You are the network administrator of a company. The company’s office network needs to be connected to the Internet. The company only applies for a dedicated line from the ISP. The dedicated line is assigned a company IP address and is configured so that all hosts in the company can access the external network.
Technical principle
NAT divides the network into two parts, the internal network and the external network. When the LAN host uses NAT to access the network, it converts the local address inside the LAN into a global address (the legal IP address of the Internet) and then forwards the data packet; NAT is divided into two
types : NAT (Network Address Translation) and NAPT (Network Port Address Translation IP address corresponds to a global address).
NAPT: Use different ports to map multiple internal IP addresses to a specified external IP address, many to one.
NAPT uses port multiplexing. All hosts in the internal network can share a legal external IP address to access the Internet, thus saving IP address resources to the greatest extent. At the same time, it can hide all hosts inside the network, effectively avoiding attacks from the Internet. Therefore, the most widely used in the network is the port multiplexing mode.
ISP (Internet Service Provider), an Internet service provider, is a telecom operator that comprehensively provides Internet access services, information services and value-added services to the majority of users. ISP is a formal operating enterprise approved by the national competent authority and enjoys national legal protection.
Experimental procedure
Create a new Packet Tracer topology map
(1) R1 is the company's export router, which is connected to the ISP router through a V.35 cable serial port, and the DCE terminal is connected to R1, and its clock frequency is configured to be 64000; (2) Configure the PC, server and router interface IP addresses
;
(3) Configure a static routing protocol on each router so that PCs can ping each other;
(4) Configure NAPT on R1.
(5) Define internal and external network interfaces on R1.
(6) Verify the interoperability between hosts.
Laboratory equipment
PC 2 台；Server-PT 1 台；Switch_2950-24 1 台 Router-PT 2 台；直通线；交叉线；DCE串口线
PC1
192.168.1.2
255.255.255.0
192.168.1.1
PC2
192.168.1.3
255.255.255.0
192.168.1.1
Server
200.1.2.2
255.255.255.0
200.1.2.1
R1
en
conf t
host R1
int fa 0/0
ip address 192.168.1.1 255.255.255.0
no shutdown
int s 2/0
ip address 200.1.1.1 255.255.255.0
no shutdown
clock rate 64000
R2
en
conf t
host R2
int s 2/0
ip address 200.1.1.2 255.255.255.0
no shutdown
int fa 0/0
ip address 200.1.2.1 255.255.255.0
no shutdown
R1
exit
ip route 200.1.2.0 255.255.255.0 200.1.1.2
R2
exit
ip route 192.168.1.0 255.255.255.0 200.1.1.1
end
show ip route
PC1
CMD
ping 200.1.2.2 (success)
Web 浏览器
http://200.1.2.2 (success)
R1
int fa 0/0
ip nat inside
int s 2/0
ip nat outside
exit
access-list 1 permit 192.168.1.0 0.0.0.255
ip nat pool jaking 200.1.1.3 200.1.1.3 netmask 255.255.255.0 #设置名称为jaking的地址池，起始和终止IP都是200.1.1.3
ip nat inside source list 1 pool jaking overload (无 overload 表示多对多，有 overload 表示多对一)
end
show ip nat translations(无结果)
PC1
Web 浏览器
http://200.1.2.2 (success)
R1
show ip nat translations(有 1 个结果)
PC2
Web 浏览器
http://200.1.2.2 (success)
R1
show ip nat translations(有 2 个结果)
Practical exercise
R1
Continue with configuration dialog? [yes/no]: n
Press RETURN to get started!
Router>en
Router#conf t
Enter configuration commands, one per line. End with CNTL/Z.
Router(config)#host R1
R1(config)#int fa 0/0
R1(config-if)#ip add 192.168.1.1 255.255.255.0
R1(config-if)#no shut
%LINK-5-CHANGED: Interface FastEthernet0/0, changed state to up
%LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/0, changed state to up
R1(config-if)#int s 2/0
R1(config-if)#ip add 200.1.1.1 255.255.255.0
R1(config-if)#no shut
%LINK-5-CHANGED: Interface Serial2/0, changed state to down
R1(config-if)#clock rate 64000
R1(config-if)#
R2
Continue with configuration dialog? [yes/no]: n
Press RETURN to get started!
Router>en
Router#conf t
Enter configuration commands, one per line. End with CNTL/Z.
