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Thunderbolt Networking Setup

Thunderbolt Networking

this gist is part of this series

you wil need proxmox kernel 6.2.16-14-pve or higher.

Load Kernel Modules

  • add thunderbolt and thunderbolt-net kernel modules (this must be done all nodes - yes i know it can sometimes work withoutm but the thuderbolt-net one has interesting behaviou' so do as i say - add both ;-)
    1. nano /etc/modules add modules at bottom of file, one on each line
    2. save using x then y then enter

Prepare /etc/network/interfaces

doing this means we don't have to give each thunderbolt a manual IPv6 addrees and that these addresses stay constant no matter what Add the following to each node using nano /etc/network/interfaces

If you see any sections called thunderbolt0 or thunderbol1 delete them at this point.

Create entries to prepopulate gui with reminder

Doing this means we don't have to give each thunderbolt a manual IPv6 or IPv4 addrees and that these addresses stay constant no matter what.

Add the following to each node using nano /etc/network/interfaces this to remind you not to edit en05 and en06 in the GUI

This fragment should go between the existing auto lo section and adapater sections.

iface en05 inet manual
#do not edit it GUI

iface en06 inet manual
#do not edit in GUI

If you see any thunderbol sections delete them from the file before you save it.

*DO NOT DELETE the source /etc/network/interfaces.d/* this will always exist on the latest versions and should be the last or next to last line in /interfaces file

Rename Thunderbolt Connections

This is needed as proxmox doesn't recognize the thunderbolt interface name. There are various methods to do this. This method was selected after trial and error because:

  • the thunderboltX naming is not fixed to a port (it seems to be based on sequence you plug the cables in)
  • the MAC address of the interfaces changes with most cable insertion and removale events
  1. use udevadm monitor command to find your device IDs when you insert and remove each TB4 cable. Yes you can use other ways to do this, i recommend this one as it is great way to understand what udev does - the command proved more useful to me than the syslog or lspci command for troublehsooting thunderbolt issues and behavious. In my case my two pci paths are 0000:00:0d.2and 0000:00:0d.3 if you bought the same hardware this will be the same on all 3 units. Don't assume your PCI device paths will be the same as mine.

  2. create a link file using nano /etc/systemd/network/00-thunderbolt0.link and enter the following content:

[Match]
Path=pci-0000:00:0d.2
Driver=thunderbolt-net
[Link]
MACAddressPolicy=none
Name=en05
  1. create a second link file using nano /etc/systemd/network/00-thunderbolt1.link and enter the following content:
[Match]
Path=pci-0000:00:0d.3
Driver=thunderbolt-net
[Link]
MACAddressPolicy=none
Name=en06

Set Interfaces to UP on reboots and cable insertions

This section en sure that the interfaces will be brought up at boot or cable insertion with whatever settings are in /etc/network/interfaces - this shouldn't need to be done, it seems like a bug in the way thunderbolt networking is handled (i assume this is debian wide but haven't checked).

Huge thanks to @corvy for figuring out a script that should make this much much more reliable for most

  1. create a udev rule to detect for cable insertion using nano /etc/udev/rules.d/10-tb-en.rules with the following content:
ACTION=="move", SUBSYSTEM=="net", KERNEL=="en05", RUN+="/usr/local/bin/pve-en05.sh"
ACTION=="move", SUBSYSTEM=="net", KERNEL=="en06", RUN+="/usr/local/bin/pve-en06.sh"
  1. save the file

  2. create the first script referenced above using nano /usr/local/bin/pve-en05.sh and with the follwing content:

#!/bin/bash

LOGFILE="/tmp/udev-debug.log"
VERBOSE="" # Set this to "-v" for verbose logging
IF="en05"

echo "$(date): pve-$IF.sh triggered by udev" >> "$LOGFILE"

# If multiple interfaces go up at the same time, 
# retry 10 times and break the retry when successful
for i in {1..10}; do
    echo "$(date): Attempt $i to bring up $IF" >> "$LOGFILE"
    /usr/sbin/ifup $VERBOSE $IF >> "$LOGFILE" 2>&1 && {
        echo "$(date): Successfully brought up $IF on attempt $i" >> "$LOGFILE"
        break
    }
  
    echo "$(date): Attempt $i failed, retrying in 3 seconds..." >> "$LOGFILE"
    sleep 3
done

save the file and then

  1. create the second script referenced above using nano /usr/local/bin/pve-en06.sh and with the follwing content:
#!/bin/bash

