LAN access but no internet connection unless different subnet [closed]

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LAN access but no internet connection unless different subnet [closed] – Managing your servers can streamline the performance of your team by allowing them to complete complex tasks faster. Plus, it can enable them to detect problems early on before they get out of hand and compromise your business. As a result, the risk of experiencing operational setbacks is drastically lower.

But the only way to make the most of your server management is to perform it correctly. And to help you do so, this article will share nine tips on improving your server management and fix some problem about linux, routing, internet, subnet, access-point.

Dear SF@StackExchange,

I’m using an access point that provides LAN as well as WLAN capabilities using 4G to connect its hosts to the internet. DHCP is deactivated by design. Regardless of the OS connected, I can ping across WLAN -> LAN, LAN -> LAN and whatnot. Windows PC’s are not affected of this and connect to the internet just fine leading me to believe it is within the settings of my Linux box I need to look.

When I’m on my Linux box however, I cannot get WLAN internet access while the WLAN interface on the AP shares the same subnet (255.255.0.0) as the LAN.

For instance, I cannot connect to the internet when both share the IP address space 169.254.x.x but I can get connectivity through this setup:

WLAN: Default GW: 192.168.1.1, Subnet: 255.255.255.0

LAN: Default GW: 169.254.2.1, Subnet: 255.255.0.0

which is not what I’d like since that messes up the port forwarding that I will need.

I’ve tried setting up DNS for my linux machine as 8.8.8.8. It can still ping the AP when sharing the same subnet at 169.254.2.1.

Route -n log:

Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         169.254.2.1     0.0.0.0         UG    600    0        0 wlp3s0
169.254.0.0     0.0.0.0         255.255.0.0     U     600    0        0 wlp3s0

cat /etc/resolv.conf:

# Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)
#     DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN
nameserver 127.0.1.1

(It does state this with a working AP too though)

Solution :

The combination of your environment and mess in your head is too complex to give a straight answer. First of all, 169.254/16 is Windows autoconfiguration prefix that is used when no DHCP server is reachable and Windows IP stack is configured to use DHCP. Linux by default doesn’t have this feature enabled, so that’s why you cannot get the outer world connectivity. Second, clearly there’s a static subnet configured on your AP, and it’s 192.168.1.0/24 – seems like access point default settings are in effect.

Conclusion: scratch out your experiment result as irrelevant, get a DHCP server or use static IPs. Your design, which made your DHCP disabled is completely wrong.

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