Help on implementing Proxmox in KS-5 servers

Jovanfever · November 2025

I m looking for the possibility of implementing Proxmox in KS-5 servers, But will it support ipv6 based VMs? Can we get ipv6 /64 in KS-5?
Anyone tried this?

RickBakkr · November 2025

I am guessing the trick of using nddpd will still work ;-)

oloke · November 2025

Hi!

I've also been researching this topic in the past couple days. I will post some links to sources I used so far. However I'm still unable to get it to work. If you have any luck please let me know.

In general, I think we get the whole /64 but it's not routed so you need to run an NDP proxy daemon to respond on the entire subnet (for VMs).

Homwer · November 2025

Be sure that have an ipv6 /64 routet through the network.
Not all KS machines have!

Try to give your vmbr0 the ipv6 config from OVH with the /128 address.
Be sure that ipv6 works!

Change the ::1/126 to ::2 /64

Accept the change, if you can reach ipv6 adresses you have a full /64. If not - bad server.
Nothing you can do about it. Get a refund and a new server.

If it works with ::2
Do this

apt install ndppd

route-ttl 30000
proxy vmbr0 {
router yes
timeout 500
ttl 30000
rule 2001:41d0:8:aaaa::/64 { <--- Edit that to your ipv6 
static
}
}

Enable ipv6 forewarding

echo 1 > /proc/sys/net/ipv6/conf/all/forwarding

Give your VM on vmbr0 any address from the :: /64 and use the proxmox host as gateway!

barbarza · November 2025

@RickBakkr said:
I am guessing the trick of using nddpd will still work ;-)

I don't know why but getting IPv6 proxying working on my new KS-LE-B was a much bigger mission than it was on my KS-Mystery. OVH must have changed something...

nghialele · November 2025

Wow, thank you all for sharing your takes, watching this thread!

loay · November 2025

Created this with Opus 4.5

https://gist.github.com/loayai/8eb1fa456246202a4deece7780725da6

Example output :

━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
  IPv6 /64 Access Verification
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━


▶ Detecting IPv6 Configuration
────────────────────────────────────────────────────────────────────────
  ℹ Interface: eno1
  ℹ Primary IPv6: 2001:41d0:x:xxxx::1/128
  ℹ Your /64 block: 2001:41d0:x:xxxx::/64
  ℹ Gateway: 2001:41d0:x:xxff:ff:ff:ff:ff
  ✓ IPv6 connectivity confirmed
  ℹ Generated 3 test addresses

▶ Testing /64 Address Space
────────────────────────────────────────────────────────────────────────

  Testing (1/3): 2001:41d0:x:xxxx::7e57:1
  ✓ Added to interface
  ✓ Address is active

  Testing (2/3): 2001:41d0:x:xxxx::7e57:2
  ✓ Added to interface
  ✓ Address is active

  Testing (3/3): 2001:41d0:x:xxxx::7e57:3
  ✓ Added to interface
  ✓ Address is active


▶ Testing Outbound Connectivity from New Addresses
────────────────────────────────────────────────────────────────────────

  From: 2001:41d0:x:xxxx::7e57:1
  ✓ Outbound connectivity works

  From: 2001:41d0:x:xxxx::7e57:2
  ✓ Outbound connectivity works

  From: 2001:41d0:x:xxxx::7e57:3
  ✓ Outbound connectivity works

▶ NDP Proxy Requirement Check
────────────────────────────────────────────────────────────────────────
  ℹ NDP proxy is disabled (will need for VMs)
  ℹ IPv6 forwarding is disabled (will need for VMs)
  ℹ ndppd not installed (required for VM IPv6)

  Note on Inbound Traffic:
  OVH uses NDP instead of routing your /64. This means:
  • Inbound traffic to VM addresses requires NDP proxy
  • Without ndppd, VMs won't receive incoming IPv6 traffic
  • Outbound from VMs may work but replies won't return

━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
  SUMMARY
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  Your IPv6 Block:  2001:41d0:x:xxxx::/64
  Addresses Tested: 3
  Successfully Added: 3

  ✓ /64 ACCESS CONFIRMED
  You can use the full /64 block for your VMs!

  Available range:
  2001:41d0:x:xxxx:: through 2001:41d0:x:xxxx:ffff:ffff:ffff:ffff

━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
  NEXT STEPS FOR PROXMOX
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  1. Install NDP Proxy daemon:
     apt install ndppd

  2. Configure /etc/ndppd.conf:
     ┌────────────────────────────────────────────────────┐
     │ route-ttl 30000                                    │
     │ proxy vmbr0 {                                      │
     │   router yes                                       │
     │   timeout 500                                      │
     │   ttl 30000                                        │
     │   rule 2001:41d0:x:xxxx::/64 {                     │
     │     static                                         │
     │   }                                                │
     │ }                                                  │
     └────────────────────────────────────────────────────┘