LOGFILE="/tmp/udev-debug.log"
VERBOSE="" # Set this to "-v" for verbose logging
IF="en06"

echo "$(date): pve-$IF.sh triggered by udev" >> "$LOGFILE"

# If multiple interfaces go up at the same time, 
# retry 10 times and break the retry when successful
for i in {1..10}; do
    echo "$(date): Attempt $i to bring up $IF" >> "$LOGFILE"
    /usr/sbin/ifup $VERBOSE $IF >> "$LOGFILE" 2>&1 && {
        echo "$(date): Successfully brought up $IF on attempt $i" >> "$LOGFILE"
        break
    }
  
    echo "$(date): Attempt $i failed, retrying in 3 seconds..." >> "$LOGFILE"
    sleep 3
done

and save the file

  1. make both scripts executable with chmod +x /usr/local/bin/*.sh
  2. run update-initramfs -u -k all to propogate the new link files into initramfs
  3. Reboot (restarting networking, init 1 and init 3 are not good enough, so reboot)

Enabling IP Connectivity

proceed to the next gist

Slow Thunderbolt Performance? Too Many Retries? No traffic? Try this!

verify neighbors can see each other (connectivity troubleshooting)

##3 Install LLDP - this is great to see what nodes can see which.

  • install lldpctl with apt install lldpd on all 3 nodes
  • execute lldpctl you should info

make sure iommu is enabled (speed troubleshooting)

if you are having speed issues make sure the following is set on the kernel command line in /etc/default/grub file intel_iommu=on iommu=pt one set be sure to run update-grub and reboot

everyones grub command line is different this is mine because i also have i915 virtualization, if you get this wrong you can break your machine, if you are not doing that you don't need the i915 entries you see below

GRUB_CMDLINE_LINUX_DEFAULT="quiet intel_iommu=on iommu=pt" (note if you have more things in your cmd line DO NOT REMOVE them, just add the two intel ones, doesnt matter where.

Pinning the Thunderbolt Driver (speed and retries troubleshooting)

identify you P and E cores by running the following

cat /sys/devices/cpu_core/cpus && cat /sys/devices/cpu_atom/cpus

you should get two lines on an intel system with P and E cores. first line should be your P cores second line should be your E cores

for example on mine:

root@pve1:/etc/pve# cat /sys/devices/cpu_core/cpus && cat /sys/devices/cpu_atom/cpus
0-7
8-15

create a script to apply affinity settings everytime a thunderbolt interface comes up

  1. make a file at /etc/network/if-up.d/thunderbolt-affinity
  2. add the following to it - make sure to replace echo X-Y with whatever the report told you were your performance cores - e.g. echo 0-7
#!/bin/bash

# Check if the interface is either en05 or en06
if [ "$IFACE" = "en05" ] || [ "$IFACE" = "en06" ]; then
# Set Thunderbot affinity to Pcores
    grep thunderbolt /proc/interrupts | cut -d ":" -f1 | xargs -I {} sh -c 'echo X-Y | tee "/proc/irq/{}/smp_affinity_list"'
fi
  1. save the file - done

Extra Debugging for Thunderbolt

dynamic kernel tracing - adds more info to dmesg, doesn't overhwelm dmesg

I have only tried this on 6.8 kernels, so YMMV If you want more TB messages in dmesg to see why connection might be failing here is how to turn on dynamic tracing

For bootime you will need to add it to the kernel command line by adding thunderbolt.dyndbg=+p to your /etc/default/grub file, running update-grub and rebooting.

To expand the example above"

`GRUB_CMDLINE_LINUX_DEFAULT="quiet intel_iommu=on iommu=pt thunderbolt.dyndbg=+p"`  

Don't forget to run update-grub after saving the change to the grub file.

For runtime debug you can run the following command (it will revert on next boot) so this cant be used to cpature what happens at boot time.

`echo -n 'module thunderbolt =p' > /sys/kernel/debug/dynamic_debug/control`

install tbtools

these tools can be used to inspect your thundebolt system, note they rely on rust to be installedm you must use the rustup script below and not intsall rust by package manager at this time (9/15/24)

apt install pkg-config libudev-dev git curl
curl https://sh.rustup.rs -sSf | sh
git clone https://github.com/intel/tbtools
restart you ssh session
cd tbtools
cargo install --path .
@scyto
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scyto commented Aug 8, 2025

Have you tried to kill the frr setup and move to the SDN way as described here? https://gist.github.com/taslabs-net/9da77d302adb9fc3f10942d81f700a05

I am closely monitoring this progress before I will upgrade 🫣

ok just looked at before starting work, love the use of EOF in it in general, not sure why they are enabling systemd networking - if thats an official proxmox prereq, great, if not i have had experience of using tradtional networking (interfaces file) / systemd / network manager and one never wants both of them enabled at same time, it will end in tears, i never had to explicitly do that and the big one - no i won't be using it, it is a n IPv4 only solution, i run full dual stack and use IPv6 only for cpeh (and i have no plans to change to that because of hpw IPv6 solves certain IPv4 issues in how machines find each other).

