Default Gateway not working in Routed Network with Static IP's unless myDns used

Projects Networking, Protocols, and Devices
1

Hello Forum,

This is my first query, so please be kind.

I have an issue when trying to connect to devices behind different networks.
This is not a home NAT'd setup. Two or more different networks connected with routers and default gateways.

The first sketch doesn't work. The IP settings don't establish a route/arp table when checking with Wireshark.
If the exact same settings however are requested and received from DHCP, all is OK.

The second sketch works. The addition of myDns solves the issue. It doesn't matter what i set the DNS IP address to, it just needs it. My project however doesn't required any DNS services.
After adding this is can see the route/arp requests exchange in Wireshark and the connection establishes.

What is myDns doing in the back ground to correct this action?

When using DHCP and not declaring myDns the sketch will still work. So I'm assuming that the data is still being collected in the library's inner workings.

Is there something wrong here?

Cheers,

Oondyba

routing_issue_not_working.ino (925 Bytes)

routing_issue_working.ino (998 Bytes)

2

This sounds like something I ran into quite a few years ago (so it is just a bit fuzzy in my head), but what I found was that DHCP was handing out some other piece of information that I had not expected and that was what was keeping everything happy. For the life of me, I can't remember exactly what it was, but with wireshark, you should be able to see what other "goodies" are being handed out by DHCP. Sorry I can't be more specific.