  3. Enable IPv6 forwarding:
     echo 1 > /proc/sys/net/ipv6/conf/all/forwarding

     For persistence, add to /etc/sysctl.conf:
     net.ipv6.conf.all.forwarding = 1

  4. Start ndppd:
     systemctl enable --now ndppd

  5. VM Configuration:
     • Bridge: vmbr0
     • IPv6: Any address from 2001:41d0:x:xxxx::/64
     • Gateway: 2001:41d0:x:xxxx::1 (Proxmox host)

  Example VM config:
     IPv6 Address: 2001:41d0:x:xxxx::100/64
     IPv6 Gateway: 2001:41d0:x:xxxx::1

kenjing789 · November 2025

I just setup a Proxmox node recent on old KS-LE-A. Normally the issue come from Proxmox Host Firewall if u set drop all inbound by default and the VM have Firewall enable.
Create a vmbr1, set ndppd on vmbr1, use Proxmox Host as gateway, enable forward and profit.

risharde · November 2025

Hmmm, I thought I read somewhere that the kimsufis only come with one ipv6 now, maybe I read wrong.

tux · November 2025

maybe SYS servers are easier to setup.

Jovanfever · November 2025

@kenjing789 said:
I just setup a Proxmox node recent on old KS-LE-A. Normally the issue come from Proxmox Host Firewall if u set drop all inbound by default and the VM have Firewall enable.
Create a vmbr1, set ndppd on vmbr1, use Proxmox Host as gateway, enable forward and profit.

Can we create vmbr1 when vmbr0 is still there? vmbr0 still have that ipv6 gateway right? I am unable to create vmbr1 with the same ipv6 gateway.

kenjing789 · November 2025

@Jovanfever said:

@kenjing789 said:
I just setup a Proxmox node recent on old KS-LE-A. Normally the issue come from Proxmox Host Firewall if u set drop all inbound by default and the VM have Firewall enable.
Create a vmbr1, set ndppd on vmbr1, use Proxmox Host as gateway, enable forward and profit.

Can we create vmbr1 when vmbr0 is still there? vmbr0 still have that ipv6 gateway right? I am unable to create vmbr1 with the same ipv6 gateway.

Oh yes i forgot the most main point to make this work.
You need disable auto_ra on vmb0 and vmbr1, why ? idk but after do it those ip working. After that you need dnsmasq or DHCP VM, i use OpenWRT VM for this.
Also remember enable ip forward and ndp proxy on sysctl

here my interfaces

auto vmbr0
iface vmbr0 inet static
address 94.23.xx.xx/24
gateway 94.23.xx.xx
bridge-ports eno1
bridge-stp off
bridge-fd 0
hwaddress xx:xx:xx:xx:C5:3A

iface vmbr0 inet6 static
address 2001:41d0:xxxx:xxxx::1/128
gateway 2001:41d0:xxxx:xxff:ff:ff:ff:ff

auto vmbr1
iface vmbr1 inet static
address 10.10.0.1/24
bridge-ports none
bridge-stp off
bridge-fd 0
# IPv4 NAT rules
post-up echo 1 > /proc/sys/net/ipv4/ip_forward
post-up iptables -t nat -A POSTROUTING -s 10.10.0.0/24 -o vmbr0 -j MASQUERADE
post-down iptables -t nat -D POSTROUTING -s 10.10.0.0/24 -o vmbr0 -j MASQUERADE

iface vmbr1 inet6 static
address 2001:41d0:2:xxxx:1::1/64
# IPv6 routes for VM subnet
post-up ip -6 route add 2001:41d0:2:xxxx:1::/64 dev vmbr1
post-down ip -6 route del 2001:41d0:2:xxxx:1::/64 dev vmbr1
accept_ra 0
autoconf 0

and sysctl file

root@ns369568:/etc/sysctl.d# cat 99-vm-forwarding.conf

IPv4 forwarding for NAT

net.ipv4.ip_forward=1
net.ipv4.conf.all.forwarding=1

IPv6 forwarding for routing

net.ipv6.conf.all.forwarding=1
net.ipv6.conf.default.forwarding=1

IPv6 NDP proxy (required for OVH)

net.ipv6.conf.all.proxy_ndp=1
net.ipv6.conf.default.proxy_ndp=1

Disable IPv6 autoconfiguration on bridges

net.ipv6.conf.vmbr0.autoconf=0
net.ipv6.conf.vmbr0.accept_ra=0
net.ipv6.conf.vmbr1.autoconf=0
net.ipv6.conf.vmbr1.accept_ra=0

Howdy, Stranger!

Categories

In this Discussion

Help on implementing Proxmox in KS-5 servers

Comments

IPv4 forwarding for NAT

IPv6 forwarding for routing

IPv6 NDP proxy (required for OVH)

Disable IPv6 autoconfiguration on bridges

Howdy, Stranger!

Quick Links

Categories

In this Discussion

Help on implementing Proxmox in KS-5 servers

Comments

IPv4 forwarding for NAT

IPv6 forwarding for routing

IPv6 NDP proxy (required for OVH)

Disable IPv6 autoconfiguration on bridges