Cisco Router Challenge 74
Unit 7 Introduction to WANs: NAT
Outline
This challenge
involves the configuration of TCP load distribution for NAT. The objectives of this challenge are to:
Example
> en
# config t
(config)# access-list 7 permit host
195.11.220.2
(config)# ip nat pool globalnat 208.132.69.7 208.132.69.57 netmask
255.255.192.0 ?
type Specify the pool type
<cr>
(config)# ip nat pool globalnat 208.132.69.7 208.132.69.57 netmask
255.255.192.0 type ?
match-host Keep host numbers the same after
translation
rotary Rotary address
pool
(config)# ip nat pool globalnat 208.132.69.7 208.132.69.57 netmask
255.255.192.0 type rotary
(config)# ip nat inside destination
list 7 pool mynatpool
(config)# int e0
(config-if)#
ip nat
inside
(config-if)#
int s0
(config-if)#
ip nat
outside
Explanation
TCP Load Distribution is used where there is a pool of servers, and the NAT
translation assigns the mapping to one of these, in order to even the load. The
command:
(config)# ip nat pool globalnat 208.132.69.7 208.132.69.57 netmask
255.255.192.0 type rotary
defines that the addresses should be assigned to the pool. For example the
translations would be:
Inside Local Inside Global
1st: 208.132.69.7
<- 195.11.220.2
2nd: 208.132.69.8 <- 195.11.220.2
3rd: 208.132.69.9 <- 195.11.220.2
and so on. Thus when the first connection comes in for the address of
195.11.220.2, it will be translated to 208.132.69.7, the second for
208.132.69.8. Thus each of the servers will have a more equal loading. The
following command defines a dynamic destination translation (where normally NAT
would translate from a source node in the inside network):
(config)# ip nat inside destination
list 7 pool mynatpool