Now I am experiencing a strange thing...

I have a working PTP link [Dynadish] connected 5 kms apart and was working fine till Monday for past1 year.

Monday the linked dropped connectivity. On probing further I realised that the connection on one end of the network works fine when plugged into a standalone laptop.

But the same connection when plugged into the switch stops responding. There is no IP conflict.

What kind of issue is this?

link grounding?

the link was working for 2 years in the current setup and suddenly this happened. do you think grounding would do this issue?

the link was working for 2 years in the current setup and suddenly this happened. do you think grounding would do this issue?

This sounds like a spanning tree issue to me -- probably, somebody is creating a loop in the network and spanning tree is trying to block it. I would wager that something is connected to the switch that is plugged into itself and causing packets to loop. If the switch doesn't support spanning tree then the MikroTik would kick in spanning tree and block the entire switch from connecting.

I have seen customers accidentally plug switches into themselves with a long cable where both ends are nearby each other -- they see the two ends close by and assume both should be connected to the switch, and connect them, but meanwhile it is actually the same cable, so the customer has just plugged the switch into itself and created a loop. If the switch supports spanning tree, it will block this loop itself, but many unmanaged switches do not.

Unplug everything from that switch except your laptop and the dynadish. See if it works - it should. Plug the rest of the cables back in one at a time and retest so that you can figure out which connection brings everything down, and then you will find the source of the loop. There may be a switch connected directly to your switch that is plugged into itself.

when plugged in a single laptop from the Dynadish the link works perfectly. when plugged back into the switch it starts flapping...

when plugged in a single laptop from the Dynadish the link works perfectly. when plugged back into the switch it starts flapping...

And there is nothing else plugged into the switch besides the dynadish itself when you plug it back into the switch? That wasn't really clear.

so Location B now has a issue where if the cable from Dynadish is plugged directly into the laptop it can communicate and work with Location A perfectly but when the same cable is plugged into a switch ( on Location B Network ) it starts port flapping and gives the following error "Bridge port received packet with own address as source, probably loop" ( viewtopic.php?f=7&t=118150 )

so Location B now has a issue where if the cable from Dynadish is plugged directly into the laptop it can communicate and work with Location A perfectly but when the same cable is plugged into a switch ( on Location B Network ) it starts port flapping and gives the following error "Bridge port received packet with own address as source, probably loop" ( viewtopic.php?f=7&t=118150 )

OK so there is a loop, like I suspected. You need to unplug everything from the switch at location B except for the Dynadish itself. Have you done this? Do you get the loop error when the only thing plugged into the switch at location B is the dynadish? All other cables unplugged from the switch?

when the Dynadish at Location B is plugged into the switch it stops responding and this is when there is no other network cable present in the switch at that time but somehow it responds when plugged directly into the laptop.

when the Dynadish at Location B is plugged into the switch it stops responding and this is when there is no other network cable present in the switch at that time but somehow it responds when plugged directly into the laptop.

OK thank you, this is helpful. If this is the case, that nothing is plugged into the switch at location B except the dynadish and the problem still happens, then the switch at Location B may support spanning tree and may be sending out BPDU's. A loop at the other end (location A) may cause the BPDUs sent by the switch to return back the way they came, and cause the link to go down. See if the problem happens when the Dynadish at Location A is not plugged into your network. Try to just have Dynadish (Location A) <--> Dynadish (Location B) <--> Switch (Location B) without anything plugged into the switch except the Dynadish. If this does not go down, your problem is a loop at Location A, where something is plugged into itself at Location A, causing packets to loop and triggering the outage.

link grounding?

the link was working for 2 years in the current setup and suddenly this happened. do you think grounding would do this issue?

so the cable was the culprit.

i installed 3 different Mikrotik devices at the tower end of the cable and was facing the same problem and that made me zoom in on the problem.

the cable length is 65 meters.

change the cable finally!!!