Re: DMVPN phase 3 example

Hi Marcin,

I haven't seen such example on Cisco website. However, I think you should
influence routing to get what you want.

DMVPN Phase 3 uses Redirects and CEF rewrite to accomplish spoke-to-spoke
connectivity. The main advantage is using CEF switching all the time (even
for the very first packet) and making spokes being a part of NHRP
resolution.

In your example this should work as follows.
1. Spoke1 prefers Hub1 (because of routing tuning) and tries to connect to
the network behind Spoke2.
2. As there is a prefix for the network behind Spoke2 in the routing table
pointing to the Hub1 (do not use "no ip next-hop-self eigrp" on the hub),
the first packet will be sent towards the Hub1.
3. Hub1 sees that packet and responds to Spoke1 with NHRP redirect message.
4. Spoke1 gets that message and sends the packet directly to the Spoke2
("directly" means still using Hub1 in this case, as there is no "better" CEF
entry yet).
5. Spoke2 gets the redirect message and contact Spoke1 directly using its
NBMA IP address.
6. Spoke1 gets a message from Spoke2 and sees the NBMA IP address of Spoke2
now. Then Spoke1 rewrites CEF entry for Spoke2's network (makes a
"shortcut").

As you can see there is still space for routing tunning (like changing
bandwidth on the tunnel interfaces when using EIGRP).

HTH,

--
Piotr Matusiak
CCIE #19860 (R&S, SEC)
Technical Instructor
MicronicsTraining.com
If you can't explain it simply, you don't understand it well enough -
Albert Einstein
2009/11/6 Marcin Zgola <MZgola_at_netrixllc.com>
> Any examples out there to run 2 hubs, and 2 spokes using DMVPN phase 3
> EIGRP.
>
> Where spoke 1 uses hub 1 as primary, and spoke 2 uses hub 2 as primary.
>
> I am comfortable setting this up using phase 2, where all you have to do
> is modify routing protocol to accomplish that.
>
> Since phase 3 uses NHRP for its packet switching , gets me little
> confused about setup like that.
>
> Thanks
>
>
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