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Today's Topics:

    1. LAN connectivity problem (Graeme Gemmill)
    2. Re: LAN connectivity problem (Tim)


Message: 1
Date: Sun, 23 Jan 2022 15:21:11 +0000
From: Graeme Gemmill <gra...@gemmill.name>
To: dorset@mailman.lug.org.uk
Subject: [Dorset] LAN connectivity problem
Message-ID: <1f39da2a-df73-7f82-fd63-d17e4dc05...@gemmill.name>
Content-Type: text/plain; charset=UTF-8; format=flowed

I would be grateful for suggestions to solve the following connection
In the following description, D stands for 192.168.1
My router, D.1, has a control panel that identifies the following
ethernet connected devices: ? f0:2f:74:1f:d0:99??? ?? y b8:27:eb:50:44:91??? y ?? f4:30:b9:83:84:1c???? y ?? 74:03:bd:0c:b0:38??? y ?? 40:16:7e:b4:09:e2??? y

y indicates that the device passes traffic to the WAN

My laptop, D.3 shown the following devices by ip neigh: enp1s0??? c4:ea:1d:e4:27:a2??? REACHABLE??? ? Y enp1s0??? f0:2f:74:1f:d0:99?????? STALE ??? N enp1s0??? 74:03:bd:0c:b0:38??? STALE N enp1s0??? 40:16:7e:b4:09:e2??? STALE N

Y/N indicates ping success.
D.3 "knows about" D.6, D.9 and D.10 because they are in /etc/fstab as a
result of previously successful connections.

D.9 acts as a server and shows the following by ip neigh: ??? enp2s0??? c4:ea:1d:e4:27:a2?? REACHABLE??? Y ?? ? enp2s0??? f0:2f:74:1f:d0:99????? REACHABLE??? Y ? enp2s0??? b8:27:eb:50:44:91 STALE?????????????? Y ??? enp2s0??? 74:03:bd:0c:b0:38 STALE?????????????? Y

D.10 is my main work PC, and shows the following via ip neigh: ??? enp5s0??? c4:ea:1d:e4:27:a2??? REACHABLE??? Y ? enp5s0??? b8:27:eb:50:44:91??? REACHABLE??? Y ??? ?? enp5s0??? 74:03:bd:0c:b0:38??? STALE ??? Y ??? enp5s0??? 40:16:7e:b4:09:e2??? REACHABLE??? Y

D.6 ia a NAS box that both D.9 and D.10 can and do write to.
D.6, D.9, D.10 and D.16 are connected to D.1 via an 8-way Netgear hub
My problem: D.3 cannot reach D.9 or D.10, and neither D.9 nor D.10 can
reach D.3, despite all being connected to D.1
(I hope the attempt at tabulating this data survives the translation to
other mail clients)

Hi Tim. All IP addresses are static. Connection is ethernet in all cases, transport by powerline adaptors. ifconfig outputsĀ  for D.3, D.9 and D.10 are consistent. Firewall is off on all three until this is resolved.
nmap reports:
#nmap -O
Starting Nmap 7.91 ( https://nmap.org ) at 2022-01-24 12:56 GMT
Note: Host seems down. If it is really up, but blocking our ping probes, try -Pn

Looked up ping blocking, but /proc/sys/net/ipv4/icmp_echo_ignore_all is 0, so something else is blocking pings.
Reset of router and switch performed to no avail.

Running Wireshark on D.10, capturing packets to/from D.3
All frames say "Who has Tell" (mostly)
So looking forward to further enlightenment!

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