(Hah, looks like maybe my mobile had a misfire there.) I'm not sure what information you think the host is sending when it joins, but... a host is not required to send anything. It may send stuff. Hosts often do. But there's no host-joining-a-network protocol or anything.
NOX learns about a host's presence whenever that host sends *anything*. But if a host is quiet, NOX will never learn about it. Thus, it can easily be the case that a host is on the network and NOX has no idea. Thus, if someone wants to send to that host... NOX has no idea where it should be sending it. The two main options at this point would be: A) Drop (because you don't know where the destination is, or even if it exists at all), or B) Flood (which, if the destination exists, will definitely get the packet there). -- Murphy On Jul 23, 2012, at 7:37 PM, 王健 wrote: > But a host reports its own information when joins in the network, which I > observe according to NOX debug information. Does the topology will be > updated? If not, how does it update? Thank you very much. > > 在 2012-07-24 10:23:39，"Murphy McCauley" <[email protected]> 写道： > On Jul 23, 2012, at 7:19 PM, 王健 wrote: > >> Thank Murphy and Kyriakos for your patient reply, i am sorry that maybe i >> don't express my meaning clearly. When a host joins in the network, it >> receives the peridictly LLPP packet and reply its own information such as >> IP, MAC, access point to the NOX. Then the NOX update the topology >> immediately when it receives the host join in event, isn't it? If the >> toology is update immediately, then there is a quetion I can't think clealy. >> If host A sends an ICMP request to host B, the path_calculation_module says >> there is no route, it means there is no path between A and B, isn't it? If >> so, I think there is no need to broadcast. This confuses me a lot. I think >> maybe I was wrong somewhere, can you help me? > > I think you're saying that you expect the hosts to be receiving the LLDP from > the switch and then responding. This isn't the case. The hosts are not > expected to participate in the LLDP conversation -- it is strictly between > switches. > > > -- Murphy > >
