Cabletron Systems SmartSwitch manual Dynamic NAT with Outside Interface Redundancy

Chapter 14: Network Address Translation Configuration Guide

Using Dynamic NAT with IP Overload

Dynamic NAT with IP overload can be used when the local network (inside network) will be initializing the connections using TCP or UDP protocols. It creates a binding at run time when the packet comes from a local network defined in the NAT dynamic local ACL pool. The difference between the dynamic NAT and dynamic NAT with PAT is that PAT uses port (layer 4) information to do the translation. Hence, each global IP has about 4000 ports that can be translated. NAT on the SSR uses the standard BSD range of ports from 1024-4999 which is fixed and cannot be configured by the user. The network administrator does not have to worry about the way in which the bindings are created; he/she just sets the pools and the SSR automatically chooses a free global IP from the global pool for the local IP.

Dynamic bindings are removed when the flow count goes to zero or the timeout has been reached. The removal of bindings frees the port for that global and the port is available for reuse. When all the ports for that global are used, then ports are assigned from the next free global. If no more ports and globals are available, the packets will be dropped.

Dynamic NAT with Outside Interface Redundancy

The following example configures a dynamic address binding for inside addresses 10.1.1.0/24 to outside addresses 192.50.20.0/24 on interface 192-net and to outside addresses 201.50.20.0/24 on interface 201-net:

Outbound: Translate source pool 10.1.1.0/24 to global pool 192.50.20.0/24

Translate source pool 10.1.1.0/24 to global pool 201.50.20.0/24

10.1.1.4

IP network 10.1.1.0/24

interface 192-net

		(192.50.20.0/24)
Router		Global Internet
et.2.1	et.2.2
	et.2.3

10.1.1.3

10.1.1.2

interface 10-net	interface 201-net
(10.1.1.1/24)	(201.50.20.0/24)

The first step is to create the interfaces:

interface create ip 10-net address-netmask 10.1.1.1/24 port et.2.1 interface create ip 192-net address-netmask 192.50.20.0/24 port et.2.2 interface create ip 201-net address-netmask 201.50.20.0/24 port et.2.3

230 SmartSwitch Router User Reference Manual