Motorola NVG510, Administrator'S Handbook

Page: 58 / 152

Administrator’s Handbook
58
Link: IP Passthrough
When you click the
IP Passthrough
button, the
IP Passthrough
page appears.
IP Passthrough
The IP Passthrough feature allows a single PC on the LAN to have the Router’s public address assigned to it. It
also provides PAT (NAPT) via the same public IP address for all other hosts on the private LAN subnet. Using IP
Passthrough:
◆ The public WAN IP is used to provide IP address translation for private LAN computers.
◆ The public WAN IP is assigned and reused on a LAN computer.
◆ DHCP address serving can automatically serve the WAN IP address to a LAN computer.
When DHCP is used for addressing the designated passthrough PC, the acquired or configured WAN address
is passed to DHCP, which will dynamically configure a single-servable-address subnet, and reserve the
address for the configured PC’s MAC address. This dynamic subnet configuration is based on the local and
remote WAN address and subnet mask. If the WAN interface does not have a suitable subnet mask that is
usable, for example when using PPP or PPPoE, the DHCP subnet configuration will default to a class C sub-
net mask.
◆ The Passthrough DHCP Lease – By default, the passthrough host's DHCP leases will be shortened to two
minutes. This allows for timely updates of the host's IP address, which will be a private IP address before the
WAN connection is established. After the WAN connection is established and has an address, the passthrough
host can renew its DHCP address binding to acquire the WAN IP address. You may alter this setting.
◆ Click
Save
. Changes take effect immediately.
A restriction
Since both the Router and the passthrough host will use the same IP address, new sessions that conflict with
existing sessions will be rejected by the Router. For example, suppose you are a teleworker using an IPSec tunnel
from the Router and from the passthrough host. Both tunnels go to the same remote endpoint, such as the VPN
access concentrator at your employer’s office. In this case, the first one to start the IPSec traffic will be allowed;
the second one – since, from the WAN, it's indistinguishable – will fail.