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Old 18th March 2010
ocicat ocicat is offline
Join Date: Apr 2008
Posts: 3,309

Originally Posted by Tramboi View Post
I infer if there were n external gateways with this technique, the pf machine would need n+1 network adapters.
I don't regularly answer questions in the FreeBSD subforae, but this portion of your questions is not necessarily FreeBSD-related.

While physically creating a router with n + 1 interfaces to connect n subnets to the Internet is possible, it is no longer the only option. You can accomplish the same topology with only two interfaces, but it requires more sophisticated configuration at the router & switch(es) as you will be configuring VLAN's (virtual LAN's). Limiting the router to two interfaces is also referred to a "router-on-a-stick" configuration. Googling for the term will give a place to begin. Wikipedia's entry on the subject: a bit sparse, but it is a start.

As for where to find what is necessary on the FreeBSD side, studying the ifconfig(8) manpage will be required. Studying vlan(4) may help as well.

But I should repeat: if your switch(es) do not support VLAN's, you will be limited to creating a router with n + 1 interfaces, however, most enterprise switches anymore support multiple VLAN's. Even some home switches (not hubs...) do as well.
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