Thanks to
spirit, I managed to get this EVPN-VXLAN system to work so here is a how-I-did-it.
Assuming a router with a LAN IP of 192.168.1.1 and 3x Proxmox VE host nodes as pve1 (192.168.1.21), pve2 (192.168.1.22) and pve3 (192.168.1.23) including a number of VM/CTs in an internal 10.1.1.0/24 network all being able to see each other across the PVE host nodes including all upstream 192.168.1.0/24 LAN hosts and the general internet.
1. Goto Datacenter > SDN > Options and add a 'evpn' Controller with ID: evpnctl, ASN #: 65000 and Peers: 192.168.1.21, 192.168.1.22, 192.168.1.23
2. Goto Zones and Add a EVPN item with ID: evpn1, Controller: select evpnctl, VRF-VXLAN Tag: 10000, Exit Nodes: select pve1 pve2 pve3, Primary Exit Node: select pve1, MTU: 1450
3. Goto VNets and Create one with Name: vnet1, Zone: evpn1, Tag: 20000
4. Over in Subnets to the right, create a new one with Subnet: 10.1.1.0/24, Gateway: 10.1.1.1, SNAT ticked
5. That's mostly it so go back to SDN and click Apply
6. Create a Debian LXC container and set Network > Edit net0 to Bridge: select vnet1, IP Address: 10.1.1.2/24, Gateway: 10.1.1.1.
7. Shutdown and clone 2 more CTs and move them to the other two host nodes with IPs of 10.1.1.3/24 and 10.1.1.4/24 IPs, plus Gateway: 10.1.1.1 for both (I called my test CTs ctd1, ctd2 and ctd3 with 200Mb ram and 2Gb storage for super fast cloning and backup)
8. Goto your 192.168.1.1 router and create a static route with Network/Host: 10.1.1.0, Netmask: 255.255.255.0, Gateway: 192.168.1.21, Metric: 1, Interface: LAN
That's it. Maybe reboot the primary pve1 host node (that's when it started working for me, maybe coincidence) and please reply here with any success or corrections. Obviously change the IPs and hostnames to suit your cluster layout. Here are some commands I found useful...
Code:
iptables -t nat -L -vnx
tcpdump -nvi vmbr0 host 1.1.1.1
cat /etc/network/interfaces
cat /etc/frr/frr.conf
cat /etc/pve/sdn/*
vtysh -c "show bgp summary"
ip nei (and of course ip a, ip r)
TODO: dynamic BPG exit nodes to get around any single primary exit node downtime and DHCP allocation of 10.1.1.0/24 IPs for VM/CTs using Bridge: vnet1 so if anyone could add a step by step guide how-to-do-that within this network scenario then it would be hugely appreciated.