I just found a strange network routing problem with my Manjaro box.
I am running my home network behind a Fritz!Box, which does all the routing and the internet connection. This Fritz!Box also establishes a VPN connection to my Mom’s home. The weird matter of the fact is, that I cannot connect to my Mom’s network from my Manjaro system. It however works from my Raspberry Pi4 running pihole as the local nameserver. No static routes (IPv4 or IPv6) or other settings, which could impact the routing, are active on the Fritz!Box.
Local network:
address 192.168.178.0/24
local ip4 192.168.178.46 (troja, Manjaro Linux)
nameserver 192.168.178.5 (pihole, Raspberry Pi OS)
fritzbox 192.168.178.1
Remote network:
address 192.168.200.0/24
fritzbox 192.168.200.1
Doing a nslookup
of the remote Fritz!Box gives the absolutely same response an both machines:
[stefan@troja ~]$ nslookup fritzfn
Server: 192.168.178.5
Address: 192.168.178.5#53
Name: fritzfn.fritz.box
Address: 192.168.200.1
[stefan@troja ~]$ ssh pihole nslookup fritzfn
Server: 192.168.178.5
Address: 192.168.178.5#53
Name: fritzfn.fritz.box
Address: 192.168.200.1
Trying to ping
the remote Fritz!Box fritzfn from both systems looks like this:
[stefan@troja ~]$ ping fritzfn
PING fritzfn.fritz.box (192.168.200.1) 56(84) bytes of data.
From p3e9bf2ae.dip0.t-ipconnect.de (62.155.242.174) icmp_seq=1 Destination Net Unreachable
From p3e9bf2ae.dip0.t-ipconnect.de (62.155.242.174) icmp_seq=2 Destination Net Unreachable
From p3e9bf2ae.dip0.t-ipconnect.de (62.155.242.174) icmp_seq=3 Destination Net Unreachable
From p3e9bf2ae.dip0.t-ipconnect.de (62.155.242.174) icmp_seq=4 Destination Net Unreachable
--- fritzfn.fritz.box ping statistics ---
4 packets transmitted, 0 received, +4 errors, 100% packet loss, time 3004ms
[stefan@troja ~]$ ssh pihole ping fritzfn
PING fritzfn.fritz.box (192.168.200.1) 56(84) bytes of data.
64 bytes from fritzfn.fritz.box (192.168.200.1): icmp_seq=1 ttl=63 time=48.3 ms
64 bytes from fritzfn.fritz.box (192.168.200.1): icmp_seq=2 ttl=63 time=34.6 ms
64 bytes from fritzfn.fritz.box (192.168.200.1): icmp_seq=3 ttl=63 time=36.8 ms
The routing tables on both machines indicate, that traffic to 192.168.200.x
should be routed via the default route:
[stefan@troja ~]$ ip route show
default via 192.168.178.1 dev eno1 proto dhcp metric 100
10.10.10.0/24 dev cni-podman0 proto kernel scope link src 10.10.10.1
10.88.2.0/24 dev cni-podman2 proto kernel scope link src 10.88.2.1 linkdown
192.168.122.0/24 dev virbr0 proto kernel scope link src 192.168.122.1 linkdown
192.168.178.0/24 dev eno1 proto kernel scope link src 192.168.178.46 metric 100
192.168.222.0/24 dev virbr1 proto kernel scope link src 192.168.222.1 linkdown
[stefan@troja ~]$ ssh pihole ip route show
default via 192.168.178.1 dev eth0 proto dhcp src 192.168.178.5 metric 202
172.22.0.0/24 dev wg0 proto kernel scope link src 172.22.0.1
192.168.178.0/24 dev eth0 proto dhcp scope link src 192.168.178.5 metric 202
Now the question, why is traffic routing to the remote network 192.168.200.x
different depending on the initiating host?
The problem is independent from the network interface. It exists when connected to my router via Ethernet or WiFi.