Hi @juergenurban 

Thanks for posting in our business forum.

The provided information is not enough to judge if it is a problem with the device. What do you mean "in different networks and switches"?

You probably should consider what happened to your network environment or the setup. If something is not correct, ACL or VLAN can stop that from accessing.

Or you can set up a static IP to match the default VLAN 1 IP address on a port that is untagged with PVID 1 and try again your telnet command.

  @Clive_A There are two networks which cannot talk to each other (because of firewall), but it is possible to connect from outside network to both networks.

The following diagrams show the two networks:

Network 1:

Network 2:

Telnet on sw2 and switch1 are failing sometimes.

ACL is not used.

VLAN ID 1 is already used to access the switches. The switches have a fixed IP address. It is still possible to reach the switch via http interface which I interpret as that the VLAN is working correctly.

It is not easily possible to see what happens before as a script is accessing the telnet ports and is doing something which I currently do not know.

Hi @juergenurban 

Thanks for posting in our business forum.

juergenurban wrote

  @Clive_A There are two networks which cannot talk to each other (because of firewall), but it is possible to connect from outside network to both networks.

The following diagrams show the two networks:

Network 1:

 

 

Network 2:

 

Telnet on sw2 and switch1 are failing sometimes.

ACL is not used.

VLAN ID 1 is already used to access the switches. The switches have a fixed IP address. It is still possible to reach the switch via http interface which I interpret as that the VLAN is working correctly.

It is not easily possible to see what happens before as a script is accessing the telnet ports and is doing something which I currently do not know.

Screenshots of your diagram look fine to me.

When you fail to telnet, can you please Wireshark and find out what's wrong with the connection?

If possible, paste the screenshots here after you filtered it.

I can try to use wireshark when it is failing, but what I remember there is normally so much traffic that it is really difficult. There are sometimes testsuites running which are testing the worst case conditions for network transfers.

The telnet problems actually occured with software version 1.20.0 for TL-SG3452. After selecting the backup firmware 1.0.0, the problem did not yet occured with that switch. The software version 1.0.0 from the Boot Config is somehow displayed as 1.1.4 when used. Were there changes in telnet CLI between 1.0.0 and 1.20.0? I know that the name of the switch changed. The script had problems with 1.20.0 which could also be caused by changes in white space.

Were there similar changes for TL-SG3428? e.g. between software version 1.1.8 and 1.1.1.

Hi  @juergenurban

juergenurban wrote

I can try to use wireshark when it is failing, but what I remember there is normally so much traffic that it is really difficult. There are sometimes testsuites running which are testing the worst case conditions for network transfers.

 

The telnet problems actually occured with software version 1.20.0 for TL-SG3452. After selecting the backup firmware 1.0.0, the problem did not yet occured with that switch. The software version 1.0.0 from the Boot Config is somehow displayed as 1.1.4 when used. Were there changes in telnet CLI between 1.0.0 and 1.20.0? I know that the name of the switch changed. The script had problems with 1.20.0 which could also be caused by changes in white space.

 

Were there similar changes for TL-SG3428? e.g. between software version 1.1.8 and 1.1.1.

No. Look, the telnel uses a specific port. It would not be hard if you filter the traffic which Wireshark encourages you do so.

With the 1.0.0 backup, you can telnet in the switch but were there any changes since the 1.0.0? That would be a very long time since 1.0.0 to 1.1.4 firmware.

Please do not involve the hardware version here. We have an announcement for the hardware change please go and refer to that article. In short, it is not an issue with the hardware.

My point would still be if you have a change on your config.