Autorp Listener. I don't get the point....

I am confused over the autorp listener command. Now before you comment, I *know* that it enabled 224.0.1.39/40 to run in dense mode. However this is what I don't get.

Dense mode - floods all traffic out interfaces and waits for prunes if required.

Sparse mode - sender unicasts then mcasts traffic to the RP (it must know about before). If receiving traffic, then it must know about RP to send joins to the RP.

So with that in mind, people say that auto-rp kind of needs dense mode and won't work on pure sparse-mode setup. However, if I have 2 routers connected, both running sparse mode only, and both doing send-rp-announce to claim themselves as candidate RPs, then I see both routers have eachothers Routerx,224.0.1.39 paths in the mroute table. So if this was truly sparse mode behavior, how do they have eachothers announcements?

Secondly, I have labbed and found I can have SW2----R5----R4. All running sparse mode only, R5 send-rp-announce and SW2 send-rp-discovery. I look at R4 and it has the RP mappings! How does it receive this if everything is supposedly running in sparse?

So I hear people say about using the autorp-listener command, but I can't find out EXACTLY what it does. It doesn't seem to affect a routers ability to actually listen to auto-rp messages, am I right in thinking it's actual role is to FLOOD the received messages from one interface to another?

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Received on Sat Jan 01 2000 - 01:01:01 ARST