[pve-devel] [PATCH v4 cluster/network/manager/qemu-server/container/docs 00/33] Add support for DHCP servers to SDN

DERUMIER, Alexandre alexandre.derumier at groupe-cyllene.com
Tue Nov 21 14:02:38 CET 2023

>>I tested the DHCPv6 setup now and unfortunately it does not work
>>I have a VNet with both IPv4 and IPv6 subnets.
>>The IPAM part works correctly, registering both IPv4 and IPv6.
>>In the VM I can get an IPv4 from the DHCP but IPv6 does not work.
>>I only get a /128 address but I configured a /64 subnet.

Yes, this is expected with dhcpv6. It's always /128 mask, and all
traffic is forwarded through the local-link if you have a RA.

I have talked about this with other network admin, this is the way
how dhcpv6/RA is implemented.

It can't be use like dhcp4 to send classic routes. (it don't even sent
network mask, on the ip)

The only way is to use static configuration, or hack dhcp protocol,
sending dhcpv6 custom options + a dhclient script on the vm guest side,
parsing theses options and setting config statically.

with slaac, it should always give you a /64 , but this is the same
problem with RA.

RA has been invented for mobile/desktop client, forcing all traffic
through the local-link.
For server, to use true gateway, ipv6 should be set statically.

More information about the pve-devel mailing list