Cisco 1701-K9-RF - 1701 ADSL Security Access Router : Datasheet : Page 144

Lab – Configuring Dynamic and Static NAT

Inside interfaces:

GigabitEthernet0/1

Hits: 16 Misses: 0

CEF Translated packets: 285, CEF Punted packets: 0

Expired translations: 11

Dynamic mappings:

-- Inside Source

[Id: 1] access-list 1 pool public_access refcount 4

pool public_access: netmask 255.255.255.224

start 209.165.200.242 end 209.165.200.254

type generic, total addresses 13, allocated 2 (15%), misses 0

Total doors: 0

Appl doors: 0

Normal doors: 0

Queued Packets: 0

Gateway# show ip nat translation

Pro Inside global Inside local Outside local Outside global

icmp 209.165.200.243:512 192.168.1.20:512 192.31.7.1:512 192.31.7.1:512

--- 209.165.200.243 192.168.1.20 --- ---

icmp 209.165.200.242:512 192.168.1.21:512 192.31.7.1:512 192.31.7.1:512

--- 209.165.200.242 192.168.1.21 --- ---

Note: This is only a sample output. Your output may not match exactly.

Reflection

1. Why would NAT be used in a network?

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Answers will vary, but should include: whenever there are not enough public IP addresses and to avoid the

cost of purchasing public addresses from an ISP. NAT can also provide a measure of security by hiding

internal addresses from outside networks.

2. What are the limitations of NAT?

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NAT needs IP information or port number information in the IP header and TCP header of packets for

translation. Here is a partial list of protocols that cannot be used with NAT: SNMP, LDAP, Kerberos version 5.