Where I work we have a very old Linux machine that is doing our DNS/DHCP and other network services. That machine is our Default Gateway and all internet connections go through this computer somehow.

I'm a programmer not a network guy and I'm trying to gather information in order to replace that machine but I don't know what to call the service that 'provides a bridge to the Internet'.

My plan was to deploy a Synology server to handle our DNS/DHCP/Mail etc. We're not a big company so I think that would be enough. But I don't know if I can provide the same bridge to the internet because I don't know what its called.

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    The term you're looking for is probably "Router."
    – Hyppy
    May 19, 2015 at 18:04
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    Are you sure the TRAFFIC goes through this machine? It's very possible to have a machine that handles DNS and DHCP that does not also act as the gateway. Check the IP of your server and compare to the Gateway provided by the DHCP.
    – Machavity
    May 19, 2015 at 18:08
  • Alright ! Thanks. I suppose that there are services I need to install to configure a server to act as a router ? Would I be a fool to think that the server would automatically route the traffic to Internet ? May 19, 2015 at 18:09
  • @Machavity, yeah I think so. When I do a tracert (is that a good test ?) I see the machine in between my computer and the target IP. May 19, 2015 at 18:10
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    You should probably find someone willing to consult as a netadmin/sysadmin for this. There's a lot to screw up.
    – Hyppy
    May 19, 2015 at 18:13

2 Answers 2

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So here's the general overview of a conventional "residential gateway", or router.

You hook this device (WAN) to whatever your Internet source is (cable modem, DSL, etc). This public port gets the public IP. Then you hook all your devices to the LAN side. The device/server then does what's called Network Address Translation, where the LAN devices (via DHCP) get a non-routing IP and look to the router as the gateway (i.e. where the traffic comes in and goes out). This acts as a natural firewall because the devices behind the NAT are invisible unless you forward the public side to the private.

It sounds like you've got an actual computer doing this. So a simple router might not suffice. I would check to make sure they don't have any complex iptables set up to route the traffic. They might also have some specific DHCP set up to feed leases to specific devices.

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    It could also be an HTTP/HTTPS proxy, or deep packet inspection, or ad injection, or credit card sniffer, or web cache, or content filter, or any number of things.
    – Hyppy
    May 19, 2015 at 18:24
  • I don't think the machines are doing anything else than blindly routing traffic around. I'm going to to like @Hyppy said and talk to an outside network consultant to see if I can replace that machine with a normal router. May 19, 2015 at 18:43
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First of all: do not call it a "Bridge". This term has different meaning and may confuse people. What you need is called Router.

Modern OSes may do routing, but it is better to buy hardware router which is a special type of computer with little CPU (not an x86 probably) and specail build of OS (could be linux or proprietary os like IOS or ZynOS or RouterOS).

Hardware routers do not require much power, they are quiet (no fan needed) and have good tools to configure them (web or console-based).

Home/SmallOffice models are really cheap (Zyxel Keenetic for example). They do not support mail server, but DNS and DHCP are almost always supported.

You need the following information to choose router:

  • Type of WAN (Internet) connection: Ethernet, ADSL/ATM, PON etc
  • Connection method (some ISPs require VPN (PPTP or L2TP), PPPoE etc).
  • Number of users in your network.

You then choose router that supports all of that.

Sure you can buy server or even use PC for that. It will give you ability to install SMTP (email) server, Web server on it etc, but it is risky to have "everything on one server" and could be harder to configure. Stay with hardware router and install SMTP server on different machine, if you need.

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