DMVPN shortcut and redirect

Answered Question
Feb 11th, 2009
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Hello,


I'm trying to understand the DVMPN Phase 3 and I'm trying get some clarification on the two commands:



ip nhrp redirect


ip nhrp shortcut



Based on what I have read (Shortcut Switching Enhancements for NHRP in DMVPN Networks) one thing i don't understand from this article:



"When using this feature, we recommend configuring the ip nhrp redirect command on all the DMVPN nodes. This configuration would be useful in the event the data traffic takes a spoke-to-spoke-hub-spoke path."



Why would you need redirect on all dmvpn nodes? How would you have a situation where traffic comes and leaves from the same interfaces on a spoke if the NHS and the summary route is pointing to the Hub router?



Is there some configuration i'm missing?



thank you in advance for your help.




Correct Answer by ggeorgas1 about 8 years 2 months ago

Hi


for a simple structured topology (See Diagram 1 below) I agree with your observation. Namely configure all hubs with ip nhrp redirect only and all spoke sites with ip nhrp shortcut.


(Diagram 1 - Simple Topology)


Hub 1 ------- Hub 2

! ! ! ! ! !

! ! ! ! ! !

S1 S2 S3 S4 S5 S6


Hub 1 and 2 configured with ip nhrp redirect only


Spoke S1 to S6 configured with ip nhrp shortcut only


However to cater for more complex topologies such as where the spoke may also be acting as a hub to other spokes, then I would imagine both ip nhrp redirect and ip nhrp shortcut would be required on these spoke/hub.


(Diagram 2 - Complex topology)


Hub 1---------Hub 2

! ! ! !

! ! ! !

S1 S2 S3 S4

! !

! !

S5 S6


S1 is a spoke to Hub 1

S1 is a hub to S5 and S6


Hence S1 would have ip nhrp redirect as well as ip nhrp shortcut enabled.


cheers

george

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Correct Answer
ggeorgas1 Wed, 03/04/2009 - 04:52
User Badges:

Hi


for a simple structured topology (See Diagram 1 below) I agree with your observation. Namely configure all hubs with ip nhrp redirect only and all spoke sites with ip nhrp shortcut.


(Diagram 1 - Simple Topology)


Hub 1 ------- Hub 2

! ! ! ! ! !

! ! ! ! ! !

S1 S2 S3 S4 S5 S6


Hub 1 and 2 configured with ip nhrp redirect only


Spoke S1 to S6 configured with ip nhrp shortcut only


However to cater for more complex topologies such as where the spoke may also be acting as a hub to other spokes, then I would imagine both ip nhrp redirect and ip nhrp shortcut would be required on these spoke/hub.


(Diagram 2 - Complex topology)


Hub 1---------Hub 2

! ! ! !

! ! ! !

S1 S2 S3 S4

! !

! !

S5 S6


S1 is a spoke to Hub 1

S1 is a hub to S5 and S6


Hence S1 would have ip nhrp redirect as well as ip nhrp shortcut enabled.


cheers

george

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