I'm getting weird results on a GL-A1300 in router mode running firmware 4.5.19 with the WAN port hardwired to an ISP router. When a client connects to the GL 2.4 GHz WiFI network, it receives a DHCP address from the upstream (ISP) router. [The 2.4 GHz WiFi on the upstream router is off, and even if on it would have a different name.] Connecting to the 5 GHz GL network does not have this problem. I also ran into the reverse situation where a device requesting an IP address on the upstream WAN hard-wired network (which is behind the ISP router), received a DHCP address from the GL router. My guess is that DHCP requests and responses are being forwarded across the GL's WAN interface in both directions, which seems incorrect to me. Looks like I can't upload a PNG diagram, so here's an attempt with ASCII. I've experimented with this multiple ways/times and this is indeed happening the way I described.
Thanks, but that setting was and still is disabled. Incidentally, my ISP router is an Xfinity Xfi and I would gladly disable DHCP on it, but that does not appear to be an option. Also, I saw an older post discussing special treatment when the WAN network is in private space. I wonder if that only applies for 192.168 (i.e., what about 10.0 or 172.16-31?). I'm hoping someone from GL will test this with the exact network ranges I cited in the original post and will hopefully reproduce it.
I realize the IP ranges SHOULD not matter, but I what I'm observing is possibly a bug and in this case, the network ranges might alter the buggy behavior. I suspect repeating this exact scenario will repro the issue. The WAN port is configured as a WAN port, and the GL router obtains a 192.168.14 IP address from the ISP DHCP server. The GL router is connected to the ISP router via a single Ethernet cable, and that is the only connection on the ISP router. Also, this only happens across the 2.4 GHZ network of the GL and not the 5 GHz (reminder, 2.4 GHz is disabled on the ISP router). The logical explanation for what I am observing is that DHCP packets are being forwarded across the WAN port of the GL router, which is kind of surprising given that the request is coming across the WiFI side. FWIW, sometimes, the requesting device gets a DHCP address from the GL router, but other times, it gets a DHCP address from the ISP router.
The issue might be the guest network - this guest network is (always? @alzhao) your LAN network +1 in default. So if you use 192.168.13.x for your LAN on the GL, the guest network might be 192.168.14.x by default then - which would be the same like the upstream network.
Well, my guest network is set to 192.168.9.0/24. Also, both 2.4 and 5 GHz guest WiFI networks are disabled. Even if I had screwed up and the guest network was 14, connecting to the non-guest 2.4 should still have given me an IP on the '13' subnet. Oh, one more thing -- when I get a '14' IP address via DHCP, I show up in the list of clients on the ISP router, and of course not on the GL router.
Is anyone with GL trying to research this? FYI, I'm a network guy who has worked with TCP/IP and Ethernet for over 25 years. I am telling you that clients connecting to the GL 2.4 GHz network are (sometimes) getting IP addresses via DHCP from the upstream ISP router, which is a significant bug as I see it. I have several 2.4 GHz devices that need to be behind the GL but that cannot set their own IPs manually, so turning off DHCP on the GL is not an option.
Can you give detailed steps to replicate this? Theoretically should not happen if you use the default config.
Did you ever change config e.g. doing some bridging?
Can you give me the log and configure of the router? You can ssh to the router and give me the content of /etc/config/network /etc/config/wireless /etc/config/firewall
