Just spend some hours hunting down ghosts, and wanted to help anyone having the same issue as me:
I created a NFS share on a Synology NAS, mounted it to the PVE and run a backup. All fine so far. After some days it dropped offline. For good.
I did all the tests,
ping works,
nmap as well:
but
So the solution for this beauty is to disable in the Synology NAS under networking "Reply to ARP requests if the target IP address is a local address configured on the incoming interface"
Luckily I found this tread, just created a streamlined version since it took me almost two hours for finding it - maybe you are quicker
https://forum.proxmox.com/threads/mount-no-longer-works-in-proxmox-6-nfs-synology.56503/post-263048
I created a NFS share on a Synology NAS, mounted it to the PVE and run a backup. All fine so far. After some days it dropped offline. For good.
I did all the tests,
ping works,
nmap as well:
user@host:~# nmap -p 111,2049 10.0.0.1
Starting Nmap 7.93 ( https://nmap.org ) at 2025-05-17 23:34 CEST
Nmap scan report for 10.0.0.1
Host is up (0.00057s latency).
PORT STATE SERVICE
111/tcp open rpcbind
2049/tcp open nfs
MAC Address: 90:091:44:33:8C (Synology Incorporated)
Nmap done: 1 IP address (1 host up) scanned in 0.11 seconds
but
So the solution for this beauty is to disable in the Synology NAS under networking "Reply to ARP requests if the target IP address is a local address configured on the incoming interface"
Luckily I found this tread, just created a streamlined version since it took me almost two hours for finding it - maybe you are quicker
https://forum.proxmox.com/threads/mount-no-longer-works-in-proxmox-6-nfs-synology.56503/post-263048
