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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),
I've seen some threads about MTU length required to be 1500 and it is. I tried changing that - it didn't work so I changed it back and it still didn't work!
Double check - from PowerShell run:
netsh interface ipv4 show subinterfaces
Example:
PS C:\> netsh interface ipv4 show subinterfaces
MTU MediaSenseState Bytes In Bytes Out Interface
---------- --------------- ------------ ------------ -------------
4294967295 1 0 14450590 Loopback Pseudo-Interface 1
1500 1 891408824 94922849 WiFi
1500 2 190977316 74523312 Ethernet
1500 5 0 0 Ethernet 2
1500 5 0 0 Local Area Connection* 1
1500 5 0 0 Local Area Connection* 2
1500 5 0 0 Bluetooth Network Connection
The reson for this behaviour: This simple IP stack does not support any PMTUD (Path MTU Discovery) .
When I try the ProSafe Discovery Tool and ProSafe Plus Utility v2.7.8, they also discover the switches but report that the admin feature is disabled on the switches.
Indeed: Following a factory reset, NSDP Configuration functions are disabled by default for security reasons.
This applies to the legacy tools only, because they are using the NSDP (Netgear Switch Discovery Protocol).
And: The current NDT (Netgear Discovery Tool) might discover switches like your GS108Ev3 (and earlier), or GS308E (very similar to your GS108Ev3) - due to lack of ressources (DRAM, Flash, ...) the modern UPnP SSDP can't be implemented on these very small switches, only by using NSDP.
I did that - and have done it again. The one labelled Main Ethernet is the LAN used for this.
C:\>netsh interface ipv4 show subinterfaces
MTU MediaSenseState Bytes In Bytes Out Interface
---------- --------------- ------------ ------------ -------------
4294967295 1 0 103549 Loopback Pseudo-Interface 1
1280 1 336594023 34626830 Tailscale
1500 5 0 0 WiFi
1500 5 0 0 Local Area Connection* 9
1500 5 0 0 Local Area Connection* 10
1500 1 3243206781 2037463622 Main Ethernet
1500 5 0 0 Bluetooth Network Connection
1500 1 41662522 312358 MGMT Ethernet
Thanks for clarifying why the admin capability is disabled.
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