IP-telegram-hops

[Trond Hoyem]

I am not sure if this is the right forum, but I guess someone might be able to help anyway.

I have in a large project some problems with telegrams sent from SpaceLYnk. In this project we have 30 distribution boards, all equiped with one SL and a number og IP-routers that work as Line Couplers. 

There is an override function that we need for all heating actuators that needs to be sent to every line in the project. If we connect the PC to a line and send the telegram from ETS, we can see that the telegram is forwarded on all lines. But if we go to the object list in a SL the telegram is only forwarded to the lines in the same distribution board as the SL is installed.

I have discussed this problem with someone from Schneider, and we were thinking maybe there is a difference in the multicast telegram sent from SL compared to when we send it from the ETS. Is there in some way defined how many switches a multicast telegram from SL kan be sent thru? If so, what is the number, and more importantly; can this be changed?

As it is now, to send a telegram from one distribution board to another, the telegram needs to pass thru 5 network switches.

Simplyfied network plan with only two DB's is attached to the post.

[admin]

Try increasing Multicast TTL value in KNX connection settings in System config.

[Trond Hoyem]

Try increasing Multicast TTL value in KNX connection settings in System config.

That did not help. In the manual it is stated that this parameter has do do with communication between different sub-networks, but that is not really what we are doing here.

[admin]

Then maybe some additional switch configuration is required. You can use also run Wireshark to check what is the difference in multicast packets compared to ETS.

[Trond Hoyem]

Then maybe some additional switch configuration is required. You can use also run Wireshark to check what is the difference in multicast packets compared to ETS.

OK, this is now working. I tried to set TTL to 5, as that is the number of switches according to our info. That did not work, but by raising it to 16, as is the same value as the IP-routers has, then it works.

Thx for help!

[Tokatubs]

Having a similar experience. Have lots of ip routers on different subnets. IT department says subnets are open and multicast is on.
Have problem with traffic. Tried now to put a larger number on TTL and then the telegrams starter coming. But only read. Not possible to write.

Is there a formula on the TTL setting or is it just testing to find right number.

[admin]

+1 TTL for each router that the telegram has to pass