Network address translation configuration issue

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Jan 16th, 2008
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IP want to apply Network address translation on my cisco router

i have 4 e1's and two ethernet interfaces, i want to utilize only one ethernet right now

I have 4 Public IPs on 4 E1s (virtual serial interface)in s a way

now i want to perform NAT in such a way that my (single)router's one ethernet port can translate

equally to 4 e1's in other words one private ip into 4 public addresses.

for one E1 i have done following configurations

#acces-list 1 permit x.x.x.x(prive 172)

#ip nat inside source list 1 int s0/0 overload

conf)#int giga 0/1

conf-if)#ip nat inside

conf)#int s0/0

conf-if)#ip nat outside

first please check, is above configuration is right for single translation?

now i want to apply this on 4 e1 (s0/0,s0/1/,s1/0,s1/1) please tell me configuration for his

write here


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Collin Clark Wed, 01/16/2008 - 12:50
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You do not need to apply "ip nat outside" on each individual serial interface. You can just apply once to your virtual interface. Also with "ip nat inside source list 1 int s0/0 overload" you should specify your virtual interface instead of s0/0.

HTH and please rate.

m_aurangzeb Wed, 01/16/2008 - 20:38
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I have done this on virtual interface as below but not working can u write commands here

aaccording to given below configuration, i am unable to ping from my Computer.

please tell me what is the purpose of overload command if i dont write it , then will it make any difference

interface GigabitEthernet0/1

description $ES_WAN$$FW_OUTSIDE$$ETH-WAN$

ip address x.x.0.1 (private IP pool)

no ip redirects

no ip unreachables

no ip proxy-arp

ip nat inside

ip route-cache flow

duplex auto

speed auto

no mop enabled

access-list 1 permit X.X.X.X. X.X.X.X (private IP pool

p nat inside source list 1 interface Serial0/0/0:0 overload

interface Serial0/0/0:0

bandwidth 2048

ip address x.x.x.x x.x.x.x (WAN IP)

ip nat outside

mohammedmahmoud Thu, 01/17/2008 - 00:16
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What about the routing part, are you using static routes (most commonly a default route) to point out to the serial interface. Before the NATing can be done, the router must route the packets to the outgoing interface.


Mohammed Mahmoud.

Collin Clark Thu, 01/17/2008 - 06:17
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Please post a sanitized config.


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