TP-Link Archer C7

Saturday, September 26, 2015

Bought one of these to get faster wi-fi, as the ISP wi-fi is only 2.4GHz 54Mbps (and rarely gets close to it). This means I can now use the ISP wi-fi as a ‘guest’ network that can’t access the other computers in the house, while the rest of us connect to the new router.

To avoid problems, I decided to use the same IP subnets on both routers. I assumed the router wouldn’t have any problem handling that, since it does NAT and both subnets are private. Oh, dear.

First time I plugged the Archer C7 into the ISP router, it went and got a DHCP address from the ISP router… and stopped working. No routing, no web page.

Turns out that it can’t handle having both WAN and LAN on overlapping subnets. Worse, when it does that, it resets its own IP address to the default 192.168.0.1, anyone using static IP configuration suddenly finds their gateway has vanished, and anyone trying to connect to the configured IP address finds it’s not there.

But it gets worse. You can’t even disconnect the WAN cable and reboot the router, because it PERMANENTLY changes the IP address back to the default. Before I realized what it was doing, I ended up resetting it to defaults and restoring the configuration backup I’d previously made (you did make a backup, right?)

Other than this peculiarity, which required me to change the IP address of pretty much every device on the LAN, and the fact that it routes private IP addresses in the first place, it seems to be working fine so far.

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