# NHRP Settings

In an AutoConnect-Virtual Private Network (AC-VPN) configuration, ScreenOS uses the Next Hop Resolution Protocol (NHRP) to enable the NHRP Server (NHS) to exchange information with the NHRP Clients (NHCs), and thus enable two NHCs to set up an AC-VPN on demand. (See AutoKey IKE VPN Tunnel Configuration.)

Enable NHRP: Check to enable the protocol.

NHC Setting: When configuring NHRP on the NHC, check this box and enter the NHS IP address.

NHS Setting: When configuring NHRP on the NHS, check this box, and select an ACVPN-Profile in the Profile drop-down menu.

Common Settings:

Hold Time: The length of time the NHS holds cached NHC information.

Max Query: The number of times the NHS queries the NHC when the NHC ceases to send updates.

Retry Interval: The number of seconds the NHS waits before sending another query.

Cache Setting: Click to enter NHC network information for the NHS to cache.