Unstable Networking in LXC Container

[hbau]

Dear All,

i have a verry strange phenomenon, on which i need help...
I have a Proxmox VE 8.4.1 up and running.
Now i set up a Ubuntu 25 LXC Container.

On this container the Networking / Internetconnectivity just doesn`t work stabel.
Meaning: one time ist working the other time e.g. after a reboot, its not.

once i get it working again after pinging other divices on the network, but no (nothing changed) i cant reach the gateway.

I can ping the host IP of Proxmox VE. 192.168.x.6
I can ping another LXC (Promox Mail Gateway) 192.168.x.8

i can't ping the Gateway: 192.168.x.1

after fresh install i could resolve ubuntu.com so configuation seemd ok.=> updatingthe system and installing some stuff.... all fine.

On the host (PVE) a added to /etc/pve/lxc/id.conf these lines:

lxc.cgroup2.devices.allow: c 10:200 rwm
lxc.mount.entry: /dev/net dev/net none bind,create=dir

Networksetting of Container are:
eth0 on vmbr0 no firewall IPaddress: 192.168.x.11/24 Gateway 192.168.x.1
DNS is set to 1.1.1.1

i can ping the LXC Container from the PVE Host, but i takes a while untill the Ping reaches througgh...

I am at a total loss, on what i am missing, that i can get the connectivity to the gateway...

An hints? suggestiones?

Thank you in advance.
HBau