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Separate modem and router

Team Player

Hi good people.


I've recently upgraded from "Fast Broadband" ADSL to "Faster Fibre" VDSL. The service is great and super-fast, but ideally I'd like to have my modem and my router separate, so that I can put OpenWrt on my router.


I successfully separated my modem and my router when I was on ADSL, but then after ordering Faster Fibre, I realised that my existing modem didn't support VDSL, so I replaced it with a Netgear DM300, which supports both ADSL and VDSL. I successfully configured the DM300 to operate in modem-only mode while I still had ADSL prior to the fibre go-live, but after fibre go-live, I've had to slum it with the DM300 in modem-router-combined mode.


For a router I've got a couple of TP-Link Archer C5 AC1200's, one of which is currently on stock firmware and the other which is currently on OpenWrt Chaos Calmer. I'm aware that for TalkTalk VDSL, username and password is supposed to be blank and VLAN is supposed to be 101, but the Archer C5 stock firmware does not appear to have a menu option to configure this (I previously used the PPPoE option when I had ADSL, which worked fine). But my attempts to configure VLANs on OpenWrt for this purpose have left me unable to get into either the LuCi interface or the Dropbear interface, whoops (but I could still factory-reset it if necessary).


Any suggestions? Thanks.

Team Player

Well, I think I've cracked it - at least using the stock firmware of the Archer C5.


Basically, whilst the DM300 is still in Modem+Router mode, configure the relevant internet settings (not forgetting VLAN ID 101) - and then set it to Modem only mode *without* VLAN passthrough. Then, on the C5, set the WAN type to Dynamic (in other words, be a DHCP client).


And it works! The WAN-side IP address on the C5 is now the address I get from TalkTalk.


But there's a snag. I can no longer get into the DM300 web GUI - unless I change the WAN type on the C5 back to static, and put the IP address in the same subnet that I remember having set up on the LAN side of the DM300 (because the Netgear DM300 shuts down its DHCP server when you set it to Modem only mode, you see). Doing that shuts off the internet access, but the DM300 becomes accessible again, and from there, it's possible to change the DM300 back into Modem+Router mode and change any other config you might want.


Ideally I'd like to be able to get internet access from TalkTalk *and* get into my DM300 web GUI at the same time. But I guess that's what VLANs are for. I guess that disabling VLAN passthrough on the DM300 has the effect of removing the VLAN tagging before it passes the protocol messages onto your internal router - and that if you've got a router that can cope with VLANs (OpenWrt probably can but Archer C5 stock firmware can't, it seems) then perhaps you can do both.


Then again, my protocol understanding is that Ethernet will quite happily carry traffic from multiple IP subnets, even if it's not properly divided into VLANs, so there's probably some way around it.