I want one of my routers to participate in the EIGRP routing. The problem is that I want to only
redistribute static route via EIGRP on that new router. I don't want to advertise the connected network via EIGRP.
However if I don't make any connected interfaces part of the EIGRP, the router doesn't advertise
and it doesn't see any neighbors. The question is how can I connect that router to the EIGRP 10 AS?
Can I use loopback interface to establish the EIRGP advertisements? I am not sure how the lookback
interfaces work so I need some kind of direction. Thanks as always!!!!
I can understand wanting to test with something that will not disrupt a production network. As I said if you have the router that you want to redistribute on and if you configure a single network statement for a physical intereface that will allow the router to form EIGRP neighbor relationship. And if you think about it, the router that you are using to test will not advertise anything at that point. (The router it connects to will advertise that physical subnet, but since that subnet does exist in the physical network will it have any negative impact to advertise that single physical subnet?)
After you have established the single EIGRP neighbor to the test router then the test router can redistribute the test static route. And that would be the only thing that it advertised.
You ask what loopback interfaces are used for in EIGRP and that is not a simple question. EIGRP will prefer to use a loopback interface address as its routerID. And that is the single real use of loopback that I can think of in EIGRP. Beyond its specific use in EIGRP loopback interfaces can be used for many things. A loopback interface gives you indipendence from physical interfaces, so if there is some address that you want to be always available (perhaps as the end point of a tunnel, or as the address used for network management, for telnet/SSH, for AAA authentication, as the source of log messages, etc) then it is helpful to use loopback interfaces addresses for things like this.