Cable modem forces double-NAT - Can I get rid of it?

[Gymnae]

Dear SNB Forum,

I've been lurking here for a couple of years and went ASUS and merlinWRT just for the input I gathered.

My network is a home network aiming at a minimum of cabling. Thus I run one cable from my force Cable router to my Asus WLAN router with a switch in between. But this causes a bit of problems, since now my WIFI Router is connected to the Internet through port LAN 1 and thus doesn't think it should do any WAN. If I plug the cable coming form the switch to WAN, my LAN network breaks down.

Please the see picture for a better explanation:

Is there any way that I can have the ASUS directly access the Internet and really route, being the only NAT device in the network without the need for a 2nd cable to run from the cable router via switch to Asus?

So far I imagine the only way I can make is to run a second set of LAN cables between cable router, switch and Asus, then to create a VLAN on the switch to separate the LAN cables doing only WAN from LAN. But maybe there's a chance to do it with the existing cabling.

Cheers

 

[PzASUS]

Hi,
I have the same set up but configured the right way. Just to understand, you just want your ASUS to be a router like it is meant to be, and the cable router is a modem? Is the modem just internet or TV also via coax to TV? Since not in the picture provided I am assuming the Cisco is just a cable modem. If that is the question then there are 2 options. Easy is to put modem into Bridged mode, connect ASUS WAN to Cisco LAN 1. If you can do that then log into ASUS and check WAN IP to verify you have an outside IP. If Bridged mode is available you wont know which LAN is the WAN on the Cisco when in bridged mode. Usually it is #1 you will have to check them manually if not LAN 1. If that works then connect switch to ASUS and LAN port. FYI always have your switch the last piece of equipment if using just to have more ports. Plus I am assuming this is an active switch. If that does not work then....

configure the modem by putting the ASUS IP in the DMZ, Enable DMZ hosting and add the ASUS fixed IP. Turn off wifi, DHCP on Cisco and run your wire to ASUS. Turn off any firewalls on Cisco but make sure the ASUS is the only connection to modem.Turn on firewall on ASUS.

Hope this makes sense. Your TP link could be causing problems if it is a router in switch mode. Active switching is best and inexpensive.

Good luck

 

[Gymnae]

Hope this makes sense. Your TP link could be causing problems if it is a router in switch mode. Active switching is best and inexpensive.

Good luck

Thanks for your input. To clarify:

1. Yes, the cable router should act as modem only and the Asus should do what it was born to do, but:
   
2. The Cable router cannot be put into switch mode - this has been deactivated by the ISP and won't be activated even after I have asked for it. They asked me to purchase an after market modem for that. Awesome.
3. DHCP is off in the cable router
   
4. The TP-Link is active switch and doesn't act as Router. It can be configured with VLANs, currently it's just "switching"
   
5. The current setup has the Asus Wifi Router's static IP in the DMZ of the cable router and the cable router is not doing an DHCPing
   
6. Cable modem, Asus and TP-Link switch are all in the same subnet with the Asus serving DHCP and all three devices having static IPs

I concur, it's "ugly" to have a switch in between my Asus Wifi-Router with DHCP and the Cable modem, but wiring wise I do not see another option. The cable outlet is in the living room and I want the Wifi-router in the main hallway for best reception. If I run a very long cable between Cable modem and Asus and then attach the switch to a LAN port of the Asus, I might solve my challenge, but I really want to avoid running a second cable if possible. See drawing for clarification.

PS: I think it's very cool that your first message is an answer, not a question like mine

 

[Gymnae]

I've decided that for now I want to go the traditional route. I read about potential solutions:

1. Splitting up the cable to create two cables running in one, but this among other problems reduces bandwidth
2. Dive into the abyss of iptables and create non-standard routing tables - which will be hell to maintain

Thus I just purchased a flat CAT7 cable to connect switch and Asus and I'll create a port based VLAN between the cable router and the asus via the switch. How convenient that it's a smart switch. See the updated diagram