@tesparza said in Multicast sometimes fast sometimes extremely slow:
They all have 1 GIG uplink
Are you absolutely sure? It needs just one slow PC out of 30 in a multicast session to cause the whole lot to be very slow. Have you checked all link speed LEDs on the clients?
Possibly on one of the clients a hard disk is going to die soon and is making the whole machine and therefor the multicast session slow.
It’s impossible for us to diagnose this as we don’t have access to your (network) setup and debug this. You need to do tests to find if some of the machines are making more issues than others. Split the group of 30 into batches of 5 PCs and multicast to those. Try every batch at least three times in a row and note down all the speeds and times. When you find one 5er batch to be slow take out lets say number one and test on 2, 3, 4 and 5. Again slow? Then multicast to 1, 3, 4 and 5. This way you should be able to figure out which PC(s) exactly are causing the slowness.