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Solved
GS108Ev3 refuses to connect
I have 4 GS108Ev3 switches. As they are all configured and working well I don't need to administer them often. Today I wanted to login to them - and can't. All 4 refuse to connect when I acces...
Here what Tailscale says about such issues:
Packet size limits can also cause connection problems on certain types of networks.
Tailscale uses a maximum transmission unit (MTU) of 1280. If there are other interfaces which might send a packet larger than this, those packets might get dropped silently. These can be verified by using tcpdump.
The limitation in your use case isn't (only) Tailscale.
It's much more the very simple IP stack "glued on" to the GS108Ev3, and many more Plus resp. Easy Smart switches not built in a real managed switch core, therefore not supporting PMTUD (Path MTU DIscovery), and not allowing MTU smaller but the default 1500.The ubiquitous ICMP Ping check not allowing fragmentation does show the effective path MTU limit
PS C:\> ping 10.10.1.176 -f -l 1472
Pinging 10.10.1.176 with 1472 bytes of data:
Reply from 10.10.1.176: bytes=1472 time=8ms TTL=64
Reply from 10.10.1.176: bytes=1472 time=2ms TTL=64
Reply from 10.10.1.176: bytes=1472 time=3ms TTL=64
Reply from 10.10.1.176: bytes=1472 time=3ms TTL=64
Ping statistics for 10.10.1.176:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 2ms, Maximum = 8ms, Average = 4ms
But beyond:
PS C:\> ping 10.10.1.176 -f -l 1473
Pinging 10.10.1.176 with 1473 bytes of data:
Packet needs to be fragmented but DF set.
Packet needs to be fragmented but DF set.
Packet needs to be fragmented but DF set.
Packet needs to be fragmented but DF set.
Ping statistics for 10.10.1.176:
Packets: Sent = 4, Received = 0, Lost = 4 (100% loss),
OK, I have figured out what is causing it and can work around it - but don't understand why yet!
This PC rune Tailscale. When that is enabled then I can't access those admin pages despite them being on the same LAN and main switch. When I exit Tailscale, I can.
I can live with this and will try to figure out what is causing it!
Even with that, one provided the admin login screen but did nothing when a password was entered. I had to factory reset it, after removing it's reserved DHCP lease so it assumed a new IP address. Only then would it properly factory reset and allow login and administration.
At least they are working but clearly I need to delve deeper into what is happening!
Here what Tailscale says about such issues:
Packet size limits can also cause connection problems on certain types of networks.
Tailscale uses a maximum transmission unit (MTU) of 1280. If there are other interfaces which might send a packet larger than this, those packets might get dropped silently. These can be verified by using tcpdump.
The limitation in your use case isn't (only) Tailscale.
It's much more the very simple IP stack "glued on" to the GS108Ev3, and many more Plus resp. Easy Smart switches not built in a real managed switch core, therefore not supporting PMTUD (Path MTU DIscovery), and not allowing MTU smaller but the default 1500.
The ubiquitous ICMP Ping check not allowing fragmentation does show the effective path MTU limit
PS C:\> ping 10.10.1.176 -f -l 1472
Pinging 10.10.1.176 with 1472 bytes of data:
Reply from 10.10.1.176: bytes=1472 time=8ms TTL=64
Reply from 10.10.1.176: bytes=1472 time=2ms TTL=64
Reply from 10.10.1.176: bytes=1472 time=3ms TTL=64
Reply from 10.10.1.176: bytes=1472 time=3ms TTL=64
Ping statistics for 10.10.1.176:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 2ms, Maximum = 8ms, Average = 4ms
But beyond:
PS C:\> ping 10.10.1.176 -f -l 1473
Pinging 10.10.1.176 with 1473 bytes of data:
Packet needs to be fragmented but DF set.
Packet needs to be fragmented but DF set.
Packet needs to be fragmented but DF set.
Packet needs to be fragmented but DF set.
Ping statistics for 10.10.1.176:
Packets: Sent = 4, Received = 0, Lost = 4 (100% loss),
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