How to connect DD-WRT router's WAN port to computer?

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Leo28C
DD-WRT Novice


Joined: 02 Apr 2007
Posts: 11

PostPosted: Wed Jun 12, 2024 18:57    Post subject: How to connect DD-WRT router's WAN port to computer? Reply with quote
I'm trying to set up a hardware firewall to go between my modem and DD-WRT router. However the firewall machine can't seem to reach the router no matter what I try. I should at least be able to telnet into the ports I regularly access from the outside (those that are open in DD-WRT) but I get no response. It could be an issue on the firewall side but I want to make sure everything's fine on the DD-WRT side before I go back to losing hair fiddling with FreeBSD.

I have DD-WRT set to:

Connection Type: Static IP
WAN IP Address: 4.2.2.2/24
Gateway: 4.2.2.1
Static DNS 1: 192.168.1.78

I chose the 4.2.2.0/24 subnet randomly. I don't know what else one is supposed to do when there's no DHCP server on either side. Is this the correct way to go about it? In addition to the /24 above I've also tried /32 and even /23 with no success.

For reference, on the firewall side the network adapter is manually set to IP 4.2.2.1 subnet 255.255.255.0.

edit: I shouldn't need a crossover cable for this, right? Connecting a router's WAN port to a regular LAN port on a computer?
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kernel-panic69
DD-WRT Guru


Joined: 08 May 2018
Posts: 14506
Location: Texas, USA

PostPosted: Wed Jun 12, 2024 22:08    Post subject: Reply with quote
You may require a crossover cable between modem and firewall PC, but not PC and DD-WRT router. Need much more details about modem, ISP service, etc. For local side subnets, you must use a private IP address range.

https://stackoverflow.com/questions/81350/private-ip-address-ranges

https://en.wikipedia.org/wiki/Reserved_IP_addresses

https://www.subnet-calculator.com/

https://www.calculator.net/ip-subnet-calculator.html

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uvz123a
DD-WRT User


Joined: 01 May 2023
Posts: 52

PostPosted: Thu Jun 13, 2024 8:16    Post subject: Reply with quote
Network ports recognizes pinout and any UTP cable will work.
On older network cards you need to use correct cable, on newer this is not the case anymore.
You can use crossover or straight cable and it should work in any case.
Leo28C
DD-WRT Novice


Joined: 02 Apr 2007
Posts: 11

PostPosted: Thu Jun 13, 2024 10:08    Post subject: Reply with quote
kernel-panic69 wrote:
You may require a crossover cable between modem and firewall PC, but not PC and DD-WRT router. Need much more details about modem, ISP service, etc. For local side subnets, you must use a private IP address range.

https://stackoverflow.com/questions/81350/private-ip-address-ranges

https://en.wikipedia.org/wiki/Reserved_IP_addresses

https://www.subnet-calculator.com/

https://www.calculator.net/ip-subnet-calculator.html


I thought 4.x.x.x was a valid local subnet but I guess not? Huh. I'll go try addresses in the 10.x.x.x subnet instead and report back.

Modem and ISP are fine; the firewall PC is successfully connected to the outside. The issue here is between the firewall and router.

By the way I tried a crossover cable and it didn't change anything other than it showed up as 100mbit instead of 1gbit.
Leo28C
DD-WRT Novice


Joined: 02 Apr 2007
Posts: 11

PostPosted: Thu Jun 13, 2024 13:14    Post subject: Reply with quote
Leo28C wrote:
I thought 4.x.x.x was a valid local subnet but I guess not? Huh. I'll go try addresses in the 10.x.x.x subnet instead and report back.

Aaaand nope. I ended up using 192.168.2.0/24 subnet (192.168.2.1 for the firewall and 192.168.2.2 for the router) but got the exact same results as before.

I can't work on this again today sadly (shared internet) but tomorrow I'll try to set up a DHCP server on the firewall side and see if that works.
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