I'm entirely new to this but was able to flash the Openwrt firmware 18.06.5 onto my (new) TP-Link WDR4300 N750 v.1.7. So far so good. I have changed nothing other than setup a new password in the Web UI. To check if had any internetaccess I have pinged the router but as result I get: ping: bad address 'openwrt.org'
The router is connected to my ISP modem, with my normal router I have no problems connecting to the internet. So I'm basicly stuck already. Any help is appreciated. Thanks.
My ISP is Ziggo (dutch) and no username or password is required. I have als tried this: https://openwrt.org/docs/guide-quick-start/ts-internetconnectivity
The first 3 numbers of the WAN and LAN Ip4 addresses are in the same range, but when I try to change the LAN address I get after "Waiting for configuration to be applied" : "Failed to confirm apply within 30s, waiting for rollback..." and than nothing happens.
Maybe it is a DNS issue. Will try to change that later
I'm not sure the ISP modem behaves like a router. First I can't access the modem, secondly, it has only one ethernet port, which is connected to the WAN of my router. My other router works just fine.
Edit: I have fixed the issue.
It was a combination of things, at first I couldn't get any connection with the OpenWrt router attached to the ISP modem directly, or indirectly connected through the old router. The latter caused the problem with the same Ip4 addresses. On top of that the OpenWrt router can't ping to a domain name, when I use the IP address 126.96.36.199, instead in this case the default openwrt.org ping domain name, it works!