We recently had fibre installed. Slingshot sent us a Netcomm NF4V router for the connection. Unfortunately Chorus technicians severed our copper phone line when they installed fibre. So our phone goes through fibre. And Slingshot's solution is VoIP. The phone is delivered through NF4V as you may have known. NF4V is a good router. But it's not ideal as the engine of our home network because of its(lack of) processing power and some lack of functionality. For example, copying a file to/from a USB harddrive attached to NF4V gives you 4MB/s, mediocre wifi coverage, VPN, DDNS, etc. I decided to use a more powerful, more configurable Asus AC68u to be our main router. After a few days of confusion and banging my head, I got it all sorted. I'd like to share my experience in case someone might need to do the same thing.
1. AC68U to provide internet connection and Wireless Access.
2. Phone(VoIP) works. Because AC68U doesn't have the ability to handle VoIP, we still need NF4V to provide phone service. Some other people on Geekzone suggested SP122. But that's $100 I don't have. Besides why do you want to spend extra money when NF4V can deliver decent phone service?
3. Devices connecting to both AC68U and NF4V can see each other. Preferably they are on the same subnet. Otherwise some devices may have trouble discovering resources shared on another subnet. For example my TV will have trouble detecting Plex running on my PC.
Warning: Always backup your working router config before making any changes. Or you may feel sorry if you can't restore something.
For example I still haven't figured out how to add two PPPoE devices in NF4V after deleting them. The only way to get them back is by restoring from backups.
First challenge: connect to internet using AC68U. This is well covered in other discussions on Geekzone. It took me a few hours to figure it all out though. I won't repeat the steps here. Because I want to combine AC68U LAN and NF4V LAN as the same subnet, I disabled DHCP on NF4V. Also I only need AC68U to provide wireless, I disabled wireless on NF4V.
Second challenge: enable VoIP service. Because I'd like to make the whole home network in the same subnet, I thought I could connect LAN on NF4V to LAN on AC68U and route all traffic through AC68U like I do with my PC. This works for the PC if I set the gateway to AC68U. But VoIP seems to go through WAN on NF4V. Adding default gateway using an AC68U's IP doesn't work because 0.0.0.0/0 is considered illegal by NF4V. So I was unable to get it to work. Turning NF4V into bridgemode doesn't help either. It could be because my settings were not right. But I couldn't even get to the internet when NF4V was in bridgemode and AC68U's WAN connected to ONT directly.
However this exercise tells me I can create different types of WAN interfaces. To do that I also need to delete all existing WAN interfaces: ADSL, VDSL, Fibre.
Finally I find out that I can create a WAN interface on eth4. eth0 - eth3 on NF4V are LAN ports. eth4 is the WAN port. When creating this WAN interface on eth4, DO NOT use any PPP type. Just assign an IP to either manually or through DHCP running on AC68U. Once this is done, the world suddenly brightens.
Now I connect the WAN port on NF4V to a LAN port on AC68U, a couple of minutes later, the phone LED on NF4V lights up. Phone is at my service!
Third challenge: combine AC68U LAN and NF4V LAN. Because I want them to be on the same subnet, I turned off NAT on NF4V. But I can't connect to NF4V LAN from AC68U. However if I change the LAN on NF4V to another subnet, turn on NAT, and add a static route in AC68U, then devices on AC68U can access those that link to NF4V. Trouble is TV is not happy. Then I realise I just need to treat the four LAN ports as a switch for AC68U. So I assign an IP in AC68U's subnet to NF4V's br0. Connect a LAN port on AC68U to a LAN port on NF4V. Then devices on both AC68U and NF4V can see each other. At the moment there are two links between AC68U and NF4V: WAN/NF4V <-> LAN/AC68U and LAN/NF4V <-> LAN/AC68U. VoIP goes from NF4V WAN to AC68U LAN. Everything else goes from NF4V LAN to AC68U LAN. From AC68U, we can access internet.