1) no captures. At this stage it is purely educational and for my amusement
2) based on the dissection of several LIVE! presentations, articles, blogs and documentation I can almost assure that spoke 1 gets only the 1 redirect back that essentially tells it "you need to resolve the NBMA address of spoke 2". At that point a resolution request is sent from spoke 1 to W hub to C hub to E hub and finally to spoke 2. Due to NHRP shortcut spoke 2 initiates a tunnel back to spoke 1 and sends the NHRP reply over that tunnel. Spoke 1 now has the NBMA address of spoke 2 and presto So that is all good...I'm just hung up on HIW specifically the redirect procedure happens I'm almost confident that my hypothesis is correct - W hub sends the redirect to spoke 1 as soon as it realizes it is sending a packet out an interface with the same NHRP ID as the ingress tunnel - but I would love to know definitively My lab is tied up right now but if curiosity just won't die (and we all know it won't) I will lab this up Sent from my iPad On Dec 12, 2013, at 6:03 PM, Marko Milivojevic <mar...@ipexpert.com> wrote: Let me state: I have no idea. But two questions: 1) What do the packet captures say? 2) My *guess* would be that Spoke 1 gets a redirect from W-hub to C-hub once it forwards the packet. Then Spoke 1 will get another redirect when it sends another packet to C-Hub and the final redirect would be from an E-Hub when it sends the packet there. Then again, I have no idea what I'm talking about :-) On Thu, Dec 12, 2013 at 1:40 PM, Joe Astorino <joeastorino1...@gmail.com>wrote: > Say we have a hierarchical DMVPN environment. We have a west region > consisting of a hub and 2 spokes, an east region with a hub and 2 spokes > and a central hub tying it all together. The west and east hubs would each > have 2 tunnel interfaces - tunnel0 facing their local region and tunnel1 > facing up tot he central hub. The central hub would simply have tunnel0. > Everything would be configured with the same NHRP ID globally. > > I'm having a hard time understanding the control plan specifics of how > NHRP allows dynamic spoke to spoke tunnels between regions. I understand > the phase 3 concept (shortcuts and redirects) in a single region, but can't > piece it together for multiple regions. Basically, what I am struggling > with is this - If I am a host off a spoke in the west region and I wish to > reach a host off a spoke in the east region, ultimately what I want is a > dynamic spoke to spoke tunnel. We will call these spoke 1 and spoke 2 > here. > > - Spoke 1 gets the packet and routes it to the west hub. > - The west hub receives it on say tunnel0 and routes it out tunnel1 facing > up towards the central hub. > - The central hub only has a single tunnel0 interface. It receives the > packet in the same interface it hairpins it back out which from what I > understand is what triggers the NHRP redirect back towards the west hub. > > Ultimately though, we need the NHRP redirect message to actually hit the > original spoke so that the spoke in west can initiate an NHRP resolution > request for the spoke in East. This is where I get lost. How does the > redirect get to the spoke in west to begin with? My thought is that > perhaps the west hub actually sends the NHRP redirect to the spoke when it > sends a packet out another tunnel interface configured with the same NHRP > ID as the tunnel interface that received the packet. > > What am I missing? > > -- > Regards, > > Joe Astorino > CCIE #24347 > http://astorinonetworks.com > > "He not busy being born is busy dying" - Dylan > > _______________________________________________ > Free CCIE R&S, Collaboration, Data Center, Wireless & Security Videos :: > > iPexpert on YouTube: www.youtube.com/ipexpertinc >
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