Failed to AddPortMapping with code 501 and other related inquiries

Got a few questions about syncing my node. I'm running Windows 11 with 16 GB of RAM and an HDD that has 707 GB free space. Using Bitcoin Core 25.0. Here's my config: 1. Every 5 minutes, I see this in the Bitcoin Core debug.log: I've set the port to 8335 since I’ve got another node on the local network using 8333. The router is set up to forward both 8333 and 8335. Do these logs mean there's an issue? 2. The syncing process is pretty slow; I'm getting a block roughly every 30 seconds. Since this node runs on an HDD, could that be affecting things? I’ve got 5 outbound connections and 1 inbound (the other node has addnode=192.168.1.100:8335). 3. I figured syncing locally should be quicker than over the internet. The peer shows a ping of 0 ms. Is there any way to give priority to the local peer? Right now, the data transfer between the two nodes is minimal (only received 3kB).

*I think* the addportmapping & deleteportmapping are both for the UPNP to your router since you said you have the static port maps it fails. How far along with the sync are you that you are only getting the 1 block per 30 seconds. The HDD will be slow but not that slow. Can you addnode=the other private IP on the .100 machine and see if both of them have the other listed in the peers. -Dave

Only 3 weeks behind now (was 6). I guess the slowness may have something to do with the number connections or the performance of the connected nodes. It's up to 8 out and (still) 1 in, and occasionally it is down to about 15 seconds per block. Also, the lack of inbound nodes is strange. I think I have the router configured correctly, but the AddPortMapping error makes me wonder. I have two local nodes, 100 and 119. Both list each other as connected peers.

That makes sense since Bitcoin Core is also listening on your LAN (or WLAN)'s local interface by default. Can you actually ping the node from the outside world though? Get the IP address you see on bitcoin-cli getnetworkinfo | jq '.localaddresses' (or just get the IPV4 address you see in the localaddresses key) and try to ping it using telnet on some far away computer not connected to your network: telnet <ip> 8333.

I was able to telnet from an outside network to port 8335.

Right, port 8335. Sorry. What happens if you try to make another node from outside connect to this network? If you don't have such a node, you can PM me the IP address and I'll try to initiate a connection from my own node. If that is successful, then I don't think that your node has a listening-for-connections problem.

The error should be relating to your UPnP setup, which should indicate that UPnP failed when trying to open the specific port. Probably just that your router isn't supporting UPnP, not too big of an issue you just need to open it yourself. The more important thing would probably to understand how your system resources are looking, how's your I/O performance, RAM usage, CPU usage when you're running Core. Since the IBD is parallelized, I don't think there would be a big benefit with synchronizing locally unless your internet is extremely slow such that it becomes a bottleneck. Something that I also realized recently is that I had no inbound peers connecting to me until I finished IBD, so that might explain your lack of inbound assuming that your port mapping is okay.

I also use HDD to store all data (with higher dbcache value), but never experience such slowness. Have you tried setting higher dbcache value? You could try replacing addnode with connect, which force it only obtain data from other local node. [1] https://bitcointalk.org/index.php?topic=5407675.0