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My computer has two gigabit ethernet ports on the motherboard. Is it possible to have the OS (Win XP) combine them and treat as a single 2-gigabit connection? Failing that, is there any general advantage to just have both plugged in to my switch with two separate IP addresses?

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up vote 15 down vote accepted

Link Aggregation is the term that you're looking for, but in most home setups this is not possible. You need a switch that supports 802.3ad, and those are usually semi-expensive enterprise-class pieces of equipment. Assuming you have such hardware, you need a NIC that supports it as well.

Other terms for Link Aggregation include: NIC Teaming, Etherchannel, Port Channel, or trunking.

edit: To answer your last question, if you're on a standard home router and that is your only piece of networking equipment then there probably isn't much to gain from having 2 links.

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Windows XP doesn't natively support this but there are some motherboards that have link-aggregation capability, like Nvidia's Dualnet. Of course it's hardware specific and requires appropriate drivers. Here's one motherboard that has it:

There is this fellow who achieved a noteworthy increase in read/write speed,

Performance from the same workstation to the TS509 (neither teamed) was previously 45MB/s write, and about 60MB/s read. With the same workstation now configured with two gigabit LAN connections, the TS509 connected in the same manner, and the LACL trunks set up, I got a surprise. Write speeds jumped to 50MB/s and read speads are much higher at 83 MB/s using our 5.3GB test set of files.

but as MarkM says, it's not your normal home hardware.

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nVidia's dualnet doesn't make a single TCP/IP connection double in bandwidth. In a game-server scenerio like they draw out, there are usually multiple connections, allowing this to appear like it is 802.3ad Link Aggregation, but if there is only a single connection it will not give 2Gb/s unless the switch that is is connected to has 802.3ad configured. – MDMarra Aug 18 '09 at 0:03

No, there is not. Ethernet is a broadcast medium, so even if you could do this, both ports can't 'speak' at the same time. Furthermore, the routing for making this work would be complex and prone to failure.

Looks like I'm wrong, see below!

You could have two separate networks attached to your machine. So if you had two switches on two different networks, you could hook up one port to each switch. The primary use for a situation like this would be if you wanted to have one port be used for your external network traffic, and one port for purely local LAN-based traffic. But that's not really what you're trying to do. You want to use two ports to get a performance boost while speaking to a single external network, and that isn't going to work.

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Not accurate. Link Aggregation, which is what this question is describing, is common in many situations. Just usually not a home set up. – MDMarra Aug 17 '09 at 23:53
I never knew about this. Fascinating. Thanks for th ecorrection! – peterb Aug 18 '09 at 0:17
No problem. It is mostly used between core switches in a network where say 3-4Gbss are plenty and a 10Gb/s connection is too costly. Or for 3-4 10Gb/s connections where there really isn't an option other than the crazy expensive and obscure 40Gb/s links. Sometimes though, extremely high load servers will have it configured for internal applications. – MDMarra Aug 18 '09 at 1:12

micmcg is correct - these are the few reasons I can think of why a home user would want link aggregation:

  1. Each computer is link aggregated and is going to access a central point at once
  2. One computer is going to another with a RAID setup that allows transfer at the link aggregation speed (you are using RAID to go BEYOND normal gigabit speed)
  3. Multiple computers to one computer, definitely makes sense
  4. Most people don't understand saturation and bandwidth, hence why micmcg is stirring the pot
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Mostly this has been answered, however, you've still got 2 ports, you could always use the second port to connect to a device that you use a lot over a dedicated cross-over cable - perhaps a NAS. I'm fairly certain that a short direct cable will be faster than even the best switch/router

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The problem with that is that most home NASes only have a single port. If this was his only computer accessing a NAS, he probably would have gone with internal storage instead, as it is much cheaper and faster. – MDMarra Aug 18 '09 at 14:09

There are ways of connecting multiple connections. I have done it in my home using a program called Connectify Dispatch.
I have one connection plugged directly into my computer via cat 5 ethernet, and the other connection I pick up using an $15 Steren or Cisco usb wifi adapter. I then use the Connectify Dispatch program to join those connections into one. It does not double my download speeds but increased it from 200kbps to just over 350kbps. If you live in, for instance, a large apartment complex where there might be a dozen unsecured connections that you can can combine them ALL using Connectify Dispatch. I have heard of people getting up to 100mbps using this method. ( Connectify Demo video)

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