Configuring NAT Examples

Dynamic Pool Configuration

The following example illustrates dynamic pool translation on the XSR, as shown in Figure 5-12.

Figure 5-12 Dynamic Pool Translation

Inside

 

 

 

Outside

 

 

Request

 

 

 

 

 

 

 

SA: 10.1.1.1

 

 

 

 

 

172.21.2.1

 

DA: 172.21.2.1

 

 

 

 

 

10.1.1.1

NAT Table

 

 

 

 

Reply

10.1.1.1

200.2.2.1

 

 

 

 

packet 1

 

After Translation

 

Reply after

 

DA: 200.2.2.1

After packet 1

 

DA: 172.20.2.1

 

SA: 172.21.2.1

reverse lookup

 

 

 

SA: 200.2.2.1

Internet

 

SA: 172.21.2.1

Internal

 

 

 

 

 

DA: 10.1.1.1

interface

 

 

 

 

 

 

 

XSR

 

 

 

 

 

 

 

 

External

 

 

 

Request

 

 

 

interface

 

 

 

 

 

 

 

 

 

 

packet 2

 

 

 

 

 

 

172.21.2.2

SA: 10.1.1.2

 

 

 

 

 

 

 

NAT Table

 

 

Reply

DA: 172.21.2.2

 

 

 

10.1.1.2

Reply after

10.1.1.1

200.2.2.1

After Translation

packet 2

DA: 200.2.2.2

 

reverse lookup

10.1.1.2

200.2.2.2

 

SA: 172.21.2.1

After packet 2

DA: 172.21.2.2

SA: 172.21.2.2

 

DA: 10.1.1.1

SA: 200.2.2.2

 

 

 

 

 

 

 

 

Configuring Dynamic Pool Translation

Dynamic pool translation, as shown in Figure 5-12, is performed through the following process:

1.The user at address 10.1.1.1 opens a connection to address 172.21.2.1

2.The first packet that the XSR receives from address 10.1.1.1 forces a NAT Pool table check. If no dynamic pool entry exists, and address 10.1.1.1 must be translated, then the XSR adds a pool entry. The router replaces the inside local address 10.1.1.1 with the inside global address 200.2.2.1, and forwards the packet. Any other connections originating from address 10.1.1.1 will use address 200.2.2.1 as the global address.

3.Host address 172.21.2.1 receives the packet, and responds to address 10.1.1.1 by using the inside global address 200.2.2.1.

4.When the XSR receives the packet, it searches its NAT Pool table, using address 200.2.2.1, translates the address to inside local address 10.1.1.1, and forwards it to address 10.1.1.1.

5.The same process applies to the connection originating from address 10.1.1.2, but a different global IP address is used.

Now enter the commands below to set dynamic pool translation. Note some steps are optional.

1.Create local IP pool NATpool with excluded IP addresses (optional) and quit Local Pool mode:

XSR(config)#ip local pool NATpool 200.2.2.0 255.255.255.0 XSR(ip-local-pool)#exclude 200.2.2.1 8 XSR(ip-local-pool)#exclude 200.2.2.21 233 XSR(ip-local-pool)#exit

2.Register the global NAT pool:

XSR(config)#ip nat pool NATpool

XSR User’s Guide 5-39

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Enterasys Networks X-PeditionTM manual Dynamic Pool Configuration, Configuring Dynamic Pool Translation