Problem with connecting the W5500 chip to the internet via a router

Question

Good day everybody, I have connected my W5500 module to a router with an ethernet cable, and I want to send TCP and UDP packets over the network. Sending packets to local nodes on the same network works fine, but when I try to send a packet to an external network, the chip will send an ARP request for the external address a number of times, then timeouts. image1087×158 9.99 KB Which is understandable, because as far as I know ARP is meant to get the hardware address of the local nodes, and since no node with that specific IP address exists on the immediate network, no one will respond to it. In my case, the packet needs to arrive at the router, and then let the router decide where it should go next. But if I set the DIPR0 to DIPR4 register to the IP address of a node in an external network, it will send a fruitless ARP request as I described above. My question is, how can I achieve this with the W5500 chip? Looking into the datasheet, I found that the GAR0 to GAR4 registers are supposed to hold the Gateway address, but there’s literally zero mentions of Gateways in the datasheet or the online wiki. How can I tell the W5500 chip to send these types of packets to the router instead of trying to ARP for the external address and fail? Thanks for your time

Eugeny · Answer

Let’s start with MAC address - yours starts with 0xde, which is “locally administered”, see here. Not sure how W5500 treats it exactly, but it would be the first thing to change. Then you must configure gateway IP address in the GAR, and if remote address is outside of the current network (defined by SIP and mask) packets will be routed to the gateway.