wan subnet conflicts with lan subnet

June 20, 2012 at 10:21:02
Specs: Windows 7
i m trying to connect two routers a Cisco DPC3825 (r1) and DIR-655 (r2) and at the end getting the above error. i have disabled the SPI firewall on r1 and connected an ethernet cable lan to lan between the two. i don't want to confuse with whatever the mess i have done previously, just plz tell me step by step what i should do to connect these two routers, i would really appreciate it. bunch of thanks in advance :)
PS: in addition, the gateway ip of r1 is 192.168.0.1 with subnet mask of 255.255.254.0 and the gateway ip of r2 is 192.168.0.2 with subnet mask of 255.255.255.0. r1 has a ip range of 192.168.0.10 to 192.168.0.128 while r2 has range of 192.168.0.100 to 192.168.0.199.

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#1
June 20, 2012 at 10:39:21
Given those ip address its clear you don't understand NAT [network address translation].

A simple rule you need to remember.
Each wan and lan subnet has to be differnet for NAT to work

So if of r1 WAN is 192.168.0.1 with subnet mask of 255.255.254.0
than its LAN needs to be 192.168.1.1 subnet 255.255.255.0
in turn this means
r2 WAN is 192.168.1.2 and its LAN is 192.168.2.1

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#2
June 20, 2012 at 11:01:24
thanks Wanderer for the prompt reply. this is my first time i have ever tried this and yes i dont have understanding of NAT. just to clear onething as i said above,

""""the gateway ip of r2 is 192.168.0.2 with subnet mask of 255.255.255.0. r1 has a ip range of 192.168.0.10 to 192.168.0.128 while r2 has range of 192.168.0.100 to 192.168.0.199 """"

by the word RANGE i mean its the DHCP server ip range.

if you dont mind, what should i do next to get this done step by step?

thanks


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#3
June 20, 2012 at 11:04:37
we call that range a dhcp scope and that is just fine. You can't use that range though.

You would use 192.168.2.100 to 200 for example

To complete this setup just follow the ip addressing I laid out for you.

If there a reason why you are making this doubling hard with two routers?

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#4
June 20, 2012 at 11:10:47
alright i m trying to cope up this, the reason is i dont have access to the r1 and only one LAN is available to me. i could extend it with a simple switch (which i dont have :) but i do have an extra router and thats where all these problems generated.

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#5
June 20, 2012 at 11:31:57
That makes sense.

Set your routers wan port to dhcp. It will automactically get a ip address. Set your lan to 192.168.2.1 so NAT works. Make your routers dhcp scope 192.168.100-199

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#6
June 20, 2012 at 13:50:12
holyyy macro it just worked itself and i didnt do anything much.

let me explain what happend; i connected my laptop directly with the r1 LAN (primary router) and changed the ip address of my laptop LAN card to static ip 192.168.2.1 . i also disconnected from r1 wireless while doing above thingy. so the moment i changed the ip, i got disconnected form internet.

so i just blindly reconnected the r1 LAN to r2 LAN (which i did multiple times before but no success), went back to the laptop LAN card setup and switched it back to Dynamic instead of bove static configuration. and it workedddd :)

now my question is, since i m totally blind in this regard, can you explain what really happend that the connection suddenly turned successful? i m really surprised


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#7
June 20, 2012 at 14:08:36
You weren't suppose to change your lan ip on the nic. You were supposed to get the ip from your router in that range.

What you did is an alternative configuration if you want both routers in the same subnet.

But since you didn't follow a how you, you missed some steps and now you have no access to your router and it can cause a dhcp conflict on the network.

You also have no privacy/security like you would have if you were using NAT on R2

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