Q: how configure 2nd ethernet port to connect directly to airport extreme

If your Routers are connected by Ethernet, their Ethernet ports are typically combined into one network, based on the "main" Router issuing address for everything via DHCP, and the "secondary" Router set to "Bridge mode" to act as an Access Point (and NOT issue a new set of DHCP Addresses, which would create an unnecessary new Network).

In daily use, computer-to-computer or computer-to-printer traffic is recognized as "local" and is sent directly, station to station. Traffic bound for the Internet is sent to the "main" Router/Gateway, and the Router/Gateway acts as your agent on the Internet. So ONE "Router/Gateway" address on a Network is better.

To connect into this at any point, all that should be needed is to set the Ethernet port on your Mac to be the TopMost on the list in System Preferences > Network, and get an address via DHCP.

In general, your Routers should not rely on Wi-Fi as the only connection between them (you should have an Ethernet cable connecting each Router). If there is only a Wi-Fi connection between them, you burn up more than half ther potential over-the-air bandwidth on each Router just forwarding data to the other Router.

The other technique that many Routers can use is to rename each band (2.4 or 5GHz) on each Router to the SAME Network-name, and use the same encryption technique and password for each. This produces a Roaming Network, which in itself is no big deal because most folks don't roam around their houses getting passed off the different Wi-Fi sources. Its advantage is that you can use the BEST connection for each devices, regardless of band or Router connection, and the computer does the evaluation of which is "best".

Most Routers should be set to "automatic" channel selection of each band. When the Router powers up, it will choose the least bust channel available. If you find you need to manipulate the channel assignment, it is sometimes an indication you need a more-capable Router, or need to move the Router closer or add another Router to your Network (sound difficult, but can be very straightforward).

This article discusses all the options in detail. For a first read, look only at the diagrams in each section. Then go back and read more details on the setups that appeal to you.

Despite the article being extremely Apple centered, MANY different brands of Routers can be combined with Apple Routers to produce such cross-connected networks.

Wi-Fi base stations: Extending the range of your wireless network by adding additional Wi-Fi base stations - Apple Suppo…

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Wirelessly Extended Network (Wi-Fi connected base stations)

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