summarization

[miracle_david@yahoo.com]

Hi gentlemen, I wish to know whether I can use "summarization" in DMVPN all phases or not.

All the best

[Georg Pauwen]

Hello,

with 'summarization' you mean what exactly ? The 'ip summary-address eigrp' command that is used to advertise the default route on the hub ?

[miracle_david@yahoo.com]

Yes, exactly, both EIGRP & OSPF

[Georg Pauwen]

Hello,

I think route summarization can only be done in phase 1, as doing it for phase 2 and phase 3 would make all traffic between the spokes flow through the hub, which is exactly what you don't want when you configure phase 2 and 3.

[prasannakumarpalakollu78931]

It is often problematic for routers to maintain this volume of routes in their routing tables.

It is a method of representing a series of network numbers in a single summary address

[Deepak Kumar]

Hi,

Summarization is only useful in Phase1. Phase2 and Phase3 are not designed for summarization. 

if you looking solution to control queries and also advertising subnets from Branch LAN devices then use the newly added feature "WAN interface" in the eigrp.

[miracle_david@yahoo.com]

Firstly, why it's only useful to do this in 1st phase? Secondly, please explain your latter explanation in more detail about "newly added feature".

[Deepak Kumar]

Dear,

Phase 2 and Phase 3 are for the direct spoke to spoke communication. Phase 2 with the Routing table and Phase 3 with the NHRP. 

So Phase2 and Phase3 will be required routes for all your spokes also.  The summary prefix is advertised with the hub router as the next hop. Traffic between spokes yet again flows through the hub router – we’ve managed to destroy the most important property of Phase 2 DMVPN. (summarizing spoke routes on the tunnel interface of the spoke router is OK .... as is summarizing any non-spoke routes on the hub router.)

https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_eigrp/configuration/xe-3s/ire-xe-3s-book/ire-iwan-simpl.html#:~:text=The%20stub%20site%20ID%20is,incoming%20routes%20on%20WAN%20interfaces.&text=The%20eigrp%20stub%2Dsite%20command%20is%20mutu...

[miracle_david@yahoo.com]

You said "as is summarizing any non-spoke routes on the hub router". Do u mean it's ok to have summary on the HUB or not?

[Deepak Kumar]

Yes, 

Think if you have multiple subnets on the branch side then you can summarize on the branch side.