[LXD] BGP address/route advertisement

[tomp (Thomas Parrott)]

@stgraber I do have one more question regarding the external routes on a bridged NIC.

@stgraber

External addresses/subnets routed to a specific instance on a bridged network

With this case, the instances will likely be running on private addressing with LXD’s dnsmasq in charge of assigning addresses. LXD will look for ipv4.routes.external and/or ipv6.routes.external to know what needs to be routed to the instance, will then setup a suitable route on the host (same as ipv4.routes or ipv6.routes) and finally will advertise a route to the host over BGP.

With the equivalent settings on an OVN NIC, the external routes are routed in OVN to the specific NIC’s IP using the OVN allocated (or statically defined) IP address on the NIC. These are always available and are statically allocated by OVN, even if not specifically specified by the user.

In comparison the bridged NICs don’t always have an IP allocated, and it can change during the NICs lifetime via DHCP lease changes.

Should we require a force/require a static allocation for NICs using this feature, like we do with IP filtering and proxy NAT mode? So that we have a specific target IP for the host side routes?

Also, are there any considerations regarding fan networks? I think it would be OK as each LXD server will have its own local subnet on the fan that it can advertise independently of the overall fan subnet.