[SOLVED] MTU across public IPs and Bridges with vxlan

[albans]

Hi,

Quick question as I'm getting some timeout on PMG after DATA(0), and I read that some other members have experienced the same due to MTU wrongly set.
In summary, PMG is behind NAT -> public proxmox host IP vmbr0 with MTU 1500, and private PMG IP vmbr1 with MTU 1450. Is there anything wrong with this?

Seems to be expected: https://pve.proxmox.com/pve-docs/chapter-pvesdn.html#pvesdn_setup_example_vxlan
VXLAN zone configuration options:
Peers Address List
A list of IP addresses of each node in the VXLAN zone. This can be external nodes reachable at this IP address. All nodes in the cluster need to be mentioned here.

MTU
Because VXLAN encapsulation uses 50 bytes, the MTU needs to be 50 bytes lower than the outgoing physical interface.

Thank you for your thoughts.

 

[albans]

FYI - the current MTU are setup automatically by Proxmox.

Shall I force MTU 1450 on the eth0 interface of the proxmox host?

Or increase my vxlan MTU and all LXC/VM veth to 1550?

 

[albans]

I worked around the issue by creating an additional bridge local to the proxmox host (not part of any vxlan), then adding a veth to the LXC being NAT, and used that veth for the NAT forwarding rule. I noted that the local bridge has by default a MTU of 1500, same as eth0, hence probably avoiding the issue with NAT to a veth and a different MTU imposed by vxlan overhead.

Please, comment in case you've other approaches that may work without the additional proxmox host local bridge.