Is it possible to reuse routers to create additional LAN ports?

ITKE

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LAN

LAN port

Network design

Routers

Switches

Wireless

Can I daisy chain several routers together to add additional lan ports or will I get screwed up by their separate interfaces? We have several routers and no additional switches. If it will be an issue and I can not turn them into switches we will buy something but if we can reuse our existing garbage that would be great.

Asked: August 16, 2010 2:48 PM Last updated: August 21, 2010 8:57 AM

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Last updated: August 16, 2010 3:40 PM GMT

Matt Mather3,610 pts.
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- Matt Mather3,610 pts.

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Whilst routers can be used to perform switching functions and likewise some layer 3 aware switches can perform routing functions it is not really their intended purpose and best practice would dictate you shouldn’t do it.

If you were to look into this as a temporary measure for a small set of low bandwidth hosts then it would be acceptable but personally for anything else I would steer aware form it.

Another reason I say this is as well as it not adhering to best practices you won’t get the port density you require using a router as a switch and the throughput of older, sat in a box collecting dust, equipment is likely to be much lower than you think. Did you know a Cisco 2621XM for example will only push about 15Mbps?!

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pkpatel1151 Aug 18, 2010 11:22 PM GMT

I completely agree with mattmather. It is really a bad idea. Not only you will need to continue to create additional networks (a router will not allow use of smae network, eg. 192.168.100.0/24) on more than one port. So when you configure your first router with 192.168.100.1/24, the second port on the router will need to be on a different network, unless if you bridge two ethernet ports. i'd recommend buying a cheap switch if your budget does not aloow for a Cisco, to add port capacity.

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Chippy088 Aug 21, 2010 8:57 AM GMT

I am assuming you are using these for internal use, so these instructions are for internal use only. I have used several netgear routers from different ISPs and it is possible. There is a limit on what you can add to them as they only have 4 usable ports (not including the telephone port). This means that you can only connect 2 devices to each router down the chain, 1 port will be from the 'parent' router and 1 will be for the child. This lets you add 2 devices. You have to daisy chain the routers, so the main router can have 4 subrouters off it, (assuming it is the one connected to your ISP for internet access.) Each router attached has to be subnetted off the previous router (and the 2 devices you want to attach to it), so knowledge of routing and IP addresses is essential. Letting each router operate as a dhcp/dns server may not be what you want to do, if so, then you must give each device a static IP then, if RIP is enabled on each router, then the routing table RIP uses will be adequate. The hardest part is drawing the connection diagram, and subnetting the devices. You will need to know what will be attached to each subnet to plan the IP subnetting. Advantages of this are smaller collision zones, as there is less competition for routing on each subnet. And, as you thought, re-use of equipment. Disadvantages have already been mentioned in previous discussion. So long as you do not want high speed critic network communication, and only need low bandwidth usage (like internet browsing, and occasional downloading of files, MS updates will use the bandwidth) then it can be an acceptable alternative. If you still intend to do it, good luck. I will only stress that your subnetting skills need to be good.

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