CCNA LAB Practice - III. Overload NAT (PAT)

iii. Overload NAT (PAT)

In the Overload NAT, we map the many Private IP Addresses to 1 Public IP Address.

Diagram

Procedure

1. Configuring & Assigning the IP addresses on the routers R1 & R2.
2. Check the routing table on both the routers.
3. Enable the routing protocol on both routers so that hosts on the both routers can communicate with each other.
4. Check the routing table on both the routers after enabling the routing protocol on both sides.
5. Make a web server to the host C & Run the Sniffer.
6. Defines a pool of global addresses to be allocated as needed.
7. Defines a standard IP access list permitting those inside local addresses that are to be translated.
8. Establishes dynamic source translation, specifying the access list defined in the prior step.
9. Marks the interface as connected to the inside & outside networks.
10. Verifying the Standard Dynamic translation by commands & Sniffer Outputs.

Configuration         

Step 1(A): Assigning the IP addresses on the Router R1.

R1(config)#interface serial 0

R1(config-if)#ip address 15.0.0.1 255.0.0.0

R1(config-if)#no shutdown

R1(config-if)#clock rate 64000   (Clock Rate will set only DCE Interface)

R1(config-if)#exit

R1(config)#interface ethernet 0

R1(config-if)#ip address 10.0.0.20 255.0.0.0

R1(config-if)#no shutdown

R1(config-if)#end

Step 1(B): Assigning the IP addresses on the Router R2.

R2(config)#interface serial 0

R2(config-if)#ip address 15.0.0.2 255.0.0.0

R2(config-if)#no shutdown

R2(config-if)#end

R2(config)#interface ethernet 0

R2(config-if)#ip address 20.0.0.2 255.0.0.0

R2(config-if)#no shutdown

R2(config-if)#exit

Step 2(A): Check the Routing table of the Router R1.

RA#sh ip route

C    10.0.0.0/8 is directly connected, Ethernet0

C    15.0.0.0/8 is directly connected, Serial0

Step 2(B): Check the Routing table of the Router R2.

RB#sh ip route

C    20.0.0.0/8 is directly connected, Ethernet0

C    15.0.0.0/8 is directly connected, Serial0

Step 3(A): Enable the RIP protocol on the Router R1.

RA(config)#router rip

RA(config-router)#network 10.0.0.0 (Networks to be advertised)

RA(config-router)#network 15.0.0.0 (Networks to be advertised) 

Step 3(B): Enable the RIP protocol on the Router R2.

RB(config)#router rip 10

RB(config-router)#network 20.0.0.0 (Networks to be advertised)

RB(config-router)#network 15.0.0.0 (Networks to be advertised) 

Step 4(A): Check the Routing table of the Router R2 after enabling RIP.

RA#sh ip route

R    20.0.0.0/8 [120/1] via 15.0.0.2, 00:04:42, Serial0

C    10.0.0.0/8 is directly connected, Ethernet0

C    15.0.0.0/8 is directly connected, Serial0

Step 4(B): Check the Routing table of the Router R2 after enabling RIP.

RB#sh ip route

C    20.0.0.0/8 is directly connected, Ethernet0

R    20.0.0.0/8 [120/1] via 15.0.0.1, 00:01:12, Serial0

C    15.0.0.0/8 is directly connected, Serial0

Step 5(A): Make a Web Server to the Host C & Run the Sniffer.

1. Make a Web Page & Save it on Desktop.
2. Go to Start Button > All Programs > Administrative Tool > Internet Service Manager
3. Right Click on the Computer name & goes to New tab > Web Site.
4. Follow the wizard and make the Web Server.
5. Run the Sniffer & capturing the www traffic.

Step 6: Defines a pool of global addresses to be allocated as needed.

R1(config)#ip nat pool cttc 15.0.0.200 15.0.0.200 prefix-length 8

Step 7: Defines a standard IP access list permitting those inside local addresses

                 that are to be translated.

R1(config)#access-list 1 permit 10.0.0.0 0.255.255.255

Step 8: Establishes dynamic source translation, specifying the access list defined

                 in the prior step.

R1(config)#ip nat inside source list 1 pool cttc overload

Step 9(A): Marks the interface as connected to the Inside Network.

R1(config)#int Ethernet 0

R1(config-if)#ip nat inside

Step 9(B): Marks the interface as connected to the Outside Network.

R1(config)#int serial 0

R1(config-if)#ip nat inside

Step 10(A): Verifying the Overload NAT Translation on Router R1 by

                          debugging command..

R1#debug ip nat

IP NAT debugging is on

When Host ’A’ pings to Host ‘C’:

00:38:03: NAT: s=10.0.0.1->15.0.0.200, d=20.0.0.1 [440]

00:38:03: NAT: s=20.0.0.1, d=15.0.0.200->10.0.0.1 [406]

00:38:03: NAT*: s=10.0.0.1->15.0.0.200, d=20.0.0.1 [442]

00:38:03: NAT*: s=20.0.0.1, d=15.0.0.200->10.0.0.1 [407]

00:38:03: NAT*: s=10.0.0.1->15.0.0.200, d=20.0.0.1 [443]

00:38:04: NAT*: s=20.0.0.1, d=15.0.0.200->10.0.0.1 [408]

00:38:05: NAT*: s=10.0.0.1->15.0.0.200, d=20.0.0.1 [445]

00:38:06: NAT*: s=20.0.0.1, d=15.0.0.200->10.0.0.1 [409]

When Host ’B’ pings to Host ‘C’:

00:38:34: NAT*: s=10.0.0.2->15.0.0.200, d=20.0.0.1 [499]

00:38:34: NAT*: s=20.0.0.1, d=15.0.0.200->10.0.0.2 [415]

00:38:34: NAT*: s=10.0.0.2->15.0.0.200, d=20.0.0.1 [500]

00:38:34: NAT*: s=20.0.0.1, d=15.0.0.200->10.0.0.2 [416]

00:38:34: NAT*: s=10.0.0.2->15.0.0.200, d=20.0.0.1 [502]

00:38:39: NAT*: s=20.0.0.1, d=15.0.0.200->10.0.0.2 [417]

00:38:39: NAT*: s=10.0.0.2->15.0.0.200, d=20.0.0.1 [509]

00:38:39: NAT*: s=20.0.0.1, d=15.0.0.200->10.0.0.2 [418]

Step 10(B): Verifying the Dynamic NAT Translation on Router R1 by

                           translation table.

R1#show ip nat translations

Pro      Inside global         Inside local      Outside local    Outside global

tcp    15.0.0.200:1041    10.0.0.1:1041      20.0.0.1:80        20.0.0.1:80

tcp    15.0.0.200:1042    10.0.0.2:1042      20.0.0.1:80        20.0.0.1:80

Step 10(C): Verifying the Dynamic NAT Translation by Sniffer Output by

                          accessing the Web Server from Host ‘A’.

  

Step 10(D): Verifying the Dynamic NAT Translation by Sniffer Output by

                          accessing the Web Server from Host ‘B’.