I have a Synology NAS at home (let's call it ananas), it is attached to my router via ethernet.
I also have a desktop (let's call it Aero), it is connected to the same router via wifi.
I configured in another country, a laptop (xps13), I could access the NAS without any problem (the ports were open and I used NAT) using https rsync over ssh and ssh.
However now that I am back home, I just can't find the NAS by using nmap (without
-Pn, it is just not listed while everything else is), can't ping it, and can't ssh into it. The twist is that this only happens on the laptop.
route -n on the xps 13 yields:
[soulthym@xps13 ~]$ route -n Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 0.0.0.0 192.168.1.1 0.0.0.0 UG 600 0 0 wlp2s0 192.168.1.0 0.0.0.0 255.255.255.0 U 600 0 0 wlp2s0
And on the Aero:
[soulthym@Aero ~]$ route -n Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 0.0.0.0 192.168.1.1 0.0.0.0 UG 303 0 0 wlp3s0 192.168.1.0 0.0.0.0 255.255.255.0 U 303 0 0 wlp3s0 192.168.1.0 0.0.0.0 255.255.255.0 U 600 0 0 wlp3s0
For debugging purposes I disabled the firewall on the NAS, disabled IP auto-blocking on the NAS, and set the exact same firewall on both the Desktop and the Laptop (using /etc/iptables/iptables.rules).
From the xps13 I get:
[soulthym@xps13 ~]$ nmap -Pn 192.168.1.17 Starting Nmap 7.70 ( https://nmap.org ) at 2019-08-19 18:22 CEST Nmap scan report for ananas-1.home (192.168.1.17) Host is up (0.16s latency). All 1000 scanned ports on ananas-1.home (192.168.1.17) are filtered Nmap done: 1 IP address (1 host up) scanned in 8.88 seconds
Whereas I get all the ports from the Aero.
Same story goes for pinging, works beautifully from the Aero, but the xps13 yields:
[soulthym@xps13 ~]$ ping 192.168.1.17 PING 192.168.1.17 (192.168.1.17) 56(84) bytes of data. From 192.168.1.13 icmp_seq=1 Destination Host Unreachable From 192.168.1.13 icmp_seq=2 Destination Host Unreachable From 192.168.1.13 icmp_seq=3 Destination Host Unreachable
And while ssh-ing:
ssh: connect to host 192.168.1.17 port $PORT: No route to host
[soulthym@xps13 ~]$ ip neigh 192.168.1.1 dev wlp2s0 lladdr xx:xx:xx:xx:xx:xx REACHABLE 192.168.1.10 dev wlp2s0 lladdr xx:xx:xx:xx:xx:xx STALE 192.168.1.17 dev wlp2s0 FAILED xxxx::xxxx:xxxx:xxxx:xxxx dev wlp2s0 lladdr xx:xx:xx:xx:xx:xx router REACHABLE
(the above fragment was moved from a comment, and was broken there)
This only happens when using the local network. I can use a VPN and connect to the public IP but that is just a temporary fix that doesn't fit the use for backups...
Any idea of what I could have done wrong here?