connect 2 networks

Unanswered Question
Apr 6th, 2010

Hi buddies!

I need your expert advice...

I have 2 networks and I need able see diferent equipment on each network.

One network is fully administered, the other no.

The internet connection is plugged on FA0 and the other network on FA01.

the router is 1811 with IOS  12.4(6)T3

pls see the diagram.

thx for any comment.

I have this problem too.
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Jon Marshall Tue, 04/06/2010 - 13:04

What is the issue ? Do you have connectivity problems ?

What is the actual question


Federico Coto F... Tue, 04/06/2010 - 13:05


If the 1800 is the device with the public IP from the ISP, you should configure NAT for Internet access.

If you need outbound internet traffic that's pretty much (besides the basic connectivity configuration like the default gateway and properly configured interfaces).

You should create ACL to allow only the desired traffic to have a secure environment.

You can start with this.


Giuseppe Larosa Tue, 04/06/2010 - 13:06

Hello Joshu,

>> One network is fully administered, the other no.

We could call this an extranet. Security is the biggest issue you shouldn't accept any kind of traffic from them.

You should at least deploy extended ACLs and you should clearly define what IP subnets and what applications can be accessed by them.

Routing is not an issue unless there are overlapping addresses that would require the use of NAT, this may be among the first aspects to check.

Hope to help


josue Cabrera Tue, 04/06/2010 - 14:48

Thx everybody for answer!


Yes I have conectivity problems, I´m in the network when I send a ping to network  it fails.

The question will be, What is happening? why fails? I loss, I don´t know if is a ACL or NAT configuration.


I need establish comunication between networks.


Yes the 1800 have the public IP address (on the FE 0), and the internet access works without problems. But I can´t establish any connection to the other network (


No is an extranet, only is an other network, unfortunalety I have users in the other network (

Federico Coto F... Tue, 04/06/2010 - 15:03

To establish connections between both networks...  is the router the default gateway for both networks?

If so, you can communicate between both networks as long as there are no ACLs denying the traffic.


josue Cabrera Tue, 04/06/2010 - 15:08



For tthe network the defaul router is the 1800, for the other network have other default gw.

Federico Coto F... Tue, 04/06/2010 - 15:16

So, make sure that the other Default Gateway has a route pointing to the 1800 to reach the network on the other side of the 1800.


josue Cabrera Tue, 04/06/2010 - 15:29


here is a big issue... the other network administrator can´t access his router.

other idea?

Federico Coto F... Tue, 04/06/2010 - 15:32

If the other network has a default gateway to another router (and that router does not have a route to the 1800), the traffic cannot return.

If there's this routing problem on the other side, it has to be fixed.

Can do a test changing the default gateway on a computer to the 1800 (instead of the current default gateway, only if the LAN and the 1800 share the same subnet) and see if it works.


Paolo Bevilacqua Wed, 04/07/2010 - 06:50

Can you engage someone experienced to work with you on all the aspects ?

Evidently you miss the needed networking basics to solve this alone.


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