Media for C3845, Dual Hub Dual DMVPN Hub-To-Spoke, Limitations?

C3845, Dual Hub Dual DMVPN Hub-To-Spoke, Limitations?

Hello everyone,

we are currently designing a IPSec secured DH-DD 'hub-to-spoke only' DMVPN based on two C3845 routers, using EIGRP as the dynamic routing protocol, especially for providing the ISDN backup. The bandwidth per hub is about 30 Mbit/s.

Has anyone deeper experiences with this setup?

In several documentations (available under

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one can see, that cisco recommends only

350 spokes per mGRE-tunnel on the hub and two mGRE-tunnels per hub. It is also said, that this should be a limitation of the routing protocol.

For our design, which must be able to handle nearly 1500 C836-spokes with 1024/128 kbit/s ADSL lines this is far too less.

I wonder, why this limitation is so low and which part of the concept is responsible for that?

The spokes should be configered as "EIGRP stubs" and should only receive one summary-route from the hub. So routing traffic and -load should be at a minimum.

Unfortunately I have read some documentation, that said "route summarization" would not be possible in this scenario with DMVPN? (Why) is this the case? We only want Hub-to-Spoke routing, not spoke-to-spoke, so I do not understand this restriction.

Beside this, does anyone have some more information about "DMVPN Phase

3" and when that will be released?

Thanks in advance for your comments and hints,

Dennis Breithaupt