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I have a pretty standard 4 port ASDL router. I am running out of ports so wondering if I can piggback the spare 4 port router I have or if I need to purchase a new 8/16 port router. If it can be done, how is it done (I am sure it is simple, but so am I).

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up vote 5 down vote accepted

it's enough if you buy ethernet switch and connect it to one of lan ports of your router.

but yes - you can as well daisy-chain router behind router and have two layers of nat. but then communication between computers linked to first level router and those behind 2nd router will be a bit tricky.

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Moreover, the 4 ports physically in your router are just a switch. Plugging another switch into one of these is drop dead easy and makes everything completely transparent. – Scott Pack May 24 '09 at 13:16

The simple way, generally not requiring any configuration, is to chain the second router using one of the LAN-side ports. This means you only have 3 ports available, but it's the simple way. There are configuration changes (DNS, DHCP, etc) that need to be changed to do this 'properly'.

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As pQd said, probably the best solution is to buy a 8/16 port Ethernet switch and expand your existing network. If your needs grow again, you can take another port and connect another switch allowing you to expand further.

Just be careful if you connect switch-to-switch that you don't cause a STP loop. See this post for some more details:

The risk you will run by connecting one router to another is getting the routing setup properly. Most home 'routers' also act as firewalls which means you will be unable to communicate between the two networks without some additional configuration. You will also need to either run a routing protocol (RIP or OSPF probaby), or setup static routes so everything communicates properly.

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Yes, this is simple to do.

Ignore the WAN port on your secondary router, and plug one of your LAN ports on your main router into one of the LAN ports on your secondary router.

This will bring you up to 6 available ports without the need to reconfigure DNS/DHCP or anything else.

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that is tiny abuse but will work [ actually i do it at home - pigyback wireless rotuer to linux box that is actual router to use that as access point ]. but you should remember to disable dhcp on 2nd router. – pQd May 24 '09 at 13:33

The simplest way to do this is to put your second router in bridge mode. Simple (no extra NAT, no extra DHCP), quick and doesn't add another layer of complexity.

Routing protocols, STP or anything else is really overkill :-)

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