Thanks man, that actually helps me keep the logic straight. Obviously , the multicast ultimately is still going to be encapsulated in the tunnel so you would have a protocol stack looking something like this say with OSPF between tunnel peers (Let's assume ESP transport mode!)
[Outside IP] [ESP] [GRE] [Inside IP] [OSPF] [ESP Trailer] That is why specifying the public IP is confusing to me there because the destination address of the OSPF after the multicast gets changed to a unicast I think is going to be the tunnel address of the hub, say 172.16.1.1 to use your example. Perhaps when you specify the public IP, it maps it to the private IP based on the already existing ip nhrp map command On Fri, Mar 16, 2012 at 3:24 AM, Piotr Matusiak <[email protected]> wrote: > I think this is to keep those commands straight :) > > I think this way. All NHRP map command are like 'ip nhrp map <priv> > <public>' so that on spokes you have: > > ip nhrp map 172.16.1.1 100.1.1.1 > > to map between priv-public IP address on the hub. And you also have (in case > of mGRE on the spoke) command: > > ip nhrp multicast 100.1.1.1 > > <multicast> is just a keyword specifying priv part. > > Similarly on Hub you have: > > ip nhrp map multicast dynamic which means send all multicast traffic to > dynamically learnt Public (NBMA) IP addresses of your spokes (from NHRP DB). > > I know, this is not enough technical answer :) Also, note that sending mcast > traffic over multipoint interface must have some replication features > enabled. In this case you instruct the router to send mcast traffic to Hub's > Public IP and this must be tunnel destination IP I suppose. > > Regards, > Piotr > > > > > 2012/3/16 Joe Astorino <[email protected]> >> >> Can anybody shed some light on understanding why the "ip nhrp map >> multicast" command on a spoke maps to the public NMBA IP and not the >> tunnel IP of the hub? >> >> I understand that it is used so that any broadcasts/multicasts sent >> out the interface get sent to the hub only just trying to understand >> why the NBMA address is used. >> >> Any tips on how do you keep straight which NHRP commands use the >> tunnel IP vs the NBMA IP? >> >> -- >> Sent from my mobile device >> >> Regards, >> >> Joe Astorino >> CCIE #24347 >> http://astorinonetworks.com >> >> "He not busy being born is busy dying" - Dylan >> _______________________________________________ >> For more information regarding industry leading CCIE Lab training, please >> visit www.ipexpert.com >> >> Are you a CCNP or CCIE and looking for a job? Check out >> www.PlatinumPlacement.com > > -- Regards, Joe Astorino CCIE #24347 http://astorinonetworks.com "He not busy being born is busy dying" - Dylan _______________________________________________ For more information regarding industry leading CCIE Lab training, please visit www.ipexpert.com Are you a CCNP or CCIE and looking for a job? Check out www.PlatinumPlacement.com
