User's Manual

Chapter 18 NAT
ISG50 User’s Guide
327
Port Mapping
Type
Use the drop-down list box to select how many original destination ports this NAT
rule supports for the selected destination IP address (Original IP). Choices are:
any - this NAT rule supports all the destination ports.
Service - this NAT rule maps one service to another.
Port - this NAT rule supports one destination port.
Ports - this NAT rule supports a range of destination ports. You might use a range
of destination ports for unknown services or when one server supports more than
one service.
See Appendix B on page 827 for some common port numbers.
Protocol Type This field is available if Mapping Type is Port or Ports. Select the protocol (TCP,
UDP, or Any) used by the service requesting the connection.
Original Port This field is available if Mapping Type is Port. Enter the original destination port
this NAT rule supports.
Mapped Port This field is available if Mapping Type is Port. Enter the translated destination
port if this NAT rule forwards the packet.
Original Start
Port
This field is available if Mapping Type is Ports. Enter the beginning of the range
of original destination ports this NAT rule supports.
Original End Port This field is available if Mapping Type is Ports. Enter the end of the range of
original destination ports this NAT rule supports.
Mapped Start
Port
This field is available if Mapping Type is Ports. Enter the beginning of the range
of translated destination ports if this NAT rule forwards the packet.
Mapped End Port This field is available if Mapping Type is Ports. Enter the end of the range of
translated destination ports if this NAT rule forwards the packet. The original port
range and the mapped port range must be the same size.
Enable NAT
Loopback
Enable NAT loopback to allow users connected to any interface (instead of just the
specified Incoming Interface) to use the NAT rule’s specified Original IP
address to access the Mapped IP device. For users connected to the same
interface as the Mapped IP device, the ISG50 uses that interface’s IP address as
the source address for the traffic it sends from the users to the Mapped IP
device.
For example, if you configure a NAT rule to forward traffic from the WAN to a LAN
server, enabling NAT loopback allows users connected to other interfaces to also
access the server. For LAN users, the ISG50 uses the LAN interface’s IP address
as the source address for the traffic it sends to the LAN server. See NAT Loopback
on page 328 for more details.
If you do not enable NAT loopback, this NAT rule only applies to packets received
on the rule’s specified incoming interface.
Firewall By default the firewall blocks incoming connections from external addresses. After
you configure your NAT rule settings, click the Firewall link to configure a firewall
rule to allow the NAT rule’s traffic to come in.
The ISG50 checks NAT rules before it applies To-ISG50 firewall rules, so To-ISG50
firewall rules do not apply to traffic that is forwarded by NAT rules. The ISG50 still
checks other firewall rules according to the source IP address and mapped IP
address.
OK Click OK to save your changes back to the ISG50.
Cancel Click Cancel to return to the NAT summary screen without creating the NAT rule
(if it is new) or saving any changes (if it already exists).
Table 103 Configuration > Network > NAT > Add (continued)
LABEL DESCRIPTION