Final answer:
You should disable Dead Peer Detection (DPD) if using a dynamic routing protocol and IPSEC VPNs.
Step-by-step explanation:
If using a dynamic routing protocol and IPSEC VPNs, you should disable Dead Peer Detection (DPD). DPD is a feature that checks the status of IPSEC VPN tunnels. However, in the case of dynamic routing protocols, such as OSPF or EIGRP, the VPN tunnel itself can go down temporarily due to routing changes. Disabling DPD prevents false alarms and unnecessary re-establishment of the VPN tunnel.