I will be moving to SDN (which is FRR when the more advanced modes are used) when it can support IPv6 and that is dependent on changes in upstream ifupdown2 package, or proxmox just choosing to permaently fork it (the patch has been ready for 9mo)

@scyto
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scyto commented Aug 8, 2025

All I have time to do is watch for now unfortunately and likely a proper solution will be in place by the time I do have time freed up next week.

welcome, i am staying away from SDN until i see the needed patch, i am confident the network hang at boot is because at interface up its causing something to run that restarts frr or does some other action that is in my gists or someone suggested in the comments and you implemented

as such it sholuld be incredibly easy to figure out what - you have the service timing out, when it times out it is hard killes and should (may?) write the stack trace of the scheduler.py script at that poin - this should give an idication of what hung if it is not the same thing as I am seeing

it's also possible we don't even the frr restart scripts, remeber this 9.x we know all the network services have been rebuilt and use higher level version, it could be we no longer need to keep restarting frr.service each time we take up and down interfaces.... it might be that we can use the pve network command line to do that instead (instead of restarting frr.service just repapply proxmox networking

@scyto
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scyto commented Aug 8, 2025

i added a reddit PSA here if any of you are redditors and want to mop others who hit the issue (not eveyone looks at these gist comments)

https://www.reddit.com/r/Proxmox/comments/1mkz0jg/psa_upgrade_to_9_and_thunderbolt_mesh_issues/

@Randymartin1991
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ou can also turn on ehanced TB debugging to see via dmesg what is happening at the tb layer physically in terms of negotiation, there are some sliding windows on tb negotiation that can impact perf, i do have a note from the tb developer how to modify that (allocate more fixed tb bandwdith to one domain)

Did a TB cable pull, however issue is still the same. I am running an ipv4 setup, maybe better to go for ipv6. I never got this stable for a long time. max a few weeks then the speeds drops. But after my failed update, is fails on one specific node within 30 minutes.

@ratzofftyoya
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Very much looking forward to the official IPv6-capable @scyto guide! I am probably one of the first people to try doing this for the first time on a PVE9 install...probably just shouldn't have upgraded before attempting....So on step 1 I was like "/etc/modules is obsolete....hmmmm" :)

@Randymartin1991
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ou can also turn on ehanced TB debugging to see via dmesg what is happening at the tb layer physically in terms of negotiation, there are some sliding windows on tb negotiation that can impact perf, i do have a note from the tb developer how to modify that (allocate more fixed tb bandwdith to one domain)

Did a TB cable pull, however issue is still the same. I am running an ipv4 setup, maybe better to go for ipv6. I never got this stable for a long time. max a few weeks then the speeds drops. But after my failed update, is fails on one specific node within 30 minutes.

Alright sorry for me spamming this thread with my speed issues. I Think I maybe found the issue. I moved a heavy VM to a diffrent node. Now the speed is constant on 25/gbs and dont have the drop anymore. I think it has something to do with heat. Becauese the VM creates more CPU stress, it generates more heat and perhaps throttling comes into play. Will keep an eye on it today. Thanks again.

@ssavkar
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ssavkar commented Aug 9, 2025

When you upgrade to Squid, I can do that on each node, and it'll connect to the other nodes running the previous version without any problems? Then once all are running on Squid, then do the upgrade?

hi just to follow up on the Squid update, I am now in the process of updating my other 3-node proxmox cluster to squid from quincy. Just went from quincy to reef and about to swap up to squid. Super easy. If you open three shells for each of your three machines, just follow the directions in the links I gave you, and you should be perfect!

@Allistah
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Thanks @ssavkar - I've got my three nodes all upgraded to Squid. Now I need to update to v9. Who has done that successfully so far?

@Randymartin1991
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I found the solution to the unreliable speed issues, with my miniforums MS-01. It turns out some BIOS settings. Make sure all ASMP is disabled for all pci devices and force the pci speed to gen4.
I also disabled CPU C-states. Now it is running consistently 25gb/s instead of randomly dropping to 7gb/s.
This took a few weeks of my live, but hey, where here now. :D

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