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New Member

Cisco 1841 Router - configuration


i am prasad, i am very new to routers family i have one 1841 router with 1 CSU/DSU card, 2 Ethernet port with 1 AIM VPN Card.

i want to configure NAT and DMZ zone using this router along with the feature of the 1841

Please suggest me how to proceed in this regards.


Re: Cisco 1841 Router - configuration

Hi Prasad ,

As you have two ethernet ports and one serial interface , you can have a private zone on one of the interface and use nat for internet access and other one you can use it as DMZ

you can refer this document for Nat

pls correct me if your question was on using Ipsec as you have a vpn card


vanesh k

New Member

Re: Cisco 1841 Router - configuration

hi vanesh,

Great man, Thank you very much for your quick response. You are right on target.

I don't have any serial port in my router, I have 1 T1 CSU/DSU card with 2 Ethernet ports. My router looks something similar to this (without HWIC 4ESW at slot1)

OK, i will configure slot0(T1 Card interface) and ETH0 for NAT and ETH1 for Private zone the router.

i have one more problem i.e i have one more router i.e. 1721 with 1 Ethernet and 2 Wan slots(0- T1 CSU/DSU 1-Empty)this router is provided by our ISP and 1721 router now serving the internet needs of mine. The 1841 is the new router which i am going place in between the 1721 and my LAN.

Please let me know the next step.(guys i am a system administrator working on Windows and Linux Platform i don't know much about CISCO routers sorry to bother you guys asking basic questions)

Re: Cisco 1841 Router - configuration

Hi prasad,

As you will have private ip addresses in your LAN , you need to do natting , so let me know wheter you will do natting in your router ie 1800 or the SP router ie 1700.

If you are going to do natting in your router , then you need to connect your router and SP router with a B2B ethernet connectivity and give a public address(To be obtained from the provider(/30) , so that you do a pat with the public address .

If you are going to do pat in the provider router , then you can have a private address in the B2B ethernet connectivity and do a pat with the public ip given on the wan link of the SP router .

And now the 1800 router is going to be inbetween ur LAN and SP router , so now you have got only one Ethernet interface , and if you a switch (2950 and higher models ) , then we can create two sub-interfaces in the 1800 router and have two Lans on the same ethernet.

pls let me know abt your thoughts


vanesh k