Are you sure it's not a routing problem? Are you able to PING different IPs both ways?
In default PVE installation, pveproxy listens on tcp/8006 port on all interfaces, so it should not be a case.
To be honest, some diagram would be great here ;-)
Site A (York):
-Router 10.10.100.1 (OpenWRT)
-WG interface IP 10.10.120.1
-WG interface peer (for site b) allowed ips: 10.10.120.12/32, 10.10.125.0/2 0 + route allowed peers
-Proxmox Host 10.10.100.8
-Site A arbitrary machine 10.10.100.105
-vmbr0 bridged to wan
-vmbrSwitch configured with all vlans, including .100 - interfaced through openwrt
Site B (Union):
-Router 10.10.125.1 (OpenWRT)
-WG interface IP: 10.10.120.12
-WG Peer (Peer back to Site A) allowed ips: 0.0.0.0/0, ::/0 - route allowed ips
-Proxmox host 10.10.125.100
-VM on proxmox: 10.10.125.225
-vmbr0 bridged to ethernet going back to wan (Actually a TP Link Deco router - 51820 ports forwared, unpnp disabled, sip alg disabled)
-vmbrYork - dumb switch attached openwrt
Static Routes (Site A - OpenWRT)
- 10.10.125.0/24 (Target) -> 10.10.125.12 (Gateway)
Static Routes (Site B - OpenWRT)
-10.10.100.0/24 (Target) -> 10.10.120.1 (Gateway)
Static Routes (Site B - TP Link)
-10.10.125.0 -> 192.168.68.58 (Openwrt Site B on tp link lan)
Routes (Site B - Proxmox Host) - I had to add a couple routes to get back to 10.10.100.1/24 subnet from proxmox host:
-10.10.100.0/24 via 10.10.125.1 dev vmbrYork
-10.10.125.0/24 via vmbrYork proto kernel scope link src 10.10.125.100
-192.168.68.0/24 dev vmbr0 proto kernel scope link src 192.168.68.222
Working:
-Site A devices can ping Site B peer IP
-Site A devices can ping Site B VM (10.10.125.225)
-Site A devices can access Site B router via 10.10.125.1
-Site B devices/VMS can access proxmox host management on 10.10.125.100 and ping it
-Site B (proxmox host and VMs) can access ALL devices back on Site A
-Site B proxmox host tcpdump -i vmbrYork SEES pings attempting to reach 10.10.125.100 as they hit openwrt, but fail to reach it itself
Not Working:
-Cannot ping 10.10.125.100 from Site A (Immediate icmp request time out)
-Cannot reach it in browser
-I've tried messing with firewall rules, but it should all be set to allow traffic here.. plus all the rest of Site A <-> Site B is working.
-Tried disabling rp filter on vmbrYork
The only thing I can think of is that the proxmox host on site b is incorrectly on the subnet? (although it works from machines on Site B)
I followed suggestions of chat bots for a little and started messing with mss clamping and mtu, only before temporarily breaking the site to site Vpn
Site B etc/network/interfaces
auto vmbr0
iface vmbr0 inet static
address 192.168.68.222/24
gateway 192.168.68.1
bridge-ports enp1s0
bridge-stp off
bridge-fd 0
auto vmbrYork
iface vmbrYork inet static
address 10.10.125.100/24
bridge-ports none
bridge-stp off
bridge-fd 0
post-up ip route add 10.10.100.0/24 via 10.10.125.1
Sorry to bring this post alive so much later. Thanks for any advice. I'd dump more information about site b host, but I have to manually type the output because of how I am connected to that machine (console on a browser through a rdp through an rdp)