Dynamic Multipoint VPN (DMVPN) improves the usage of spoke-to-spoke networks. However, scaling of routing protocols and optimization of routing updates in large scale DMVPN networks remain a challenge. These challenges pertain to neighbor discovery, overhead reduction, and building upon the recent enhancements in the area of scaling routing over DMVPN. IPSEC tunnels, Next Hop Resolution Protocol (NHRP) and Enhanced Interior Gateway Routing Protocol (EIGRP) are established during initial startup of a DMVPN network. It is possible that EIGRP may not process and respond to inbound packets waiting in the interface or socket queue causing the spokes to time out and retransmit which worsens the resource contention issue. The EIGRP Scale for DMVPN feature provides an increase in the scalability of the hub device to 2500 sessions. The increase in the number of sessions reduces the adverse impact on CPU, system buffers, interface buffers, and queues and it reduces resource contention on the hub during initial startup of a DMVPN network. In a typical EIGRP DMVPN setup, spokes are configured as stubs.

This EIGRP Scale for DMVPN feature is enabled by default and does not have a configuration task.