How to set up NAT with overload on a serial connected network?

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May 13th, 2017
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My network looks like this: I have tried the normal way of configuring nat, that is to set the ip nat outside on the serial towards ISP and ip nat inside on the serial towards R2. I have also permitted both the serial network and LAN network connected to R2. I have also added a default route towards the ISP and a static route from the ISP towards the HQ. But I am still unable to ping the ISP from the host. 

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Reza Sharifi Sat, 05/13/2017 - 19:24
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2901 (r2) needs a default route towards 2901 (HQ) and 2901 (HQ) needs a default route towards the ISP. Also 2901 (HQ) needs a static route for PC and server subnet pointing to 2901 (r2).


Julio Moisa Sun, 05/14/2017 - 19:02
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You should have something like that on your 2901 HQ router

interface serial0/0
description TO-ISP

ip address

ip nat outside

interface serial 0/1
description TO-R2

ip address

ip nat inside

ip nat inside source list PRIVATE-NETS interface Serial 0/0 overload

ip route  name INTERNET

ip route <internal networks> <subnet mask> <IP of R2's next hop>

ip access-list standard PRIVATE-NETS

permit any

*To test you could create just a loopback on ISP router and nothing else, example:

interface lo 100
ip add

* Remember to use routing betwen HQ and R2 in order to advertise a default route and know how to reach the internal networks. 

Hope it is useful



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