Cisco Updated 300-410 Exam Questions and Answers by danny

After two OSPF neighboring routers establish bi-directional communication and complete DR/BDR

election (on multi-access networks), the routers transition to the exstart state. In this state, the

neighboring routers establish a master/slave relationship and determine the initial database descriptor

(DBD) sequence number to use while exchanging DBD packets.

Neighbors Stuck in Exstart/Exchange State

The problem occurs most frequently when attempting to run OSPF between a Cisco router and another

vendor’s router. The problem occurs when the maximum transmission unit (MTU) settings for

neighboring router interfaces don’t match. If the router with the higher MTU sends a packet larger that

the MTU set on the neighboring router, the neighboring router ignores the packet.

We have an example of how to configure DMVPN Phase II and we show the configuration here for your reference:

Diagram Description automatically generated

DMVPN Phase II – Dynamic Mapping

Text Description automatically generated

Note: Although Phase II – Dynamic Mapping is “dynamic” but we still need to add a static entry for the hub because without that entry, the NHRP registration cannot be sent.