Router(config)#host R2
R2(config)#int s 2/0
R2(config-if)#ip add 200.1.1.2 255.255.255.0
R2(config-if)#no shut
%LINK-5-CHANGED: Interface Serial2/0, changed state to up
%LINEPROTO-5-UPDOWN: Line protocol on Interface Serial2/0, changed state to up
R2(config-if)#int fa 0/0
R2(config-if)#ip add 200.1.2.1 255.255.255.0
R2(config-if)#no shut
%LINK-5-CHANGED: Interface FastEthernet0/0, changed state to up
%LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/0, changed state to up
R2(config-if)#
R1
R1(config-if)#exit
R1(config)#ip route 200.1.2.0 255.255.255.0 200.1.1.2
R2
R2(config-if)#exit
R2(config)#ip route 192.168.1.0 255.255.255.0 200.1.1.1
R2(config)#end
R2#
%SYS-5-CONFIG_I: Configured from console by console
R2#show ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area
* - candidate default, U - per-user static route, o - ODR
P - periodic downloaded static route
Gateway of last resort is not set
S 192.168.1.0/24 [1/0] via 200.1.1.1
C 200.1.1.0/24 is directly connected, Serial2/0
C 200.1.2.0/24 is directly connected, FastEthernet0/0
PC1
CMD
ping 200.1.2.2 (success)
PC>ipconfig
IP Address......................: 192.168.1.2
Subnet Mask.....................: 255.255.255.0
Default Gateway.................: 192.168.1.1
PC>ping 200.1.2.2
Pinging 200.1.2.2 with 32 bytes of data:
Request timed out.
Reply from 200.1.2.2: bytes=32 time=24ms TTL=126
Reply from 200.1.2.2: bytes=32 time=25ms TTL=126
Reply from 200.1.2.2: bytes=32 time=20ms TTL=126
Ping statistics for 200.1.2.2:
Packets: Sent = 4, Received = 3, Lost = 1 (25% loss),
Approximate round trip times in milli-seconds:
Minimum = 20ms, Maximum = 25ms, Average = 23ms
PC>ping 200.1.2.2
Pinging 200.1.2.2 with 32 bytes of data:
Reply from 200.1.2.2: bytes=32 time=25ms TTL=126
Reply from 200.1.2.2: bytes=32 time=20ms TTL=126
Reply from 200.1.2.2: bytes=32 time=23ms TTL=126
Reply from 200.1.2.2: bytes=32 time=25ms TTL=126
Ping statistics for 200.1.2.2:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 20ms, Maximum = 25ms, Average = 23ms
Web browser
http://200.1.2.2 (success)
PC2
CMD
ping 200.1.2.2 (success)
PC>ipconfig
IP Address......................: 192.168.1.3
Subnet Mask.....................: 255.255.255.0
Default Gateway.................: 192.168.1.1
PC>ping 200.1.2.2
Pinging 200.1.2.2 with 32 bytes of data:
Reply from 200.1.2.2: bytes=32 time=31ms TTL=126
Reply from 200.1.2.2: bytes=32 time=17ms TTL=126
Reply from 200.1.2.2: bytes=32 time=19ms TTL=126
Reply from 200.1.2.2: bytes=32 time=23ms TTL=126
Ping statistics for 200.1.2.2:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 17ms, Maximum = 31ms, Average = 22ms
Web browser
http://200.1.2.2 (success)
R1
R1(config)#int fa 0/0
R1(config-if)#ip nat inside
R1(config-if)#int s 2/0
R1(config-if)#ip nat outside
R1(config-if)#exit
R1(config)#access-list 1 permit 192.168.1.0 0.0.0.255
R1(config)#ip nat pool jaking 200.1.1.3 200.1.1.3 netmask 255.255.255.0
R1(config)#ip nat inside source list 1 pool jaking overload
R1(config)#end
R1#
%SYS-5-CONFIG_I: Configured from console by console
R1#show ip nat translations
R1#
PC1
Web 浏览器
http://200.1.2.2 (success)
R1
show ip nat translations(有 1 个结果)
R1#show ip nat translations
Pro Inside global Inside local Outside local Outside global
tcp 200.1.1.3:1026 192.168.1.2:1026 200.1.2.2:80 200.1.2.2:80
PC2
Web 浏览器
http://200.1.2.2 (success)
R1
show ip nat translations(有 2 个结果)
R1#show ip nat translations
Pro Inside global Inside local Outside local Outside global
tcp 200.1.1.3:1026 192.168.1.2:1026 200.1.2.2:80 200.1.2.2:80
tcp 200.1.1.3:1024 192.168.1.3:1026 200.1.2.2:80 200.1.2.2:80
Summarize
So far, the network port address translation NAPT configuration using the Cisco simulator is completed.