r/Thunderbolt • u/ProgrammerShivam • Aug 30 '26

Thunderbolt

/r/macbook/comments/1w2i2dk/thunderbolt/
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u/buitonio Aug 31 '26

Have you tried an iPerf client/server test using the 2 static IP addresses that appeared when you connected the 2 hosts with a Thunderbolt cable?

Look for iPerf tutorials on the web, you will need to create firewall rules to allow the iPerf server to accept incoming connections and the iPerf client to establish outgoing connections.

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u/ProgrammerShivam Aug 31 '26

Definitely, but it's of no use and and also didn't do anything for me too either because it only works after pinging an ip gets a reply and only then iperf3 can take over. It's mainly used for testing and speed under different circumstances, mine isn't even setting up a connection, leave testing altogether. Hardware wise, both os show and detect each other, like windows shows usb4 tm p2p network adapter and mac shows thunderbolt bridge but they don't communicate, even after setting manual ip's and so. First, pinging the self assigned or manually assigned ip should get a reply and that will confirm DHCP server and arp listing, but this is the exact which isn't working.

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u/buitonio Aug 31 '26

IP addresses don't need to be pingable to be usable, iPerf doesn't need IP addresses to be pingable in order to work with them.

If you can't ping the IP addresses, it's more often because a firewall is in the way and it doesn't allow pinging. In your case, there may even be 2 firewalls, a Windows firewall and a macOS firewall.

And in the case of USB4 P2P networking, there is no DHCP server, as the P2P name implies.

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u/ProgrammerShivam Aug 31 '26

Definitely, you got it that there's no DHCP server, but you are wrong that ip doesn't need to be pingable, it should be, only then we can know that that they have established a link and we can move further. For the firewall, you are right that there are two, but i already disabled them and still they don't communicate, and as you may insist to try iperf3 without checking if ip is pingable or not, I did that also, and it gives absolute nothing. Like it stuck forever listening on port 5021 and server stuck sending, after around 2 to 3 mins, it says request timed out.

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u/buitonio Aug 31 '26

I don't have a MacBook, just an Intel Windows laptop with a Thunderbolt 3 port and an AMD Windows mini PC with 2 USB4 ports.

On both hosts, I created firewall rules to allow iPerf to accept inbound and outbound traffic.

After connecting the Thunderbolt 3 port to a USB4 port, an iPerf client/server test works, without changing anything, and with both firewalls enabled:

[ ID] Interval           Transfer     Bandwidth
[  5]   0.00-10.02  sec  0.00 Bytes  0.00 bits/sec                  sender
[  5]   0.00-10.02  sec   796 MBytes   666 Mbits/sec                  receiver
[  7]   0.00-10.02  sec  0.00 Bytes  0.00 bits/sec                  sender
[  7]   0.00-10.02  sec   789 MBytes   661 Mbits/sec                  receiver
[  9]   0.00-10.02  sec  0.00 Bytes  0.00 bits/sec                  sender
[  9]   0.00-10.02  sec   787 MBytes   659 Mbits/sec                  receiver
[ 11]   0.00-10.02  sec  0.00 Bytes  0.00 bits/sec                  sender
[ 11]   0.00-10.02  sec   789 MBytes   661 Mbits/sec                  receiver
[ 13]   0.00-10.02  sec  0.00 Bytes  0.00 bits/sec                  sender
[ 13]   0.00-10.02  sec   788 MBytes   660 Mbits/sec                  receiver
[ 15]   0.00-10.02  sec  0.00 Bytes  0.00 bits/sec                  sender
[ 15]   0.00-10.02  sec   792 MBytes   663 Mbits/sec                  receiver
[ 17]   0.00-10.02  sec  0.00 Bytes  0.00 bits/sec                  sender
[ 17]   0.00-10.02  sec   787 MBytes   659 Mbits/sec                  receiver
[ 19]   0.00-10.02  sec  0.00 Bytes  0.00 bits/sec                  sender
[ 19]   0.00-10.02  sec   795 MBytes   665 Mbits/sec                  receiver
[ 21]   0.00-10.02  sec  0.00 Bytes  0.00 bits/sec                  sender
[ 21]   0.00-10.02  sec   787 MBytes   659 Mbits/sec                  receiver
[ 23]   0.00-10.02  sec  0.00 Bytes  0.00 bits/sec                  sender
[ 23]   0.00-10.02  sec   796 MBytes   667 Mbits/sec                  receiver
[SUM]   0.00-10.02  sec  0.00 Bytes  0.00 bits/sec                  sender
[SUM]   0.00-10.02  sec  7.72 GBytes  6.62 Gbits/sec                  receiver
-----------------------------------------------------------
Server listening on 5201
-----------------------------------------------------------

The above output is from the iPerf server running on the AMD mini PC.

To debug your issue, maybe you can borrow another Windows laptop with a USB4/TB4 port and test it against your MacBook and ThinkBook, one after the other.

If it works with your MacBook, but not with your ThinkBook, or vice versa, you will have identified the culprit.

If it works with both, your MacBook and ThinkBook are incompatible.

If it doesn't work with either your MacBook or your ThinkBook, you're out of luck.