Cisco Systems RV016, RV042G manual

VPN	9
Setting Up a Gateway to Gateway (Site to Site) VPN

-AH Hash Algorithm: The AH (Authentication Header) protocol describes the packet format and default standards for packet structure. With the use of AH as the security protocol, protection is extended forward into the IP header to verify the integrity of the entire packet. Check the box to use this feature. Then select an authentication method: MD5 or SHA1. MD5 produces a 128-bit digest to authenticate packet data. SHA1 produces a 160-bit digest to authenticate packet data. Both sides of the tunnel should use the same algorithm.

-NetBIOS Broadcast: NetBIOS broadcast messages are used for name resolution in Windows networking, to identify resources such as computers, printers, and file servers. These messages are used by some software applications and Windows features such as Network Neighborhood. LAN broadcast traffic is typically not forwarded over a VPN tunnel. However, you can check this box to allow NetBIOS broadcasts from one end of the tunnel to be rebroadcast to the other end.

-NAT Traversal: Network Address Translation (NAT) enables users with private LAN addresses to access Internet resources by using a publicly routable IP address as the source address. However, for inbound traffic, the NAT gateway has no automatic method of translating the public IP address to a particular destination on the private LAN. This issue prevents successful IPsec exchanges. If your VPN router is behind a NAT gateway, check this box to enable NAT traversal. Uncheck the box to disable this feature. The same setting must be used on both ends of the tunnel.

-Dead Peer Detection (DPD): Check the box to enable the router to send periodic HELLO/ACK messages to check the status of the VPN tunnel. This feature can be used only when it is enabled on both ends of the VPN tunnel. Specify the interval between HELLO/ACK messages (how often you want the messages to be sent).

Tunnel Backup: When DPD determines that the remote peer is unavailable, this feature enables the router to re-establish the VPN tunnel by using either an alternative IP address for the remote peer or an alternative local WAN interface. Check the box to enable this feature. Then enter the settings described below. This feature is available only if Dead Peer Detection is enabled.

Remote Backup IP Address: Specify an alternative IP address for the remote peer, or re-enter the WAN IP address that was already set for the remote gateway.

Cisco Small Business RV0xx Series Routers Administration Guide 137