Tue Sep 27, 2011 12:13 am
PPPoE connections get established before there's any DNS, or VRRP. Those work via IP address. You get an IP address via the PPPoE mechanism. Therefore PPPoE happens before IP, so you can't use IP load balancing mechanism to load balance PPPoE end points.
It's impossible to state how many users you can put on an RB1100. It depends on how many packets per second will traverse the router, and what it has to do to each packets. Will there be queueing? If so, simple queues or queue trees? Will there be firewalling? What else is the router doing? And so on. If you really, really, really want a number go with 750 connections per router. That should be safe. It's also a really wild and probably hopelessly inaccurate guess. The most important number is pps. Find out, and look at routerboard.com where the specs for each router state how many pps it can handle. Then figure out which tasks you're going to put on the router for each packet, and how it would impact load scenarios.
I'm not being difficult here. It sounds easy to ask "how many users can I put on this router", but you have to realize that it's an extraordinarily difficult question to answer, despite it sounding like such a simple question.
One router can of course terminate multiple broadcast domains, and can act as a PPPoE server for multiple broadcast domains.
Yes, PPPoE can make use of RADIUS just fine.