07-16-2009 11:41 AM - edited 03-04-2019 05:27 AM
I am new to DMVPN but have performed extensive research to understand the ins and outs of this technology starting with phase 1, 2 and now phase 3. I have taken the time to understand the technology, each command, related syntax, design options and scalability considerations.
The command IP NHRP SHORTCUT appears in the phase-3 documentation and Cisco provides very little details on this command. Cisco has forgotten to provide real details on this option and it seems to be sort of important in spoke-to-spoke communications. Cisco's command lookup tool reveals nothing useful nor does a web search. I see IP NHRP REDIRECT is used on phase-3 HUBs -used to redirect spoke-to-spoke communication. Cisco documented this command fairly well; and these two commands always seem to appear together for phase-3.
Cisco Command tool
Usage Guidelines:
Do not configure this command if the DMVPN network is configured for full-mesh. In a full-mesh configuration the spokes are populated with a full routing table with next-hop being the other spokes.
Can anyone help?
Tks Frank
07-16-2009 12:23 PM
Hello Frank,
I've found this presentations taken from a networkers session
see slide 11
the RFC that defines NHRP is
http://www.faqs.org/rfcs/rfc2332.html
it speaks of a "short mode"
Probably it depends on scalability considerations and related choices.
it is not suggested where direct sopke to spoke tunnels should be built without going through the NHS/hub(s)
I think unless you are designing a very big DMVPN that you can use full mesh design.
Hope to help
Giuseppe
07-17-2009 07:35 AM
Thanks!!!!
I'll read through these details -
It's strange Cisco would not provide clear coverage on such an old technology.
Anyway, Thanks for assisting.
Frank
09-21-2009 02:57 PM
Hi Frank, I recommend the following reading.
http://blog.internetworkexpert.com/2008/12/23/dmvpn-phase-3/
Regards,
Mau
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