Secondary NIC: what all can I do?

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Problem :

I was loaned a NIC which I promptly installed in my F16 workstation just to ‘play’ with it (using iptables and stuff).

Other than forwarding packets from the new NIC to the old NIC using various iptables facilities, I don’t really know what else I can do with it? So, currently, I have disabled the new NIC because for some reason with both NICs enabled I couldn’t anymore get on the Internet.

Could I get some suggestions on what all things a dual-homed machine can do…? and what all I can learn while this loaner hardware lasts? Any links to a good self-learning resource online would be greatly helpful also.

Solution :

With two NICs you can

  1. use bonding and configure both NICs for your network. Then you can use it for failover (if the primary NIC fails, your system continues to use secondary NIC), or for load-balancing (traffic will be split between two NICs to double the bandwidth)
  2. separate your internal / external network. If you have clients accessing your dual-NIC server, you can easily use that for controlling the traffic allowed for them.
  3. have two separate network providers and if one of them goes down, still have one of them left so your entire traffic does not stop.

See Linux Advanced Routing & Traffic Control for more info.

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