Cabletron Systems SSIM-R8-02 Spécifications télécharger pdf (Page 268)

Configuration Examples

248 Enterasys Xpedition User Reference Manual

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 XP 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 XP 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 DNS

The following example configures a DNS dynamic address binding for outside address

192.50.20.2-192.50.20.9 to inside addresses 10.1.1.0/24:

The first step is to create the interfaces:

et.2.2

(192.50.20.1/24)

et.2.1

(10.1.1.1/24)

Global Internet

IP network 10.1.1.0/24

Router

interface 10-net interface 192-net

DNS

DNS server static binding of 10.1.1.10 to 192.50.20.10

10.1.1.10

10.1.1.2 10.1.1.3

Server

interface create ip 10-net address-netmask 10.1.1.1/24 port et.2.1

interface create ip 192-net address-netmask 192.50.20.1/24 port et.2.2

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Cabletron Systems SSIM-R8-02 Spécifications Page 268